Environmental Science Environmental Geology
Ellen Wohl
  • LAST MODIFIED: 24 May 2017
  • DOI: 10.1093/obo/9780199363445-0072


Environmental geology involves application of geological knowledge to the investigation of processes occurring at or near Earth’s surface in order to mitigate natural hazards and minimize environmental degradation. Environmental geology commonly focuses on four primary components. The first involves identifying and managing natural hazards, including earthquakes, floods, hillslope instability, soil erosion, subsidence, volcanoes, and wildfires. The second primary component of environmental geology involves managing use of natural resources such as minerals, soil, and water. A third component involves managing energy sources such as coal and oil to mitigate hazards and enhance sustainability. The final component relates to managing disposal of wastes such as radioactive materials or excess nutrients and investigates contaminant dispersal through erosion and deposition. Environmental geology has largely developed as a subdiscipline within geology since the 1970s, although research related to natural hazards, in particular, dates to the founding of geology as a discipline during the 18th century. The first textbook of environmental geology was published in 1982 by an American author, and courses in the subject are now widely taught in universities within the United States and throughout the world. Some of the components of environmental geology overlap with engineering geology. Engineering geologists apply geological knowledge to engineering in order to ensure that geological factors are recognized and accounted for when designing, siting, and constructing infrastructure such as roads and buildings. Engineering geologists assess potential geological hazards such as hillslope instability, erosion, and flooding, which creates overlap with environmental geology. In practice, many individuals engaged in these fields consider themselves to be both environmental and engineering geologists.

Reference Works

Reference works on environmental geology are notably lacking. Alexander and Fairbridge 1999 provides a thorough and useful encyclopedic treatment of the topic, although many entries are now dated.

  • Alexander, D. E., and R. W. Fairbridge, eds. 1999. Environmental geology. Encyclopedia of Environmental Science. The Netherlands: Springer.

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    Encyclopedia with 374 entries from acid corrosion to zoning regulations; entries written by experts in the topic; provides short overviews of diverse aspects of environmental geology.

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Textbooks explicitly focused on environmental geology start with the first edition of Keller (1982). The ninth edition of this text, Keller 2011, is now in use. Other primary textbooks include Keller 2012, which is a lower-level introduction to environmental geology; Montgomery 2008; and Merritts, et al. 2014. The topics covered in each of these textbooks are very similar, although the level of the writing and assumed background knowledge varies among them. Natural hazards are a large part of environmental geology, and textbooks focused specifically on natural hazards include Keller and DeVecchio 2014 and Hyndman and Hyndman 2014. All of these are primarily introductory textbooks. The lack of advanced textbooks may reflect both the breadth and the comparatively recent development of environmental geology as a distinct subdiscipline within geology. Bell 1998 represents a more advanced textbook written with more of an engineering geology focus, despite the title.

  • Bell, F. G. 1998. Environmental geology: Principles and practice. Chichester, UK: Wiley Blackwell.

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    Advanced textbook for upper-level undergraduate and graduate students; covers environmental hazards such as volcanoes and earthquakes, as well as environmental problems such as mining and waste disposal; examples and case studies from around the world.

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  • Hyndman, D., and D. Hyndman. 2014. Natural hazards and disasters. 5th ed. Boston: Cengage Learning.

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    Introductory level text for nonscience majors; covers processes and natural hazards associated with plate tectonics, earthquakes, tsunamis, volcanoes, landslides, subsidence and shrink-swell soils, weather, climate change, floods, coastal processes, cyclones, fires, and extraterrestrial impacts.

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  • Keller, E. A. 2011. Environmental geology. 9th ed. Upper Saddle River, NJ: Pearson.

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    Starts with basics of Earth materials and processes, along with ecosystems; second part devoted to hazardous processes from flooding, landslides, earthquakes, volcanoes, coastal hazards, and extraterrestrial impacts; third part covers resources and pollution with respect to water, minerals, and energy; the final part covers climate change and society.

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  • Keller, E. A. 2012. Introduction to environmental geology. 5th ed. Upper Saddle River, NJ: Pearson.

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    Designed for nonscience majors; focuses on human population growth, sustainability, Earth as a system, hazardous Earth processes, and scientific knowledge and values.

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  • Keller, E. A., and D. E. DeVecchio. 2014. Natural hazards: Earth’s processes as hazards, disasters, and catastrophes. 4th ed. New York: Routledge.

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    Introductory text that covers processes and hazards associated with earthquakes, tsunamis, volcanoes, flooding, hillslope instability, subsidence and soils, severe weather, cyclones, coastal hazards, climate change, wildfire, and extraterrestrial impacts and episodes of mass extinction.

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  • Merritts, D., K. Menking, and A. DeWet. 2014. Environmental geology: An Earth systems approach. 2d ed. New York: Freeman.

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    Emphasizes an Earth systems approach; covers dynamic Earth systems and sustainability; solid Earth; earthquakes; Earth materials; geologic time and rates of change; the biosphere and ecosystem services; volcanoes; surface and ground water; atmosphere and weather; oceans and coasts; energy; climate and environmental change; the Anthropocene.

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  • Montgomery, C. W. 2008. Environmental geology. 10th ed. New York: McGraw-Hill.

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    Introductory level; includes basics of Earth history, structure, and composition; human population growth and impacts; natural hazards from earthquakes, volcanoes, floods, hillslope instability, coastal processes, and climate change; resources of water, soil, minerals, rock, fossil fuels, and alternative energy sources; waste disposal, water and air pollution, environmental law and policy, and land-use planning and engineering geology.

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As with reference works, bibliographies of environmental geology are limited in number and not recently updated. Both Hall 1975 and Richner 1981 are thorough but very dated.


The works cited in this section are journals that address all aspects of environmental geology, including Environmental Earth Sciences, Journal of Environmental Management, and Environmental Management; journals that address diverse types of natural hazards, including International Journal of Disaster Risk Science, Geoenvironmental Disasters, Natural Hazards, and Journal of Geography and Natural Disasters; and journals that focus on a particular type of natural hazard, as in the Journal of Applied Volcanology.

Natural Hazards

A natural hazard is a naturally occurring event that may have a negative effect on people, human communities and built infrastructure, or on the environment. Examples include intense storms, volcanic eruptions, earthquakes, tsunamis, or wildfires. Such natural events can create opportunities for ecosystems and biotic communities by enhancing habitat diversity, making new resources available, and facilitating dispersal of organisms, but they can also stress biotic communities. In the context of people, property, and infrastructure, natural processes create hazards through injury and death to people and damage to property and infrastructure. Environmental geologic approaches to natural hazards include identifying factors that promote and limit the occurrence of hazardous processes; characterizing the (pre)historical occurrence and characteristics of hazards; and designing systems to limit the effects of natural hazards, such as sediment detention basins, early warning systems for floods, or mapping of debris-flow paths and zoning of land use. Subheadings under natural hazards address twelve distinct types of natural hazards.

Climate Change

As global climate warms, many secondary effects are creating hazards, such as melting glaciers that release water, causing global sea level to rise, which in turn allows storm surges to reach farther inland, or more frequent and prolonged droughts that stress trees, making forests more susceptible to insect infestations and wildfires. Evans and Clague 1994 reviews diverse secondary hazards resulting from glacial retreat in mountainous regions. More direct hazards resulting from climate change include alterations in the magnitude, frequency, and duration of extreme conditions, such as drought, extreme precipitation, and cyclones. Environmental geology provides a longer-term perspective on the magnitude, frequency, and duration of these extremes during the Holocene Epoch, which is the last ten thousand years of geologic time. This period, since the melting of the great continental ice sheets, is widely used as an indicator of climate fluctuations in the absence of human-induced changes in atmospheric chemistry. Environmental geologists use records of past environments as preserved in tree rings, fossils, glacial ice, and sediments to infer changes in climate during the Holocene, as well as the secondary effects of changing climate on natural processes such as drought, floods, or wildfire. Tree rings were one of the first features systematically studied as indicators of past climate, and Fritts 1976 provides a historical review of the development of this research. Gholami, et al. 2016 provides a recent example of using tree rings to reconstruct past climate in a specific region. Corals also develop annual growth rings with characteristics that reflect environmental conditions, as illustrated by the use of nearshore corals to infer flood history in Leonard, et al. 2016. Other examples of geologic records of past climatic conditions include Brown, et al. 2000, which reconstructs ten thousand years of flood occurrence from lake sediments, and Cuffey, et al. 2016, which uses the isotopic composition of air bubbles trapped in glacial ice to infer past surface temperatures. Sealy, et al. 2016 uses changes in tooth enamel of fossilized herbivorous animals to infer changes in vegetation communities and climate. Lorrey and Bostock 2017 exemplifies regional paleoclimatic reconstructions, which commonly use information from multiple types of records.

  • Brown, S. L., P. R. Bierman, A. Lini, and J. Southon. 2000. 10,000 yr record of extreme hydrologic events. Geology 28:335–338.

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    Lake sediments from northern Vermont, United States, containing fifty-two distinct sediment layers associated with floods indicate fluctuations in frequency and magnitude of floods during the past ten thousand years; the recurrence interval of floods averages 130 years during stormy periods such as older than 8600, 6330 to 6840, and 1750 to 2620 years ago.

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  • Cuffey, K. M., G. D. Clow, E. J. Steig, et al. 2016. Deglacial temperature history of West Antarctica. Proceedings of the National Academy of Sciences of the United States of America 113:14,249–14,254.

    DOI: 10.1073/pnas.1609132113Save Citation »Export Citation »E-mail Citation »

    Summarizes use of ice-core data to reconstruct the surface temperature history of West Antarctica; atmospheric composition is inferred using the isotopic composition of hydrogen and nitrogen in air bubbles trapped within the glacial ice.

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  • Evans, S. G., and J. J. Clague. 1994. Recent climate change and catastrophic geomorphic processes in mountain environments. Geomorphology 10:107–128.

    DOI: 10.1016/0169-555X(94)90011-6Save Citation »Export Citation »E-mail Citation »

    Effective overview of natural hazards in mountainous regions as a result of warming climate; hazards addressed include glacier ice loss and resulting glacier avalanches, slope failures caused by glacier debuttressing, outburst floods from glacier-dammed lakes, and changes in water and sediment supply induced by glacier retreat.

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  • Fritts, H. C. 1976. Tree rings and climate. London: Academic Press.

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    One of the earliest comprehensive summaries of the types of climatic and hydrological information that can be gleaned from tree rings; discusses the historical development of dendrochronology, or the study of tree rings, as well as the basic physiological processes of trees and how climate affects these processes and leaves a record in tree rings.

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  • Gholami, V., M. A. Jolandan, and J. Torkaman. 2016. Evaluation of climate change in northern Iran during the last four centuries by using dendroclimatology. Natural Hazards 85.3: 1835–1850.

    DOI: 10.1007/s11069-016-2667-4Save Citation »Export Citation »E-mail Citation »

    A recent example of using tree-ring records to infer climate change for a region; tree rings indicate that significant changes occurred in the mid-20th century as the region under study changed from semiarid to arid and annual precipitation decreased substantially.

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  • Leonard, N. D., K. J. Welsh, J. M. Lough, et al. 2016. Evidence of reduced mid-Holocene ENSO variance on the Great Barrier Reef, Australia. Paleoceanography 31:1248–1260.

    DOI: 10.1002/2016PA002967Save Citation »Export Citation »E-mail Citation »

    Uses luminescence intensity of annual growth rings in reef corals to infer variations in rainfall that affect river discharge, which brings terrestrial organic acids into nearshore environments where corals can take up the organic material; results indicate that El Nino–Southern Oscillation climate events have become more frequent and extreme since the early 20th century.

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  • Lorrey, A. M., and H. Bostock. 2017. The climate of New Zealand through the Quaternary. In Landscape and Quaternary environmental change in New Zealand. Edited by J. Shulmeister, 67–139. Amsterdam: Atlantis.

    DOI: 10.2991/978-94-6239-237-3_3Save Citation »Export Citation »E-mail Citation »

    An example of using diverse geologic records of past climate to understand the direction and rate of changes in temperature and precipitation; this study combines marine sediments, pollen records from terrestrial environments, and glacial chronologies based on cosmogenic isotope dating of glacial sediments.

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  • Sealy, J., J. Lee-Thorp, E. Loftus, J. T. Faith, and C. W. Marean. 2016. Late Quaternary environmental change in the Southern Cape, South Africa, from stable carbon and oxygen isotopes in faunal tooth enamel from Boomplaas Cave. Journal of Quaternary Science 31:919–927.

    DOI: 10.1002/jqs.2916Save Citation »Export Citation »E-mail Citation »

    Investigators used carbon isotopic ratios in the tooth enamel of animal fossils at an archeological site to infer changes in proportions of different types of vegetation that are sensitive to changes in seasonal distribution of rainfall.

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Coastal Processes

Natural hazards associated with coastal processes include erosion of coastlines, whether this takes the form of retreat of coastal cliffs or removal of sand from beaches and exposure of the underlying bedrock. Retreat of coastal cliffs has been particularly rapid since the mid-20th century in Arctic environments, where thawing permafrost combines with receding sea ice to maximize coastal erosion, as discussed in Mars and Houseknecht 2007. Erosion of beach sand has triggered artificial beach replenishment in many areas during recent decades, and one of the world’s leading experts on coastal processes critically examines the effects of beach replenishment in Pilkey 2012. Subsidence is a form of coastal erosion that particularly affects river deltas. Deltas commonly subside as a result of the combined effects of rising sea level, compaction of delta sediments and lack of new inputs of terrestrial sediment because of dams upstream on the rivers flowing to the delta, and loss of delta vegetation because of changes that vary from coastal marsh plants killed by increasing salinization to coastal mangroves harvested for timber or cleared for aquaculture. Syvitski, et al. 2009 discusses the global scope of the problem of delta subsidence. Alongi 2008 discusses the beneficial effects of mangroves and the current rates of mangrove loss because of deforestation and other land uses. Salinization is another natural hazard in coastal regions. Salinization can result from excessive pumping of inland ground water, which reduces subsurface water pressure created by the freshwater aquifer, allowing saline ground water to move toward the land. Salinization can also result from decreased river flows as a result of consumptive water use upstream along the river network. In extreme cases, the river may no longer flow to the ocean and any dissolved material can precipitate on the delta as the limited surface water evaporates. Finally, irrigated agriculture in deltas located in drier climatic regions can result in precipitation of salts in delta sediments. Cardona, et al. 2004 discusses multiple causes of salinization of a coastal aquifer in Mexico. Rising sea level and more intense cyclonic storms associated with warming climate can also create coastal hazards in the form of storm surges and river tidal bores. Low-lying, densely populated countries such as Bangladesh can be particularly vulnerable to storm surges, as discussed in Karim and Mimura 2008. Lynch 1982 reviews characteristics of tidal bores, and Chanson 2011 updates this review and provides a more mechanistic understanding of the phenomenon of tidal bores. All of these natural hazards are of increasing concern because a large proportion of the global population is within one hundred kilometers of a coastline, and sea level is rising.

  • Alongi, D. M. 2008. Mangrove forests: Resilience, protection from tsunamis, and responses to global climate change. Estuarine, Coastal and Shelf Science 76:1–13.

    DOI: 10.1016/j.ecss.2007.08.024Save Citation »Export Citation »E-mail Citation »

    Mangrove forests are resilient to changing sea level, with relatively rapid rates of soil accretion and plant growth; mangroves provide numerous ecosystem services, including buffering the erosional energy associated with storm surges, hurricanes, and tsunamis, but average annual rates of 1–2 percent deforestation are severely reducing mangrove forests.

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  • Cardona, A., J. J. Carrillo-Rivera, R. Huizar-Alvarez, and E. Graniel-Castro. 2004. Salinization in coastal aquifers of arid zones: An example from Santo Domingo, Baja California Sur, Mexico. Environmental Geology 45:350–366.

    DOI: 10.1007/s00254-003-0874-2Save Citation »Export Citation »E-mail Citation »

    Causes of salinization in this coastal aquifer include infiltration from irrigated agricultural runoff enriched in salts and pumping of fresh ground water at rates faster than natural recharge; mitigation measures need to include regulations on where ground water wells are installed and how fast water is pumped.

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  • Chanson, H. 2011. Current knowledge in tidal bores and their environmental, ecological and cultural impacts. Environmental Fluid Mechanics 11:77–98.

    DOI: 10.1007/s10652-009-9160-5Save Citation »Export Citation »E-mail Citation »

    Thorough overview of the mechanics and occurrence of tidal bores and their effects, including increased suspension of fine sediments and nutrients, which can create feeding opportunities for aquatic animals, and hazards associated with river bank erosion and drownings.

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  • Karim, M. F., and N. Mimura. 2008. Impacts of climate change and sea-level rise on cyclonic storm surge floods in Bangladesh. Global Environmental Change 18:490–500.

    DOI: 10.1016/j.gloenvcha.2008.05.002Save Citation »Export Citation »E-mail Citation »

    Low-lying, densely populated Bangladesh is especially vulnerable to storm surges; this paper explores how increasing sea surface temperatures and rising sea level are enhancing the magnitude of cyclonic storm surge flooding in western Bangladesh.

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  • Lynch, D. K. 1982. Tidal bores. Scientific American, October: 146–156.

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    Comprehensive and accessible overview of the causes, mechanics, and effects of river tidal bores; bores form on rivers emptying into the ocean when the incoming tide creates a wave that moves up the river; hazards associated with bores include exacerbated erosion of the river bed and banks, shipwrecks, and drowning.

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  • Mars, J. C., and D. W. Houseknecht. 2007. Quantitative remote sensing study indicates doubling of coastal erosion rate in past 50 yr along a segment of the Arctic coast of Alaska. Geology 35:583–586.

    DOI: 10.1130/G23672A.1Save Citation »Export Citation »E-mail Citation »

    Reduced seasonal duration of sea ice has increased wave erosion and melting of permafrost in coastal sediments has made coast lines more vulnerable to erosion; increased rates of coastal erosion in the Arctic have caused breaching of thermokarst lakes and associated flooding that further exacerbate erosion.

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  • Pilkey, O. H. 2012. A time to look back at beach replenishment. Journal of Coastal Research 6:3–7.

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    A critical review of efforts to reduce coastal erosion by artificially depositing beach sand along areas vulnerable to erosion or areas popular for beach recreation; author notes poor record of predicting the durability of artificial beaches and failure to monitor effects of beach replenishment projects.

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  • Syvitski, J. P. M., A. J. Kettner, I. Overeem, et al. 2009. Sinking deltas due to human activities. Nature Geoscience 2:681–686.

    DOI: 10.1038/ngeo629Save Citation »Export Citation »E-mail Citation »

    Global overview of delta subsidence resulting from sediment compaction caused by removal of ground water, oil, and gas, along with sediment depletion because of upstream reservoirs; 85 percent of thirty-three deltas assessed experienced severe flooding within the previous decade; authors estimate that delta surface vulnerable to flooding could increase by 50 percent during the next century.

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Atmospheric scientists and meteorologists investigate the geographic occurrence, storm mechanics, and prediction and warning of hazards associated with cyclones. Environmental geologists investigate secondary hazards caused by cyclones, such as storm surges, inland flooding, hillslope failures, and delta and coastal erosion. The works cited in this section include examples of diverse forms of secondary geological hazards caused by cyclones, which are also known as hurricanes in North America. Day, et al. 2007 discusses restoration of the Mississippi River delta after two large hurricanes during the early 21st century. Dethier, et al. 2016 reviews the role of cyclone-induced landslides that introduce sediment and large wood to stream channels, accelerating rates of landscape evolution in tectonically stable regions such as New England, United States. Massive blowdown of trees is invoked in Phillips and Park 2009 as a potential explanation for the extensive wood rafts historically present on rivers in the southeastern United States. Emanuel 2005 develops an index of cyclone destructiveness and documents how cyclones have become increasingly destructive during recent decades. Woodruff, et al. 2013 describes how rising sea level during the early Holocene epoch of geological time provides an analogue for understanding projected greater coastal flooding during cyclones under contemporary rising sea levels. Nott 2004 discusses diverse lines of evidence that can be used to infer the magnitude and chronology of prehistoric cyclones. Senkbeil, et al. 2012 reviews the reasons that cyclone-related hazards are likely to increase in the near future along coastal regions of the United States. Many of the reasons discussed in this article apply to other coastal areas of the world that experience cyclones. Stone, et al. 2004 provides an example of why it is so difficult to predict the exact response of coastal features to increased cyclone activity, discussing the interactions of various types of storms with barrier islands along the southeastern United States.

  • Day, J. W., D. F. Boesch, E. J. Clairain, et al. 2007. Restoration of the Mississippi Delta: Lessons from Hurricanes Katrina and Rita. Science 316:1679–1684.

    DOI: 10.1126/science.1137030Save Citation »Export Citation »E-mail Citation »

    Explains how knowledge of the history of geologic evolution of the delta during the past few thousand years is necessary to understand how human modifications have exacerbated vulnerability of the Mississippi River delta to erosion during hurricanes.

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  • Dethier, E., F. J. Magilligan, C. E. Renshaw, and K. H. Nislow. 2016. The role of chronic and episodic disturbances on channel-hillslope coupling: The persistence and legacy of extreme floods. Earth Surface Processes and Landforms 41:1437–1447.

    DOI: 10.1002/esp.3958Save Citation »Export Citation »E-mail Citation »

    Used aerial photographs and sediment records to assess stream and hillslope response to a tropical storm that affected New England in the United States; among the major effects of the storm were numerous landslides that introduced massive quantities of sediment and large wood to stream channels.

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  • Emanuel, K. 2005. Increasing destructiveness of tropical cyclones over the past 30 years. Nature 436:686–688.

    DOI: 10.1038/nature03906Save Citation »Export Citation »E-mail Citation »

    Defines an index of potential cyclone destructiveness based on total dissipation of power, integrated over the duration of the cyclone; this index has increased markedly since the mid-1970s as a result of longer storms and greater storm intensities; net storm power dissipation correlates with tropical sea surface temperature rises associated with global warming.

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  • Nott, J. 2004. Palaeotempestology: The study of prehistoric tropical cyclones—a review and implications for hazard assessment. Environment International 30:433–447.

    DOI: 10.1016/j.envint.2003.09.010Save Citation »Export Citation »E-mail Citation »

    Records of prehistoric cyclones include coastal ridges of coral rubble, sand, and shells; erosional terraces in raised gravel beaches, barrier wash-over deposits, and sediment deposits in shallow offshore areas. These records extend back at least 5,500 years and indicate fluctuations in magnitude and frequency of cyclones.

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  • Phillips, J. D., and L. Park. 2009. Forest blowdown impacts of Hurricane Rita on fluvial systems. Earth Surface Processes and Landforms 34:1069–1081.

    DOI: 10.1002/esp.1793Save Citation »Export Citation »E-mail Citation »

    Uses an example of a recent hurricane to investigate how strong winds can cause extensive forest damage and blow hundreds to thousands of trees into river channels; speculates that such massive blowdowns might help to explain the extensive rafts of downed trees historically present on rivers of the southeastern United States.

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  • Senkbeil, J. C., D. M. Brommer, and I. J. Comstock. 2012. Tropical cyclone hazards in the USA. Geography Compass 5:544–563.

    DOI: 10.1111/j.1749-8198.2011.00439.xSave Citation »Export Citation »E-mail Citation »

    Review of the current state of hurricane hazards in the United States, where coastal development, increasing population density, and increasing hurricane activity are likely to cause greater cyclone-related hazards in the near future; includes discussion of water and wind hazards with cyclones, as well as social factors such as hazard perception.

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  • Stone, G. W., B. Liu, G. A. Pepper, and P. Wang. 2004. The importance of extratropical and tropical cyclones on the short-term evolution of barrier islands along the northern Gulf of Mexico, USA. Marine Geology 210:63–78.

    DOI: 10.1016/j.margeo.2004.05.021Save Citation »Export Citation »E-mail Citation »

    Documents the complex interactions among sediment supply and the temporal sequence of different types of storms in creating and maintaining barrier islands along a portion of the Florida coast, as well as how changes in storm intensity and frequency might affect these islands.

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  • Woodruff, J. D., J. L. Irish, and S. J. Camargo. 2013. Coastal flooding by tropical cyclones and sea-level rise. Nature 504:44–52.

    DOI: 10.1038/nature12855Save Citation »Export Citation »E-mail Citation »

    Rising sea level will increase flooding associated with tropical cyclones; potential changes can be compared to an analogous episode of rapid sea level rise during the early Holocene epoch, when most low-lying coastlines were much less resilient to storm impacts.

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Environmental geologists investigate the geographic occurrence of earthquakes, including the underlying geologic controls, as discussed for the Puget Sound region in Hyndman, et al. 2003; for the San Andreas Fault in Bakun, et al. 2005; and for all of Italy in Basili, et al. 2008. Environmental geologists also investigate how human activities such as hydraulic fracturing can trigger earthquakes and exacerbate earthquake hazards in regions not normally subject to seismic activity. Ellsworth 2013 reviews knowledge of injection-induced earthquakes. Environmental geologists use diverse lines of evidence to infer the magnitude and chronology of prehistoric earthquakes. Strasser, et al. 2006 uses landslide deposits in lakes to infer prehistoric earthquakes in Switzerland, and Thomas, et al. 2005 uses liquefaction features in sand deposits to date prehistoric earthquakes in Assam, India. Environmental geology can involve investigation of the location, magnitude, and chronology of secondary hazards triggered by seismic shaking, such as the rockslides described in Sepulveda, et al. 2005. Finally, environmental geologists are involved in earthquake prediction and warning. Weldon, et al. 2005 discusses how geological ruptures can be used to infer characteristics of past large earthquakes and predict future earthquake scenarios along the San Andreas Fault of California.

  • Bakun, W. H., B. Aagaard, B. Dost, et al. 2005. Implications for prediction and hazard assessment from the 2004 Parkfield earthquake. Nature 437:969–974.

    DOI: 10.1038/nature04067Save Citation »Export Citation »E-mail Citation »

    A 2004 earthquake along the highly instrumented San Andreas Fault in California provided new insights into earthquake physics; of particular importance, the 2004 earthquake, which lacked obvious precursors, indicated the difficulty of making reliable, short-term earthquake predictions; the authors suggest focusing predictions on the strength and location of damaging ground shaking.

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  • Basili, R., G. Valensise, P. Vannoli, et al. 2008. The Database of Individual Seismogenic Sources (DISS), Version 3: Summarizing 20 years of research on Italy’s earthquake geology. Tectonophysics 453:20–43.

    DOI: 10.1016/j.tecto.2007.04.014Save Citation »Export Citation »E-mail Citation »

    An example of how multiyear databases of earthquake occurrence can be used to understand geologic controls on earthquake location and intensity; the database includes measurements of stress and strain data available from boreholes and GPS measurements that can be used to investigate relationships between faults at the surface and at depth.

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  • Ellsworth, W. L. 2013. Injection-induced earthquakes. Science 341:1–8.

    DOI: 10.1126/science.1225942Save Citation »Export Citation »E-mail Citation »

    Earthquakes in areas not known for seismic activity have occurred in North America and Europe in connection with injection of fluids into underground rock formations; this is particularly well documented where hydraulic fracturing is used to obtain oil and gas from tight shale formations; reviews recent earthquakes associated with injection and scientific challenges to assessing this hazard.

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  • Hyndman, R. D., S. Mazzotti, D. Weichert, and G. C. Rogers. 2003. Frequency of large crustal earthquakes in Puget Sound–Southern Georgia Strait predicted from geodetic and geological deformation rates. Journal of Geophysical Research Solid Earth 108.

    DOI: 10.1029/2001JB001710Save Citation »Export Citation »E-mail Citation »

    Inferred frequency of large earthquakes is mainly based on extrapolation of the statistics of smaller earthquakes from the short instrumental record; this article obtains an independent estimate derived from current rates of crustal deformation indicated by GPS and geological data, which suggests a long-term occurrence of large earthquakes double the current rate.

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  • Sepulveda, S. A., W. Murphy, and D. N. Petley. 2005. Topographic controls on coseismic rock slides during the 1999 Chi-Chi earthquake, Taiwan. Quarterly Journal of Engineering Geology and Hydrogeology 38:189–196.

    DOI: 10.1144/1470-9236/04-062Save Citation »Export Citation »E-mail Citation »

    Examines how a large earthquake in 1999 interacted with site-specific geologic characteristics to trigger massive rockslides in Taiwan; hillslope orientation and height, along with wavelength of seismic waves, appear to strongly influence the amplification of ground motions and the occurrence of rockslides.

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  • Strasser, M., F. S. Anselmetti, D. Fah, D. Giardini, and M. Schnellmann. 2006. Magnitudes and source areas of large prehistoric northern Alpine earthquakes revealed by slope failures in lakes. Geology 34:1005–1008.

    DOI: 10.1130/G22784A.1Save Citation »Export Citation »E-mail Citation »

    Used seismic surveys and sediment cores to characterize subaqueous landslide sediments in Lake Zurich and Lake Lucerne of Switzerland; sediments indicate the potential for earthquakes and large landslides in heavily populated regions that have not experienced earthquakes during historic time.

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  • Thomas, P. J., D. V. Reddy, D. Kumar, P. Nagabhushanam, B. S. Sukhija, and R. N. Sahoo. 2005. Optical dating of liquefaction features to constrain prehistoric earthquakes in Upper Assam, NE India—some preliminary results. Quaternary Geochronology 2:278–283.

    DOI: 10.1016/j.quageo.2006.03.013Save Citation »Export Citation »E-mail Citation »

    Seismic shaking can cause sediment to become liquefied, which leaves characteristic sedimentary deposits; uses geochronology to determine the age of liquefied sand structures and constrain the timing of prehistoric earthquakes in Upper Assam to between 1430 and 1630 CE.

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  • Weldon, R. J., T. E. Fumal, G. P. Biasi, and K. M. Scharer. 2005. Past and future earthquakes on the San Andreas Fault. Science 308:966–967.

    DOI: 10.1126/science.1111707Save Citation »Export Citation »E-mail Citation »

    Uses the date and ground displacement at isolated sites along ruptures hundreds of kilometers long to develop rupture scenarios, which are possible histories of earthquakes that include the date, location, and length of fault rupture of all earthquakes on a fault during a period of time.

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Extraterrestrial Impacts

Planetary geologists and astronomers are more likely than environmental geologists to investigate the celestial mechanics of extraterrestrial objects and to predict when such objects might intersect Earth’s orbit. Paleontologists and evolutionary biologists focus on the effects of an extraterrestrial impact on organisms and ecosystems, as illustrated in Spezzaferri, et al. 2002. Environmental geologists tend to focus on geologic evidence of the occurrence of extraterrestrial impacts, including the chronology of such impacts and the secondary effects. The works cited in this section include those that describe specific geological evidence of extraterrestrial impacts, such as Jourdan, et al. 2011, which uses argon dating of an impact crater; Abbott, et al. 2012, which uses elemental profiles in zircon crystals; and Stankowski 2011, which uses multiple techniques to date spherule-rich sediment layers. Rasmussen and Koeberl 2004 uses elemental anomalies and the presence of shocked quartz in rocks from an ancient, geologically stable portion of Australia to infer ancient extraterrestrial impacts. Uysal, et al. 2001 discusses the use of K-Ar dating of impact-induced clays to determine the age of recently discovered large impact crater in Australia. Multiple works discuss geological evidence from Australia because that continent has been tectonically stable for a much longer period of time than most of the other continents, thus preserving ancient rocks with a longer record of extraterrestrial impacts. Simonson and Glass 2004 describes the formation of natural glass spherules as a result of extraterrestrial impacts. Baillie 2007 notes the existing evidence for extraterrestrial impacts and their environmental effects, and questions why more effort is not given to searching for such evidence in cores of glacial ice and sediment from diverse depositional environments.

  • Abbott, S. S., T. M. Harrison, A. K. Schmitt, and S. J. Mojzsis. 2012. A search for thermal excursions from ancient extraterrestrial impacts using Hadean zircon Ti-U-Th-Pb depth profiles. Proceedings of the National Academy of Sciences of the United States of America 109:13,486–13,492.

    DOI: 10.1073/pnas.1208006109Save Citation »Export Citation »E-mail Citation »

    Discusses uniquely long-term records of geologic history in the form of zircons from a region of Western Australia; these zircons include outer crystal layers that record age and temperature of crystallization and suggest extraterrestrial impacts during a spike of bombardment to the inner solar system c. 3.85–3.95 billion years ago.

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  • Baillie, M. 2007. The case for significant numbers of extraterrestrial impacts through the late Holocene. Journal of Quaternary Science 22:101–109.

    DOI: 10.1002/jqs.1099Save Citation »Export Citation »E-mail Citation »

    Questions why more research is not targeting the evidence of extraterrestrial impacts and their environmental effects; suggests that more attention should be paid to indicators such as shocked minerals and ejecta when examining cores of glacial ice and sediments from marine, peat, and lake environments.

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  • Jourdan, F., F. Moynier, C. Koeberl, and S. Eroglu. 2011. 40Ar/39Ar age of the Lonar crater and consequence for the geochronology of planetary impacts. Geology 39:671–674.

    DOI: 10.1130/G31888.1Save Citation »Export Citation »E-mail Citation »

    The Lonar crater in India occurs in basalt and thus provides a good proxy for extraterrestrial impacts to other planets; authors use Ar–Ar dating to estimate an age of 570,000 years and demonstrate why basaltic rocks melted by extraterrestrial impacts provide more accurate ages for the impact events than provided by other types of rocks.

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  • Rasmussen, B., and C. Koeberl. 2004. Iridium anomalies and shocked quartz in a Late Archean spherule layer from the Pilbara craton: New evidence for a major asteroid impact at 2.63 Ga. Geology 32:1029–1032.

    DOI: 10.1130/G20825.1Save Citation »Export Citation »E-mail Citation »

    Uses multiple geologic indicators, including enriched iridium, shocked quartz minerals, and spherule layers of natural glass, to infer an extraterrestrial impact at a continental site during the Precambrian Era of geologic time; the ejecta blanket covers an area greater than thirty-two thousand square kilometers.

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  • Simonson, B. M., and B. P. Glass. 2004. Spherule layers—records of ancient impacts. Annual Reviews of Earth and Planetary Sciences 32:329–361.

    DOI: 10.1146/annurev.earth.32.101802.120458Save Citation »Export Citation »E-mail Citation »

    The enormous velocity of extraterrestrial objects striking Earth can melt and vaporize silicate minerals, which condense into spheroidal, sand-sized particles that can be deposited thousands of kilometers away from the impact site; these impact spherules of natural glass are abundant in a few discrete layers ranging from less than a million to 3.47 billion years in age.

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  • Spezzaferri, S., D. Basso, and R. Coccioni. 2002. Late Eocene planktonic foraminiferal response to an extraterrestrial impact at Massignano GSSP (northeastern Apennines, Italy). Journal of Foraminiferal Research 32:188–199.

    DOI: 10.2113/0320188Save Citation »Export Citation »E-mail Citation »

    Investigated fossils of planktonic foraminifera from sediments deposited around the time of an extraterrestrial impact dated at 35.7 million years ago; associated climatic cooling changed water mass structure and temperature profiles, causing declines in shallow- and warm-water foram species, and a feedback mechanism sustained the initial impact-induced changes.

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  • Stankowski, W. T. J. 2011. Luminescence and radiocarbon dating as tools for the recognition of extraterrestrial impacts. Geochronometria 38:50–54.

    DOI: 10.2478/s13386-011-0004-ySave Citation »Export Citation »E-mail Citation »

    Example of using multiple geochronologic techniques to determine the ages of sediment layers containing impact-generated spherules.

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  • Uysal, I. T., S. D. Golding, A. Y. Glikson, A. J. Mory, and M. Glikson. 2001. K-Ar evidence from illitic clays of a Late Devonian age for the 120 km diameter Woodleigh impact structure, Southern Carnarvon Basin, Western Australia. Earth and Planetary Science Letters 192:281–289.

    DOI: 10.1016/S0012-821X(01)00450-2Save Citation »Export Citation »E-mail Citation »

    Uses K–Ar dating of clays interpreted to be impact-induced hydrothermal alteration products to determine the age of a recently discovered large impact structure in Western Australia; structure is approximately 359 million years old, which suggests that environmental effects from the impact may have contributed to a widespread extinctions during the late Devonian period of geologic time.

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Environmental geologists investigate many aspects of floods, including geographic occurrence; geologic controls on flood magnitude and duration; human activities that exacerbate the occurrence of flooding and the hazards resulting from flooding; the magnitude and frequency of prehistoric floods, which can be used to predict future flood magnitude; and flood warning systems. O’Connor, et al. 2002 discusses the geographic occurrence of floods, including physical limits on the largest rainfall-generated floods. Hirschboeck 1987 correlates the occurrence of decadal fluctuations in flash floods across the continental United States during the 20th century with fluctuations in the strength and zonality of the jet stream. One of the most distinctive contributions of environmental geology to the understanding of flood occurrence and flood hazards is the use of diverse geologic records to infer the timing and magnitude of prehistoric floods. Prehistoric floods, which are commonly considered to include any flood not directly measured by stream gages, are also known as paleofloods. Some of the earliest, qualitative work on paleofloods began during the mid-20th century, but V. R. Baker largely founded quantitative study of paleofloods during the early 1970s. Baker 2008 provides a review of the development of paleofloods studies and discusses potential future directions for the discipline. Cenderelli and Wohl 2003 discusses quantitative reconstruction of two recent but ungaged glacial-lake outburst floods in Nepal, and Ely, et al. 2005 provides a regional synthesis of numerous paleofloods records for the southwestern United States. Harden, et al. 2010 extends this regional synthesis by combining two different types of prehistoric sedimentary records of floods. Similarly, Macklin and Lewin 2003 synthesizes prehistoric flood records from across Britain and documents fourteen major episodes of flooding during the past ten thousand years. Wohl 2000 is an edited collection that addresses most aspects of environmental geology associated with floods, from the benefits floods create for river ecosystems to the hazards that that floods create for human communities and infrastructure.

  • Baker, V. R. 2008. Paleoflood hydrology: Origin, progress, prospects. Geomorphology 101:1–13.

    DOI: 10.1016/j.geomorph.2008.05.016Save Citation »Export Citation »E-mail Citation »

    Paleoflood hydrology emerged during the 1970s and 1980s with the development of hydraulic modeling of individual paleofloods using flood erosional and depositional features; advances in hydraulic modeling, geochronology, and statistical analysis of mixed systematic and geological records of floods allowed development of paleofloods records from diverse regions that can now be combined for global-scale syntheses.

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  • Cenderelli, D. A., and E. E. Wohl. 2003. Flow hydraulics and geomorphic effects of glacial-lake outburst floods in the Mount Everest region, Nepal. Earth Surface Processes and Landforms 28:385–407.

    DOI: 10.1002/esp.448Save Citation »Export Citation »E-mail Citation »

    Example of using erosional and depositional features to model the hydraulics of two recent but ungaged glacial-lake outburst floods in Nepal; these floods were up to sixty times larger than normal, snowmelt floods in the region, a scenario which is not uncommon for outburst floods.

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  • Ely, L. L., Y. Enzel, V. R. Baker, and D. R. Cayan. 2005. A 5000-year record of extreme floods and climate change in the southwestern United States. Science 262:410–412.

    DOI: 10.1126/science.262.5132.410Save Citation »Export Citation »E-mail Citation »

    Example of a regional paleoflood record that draws on studies from multiple sites in the southwestern United States to infer periods of frequent flooding associated with El Nino climate events c. 4,800 to 3,600 years ago; 1,000 years ago; and within the last 500 years.

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  • Harden, T., M. G. Macklin, and V. R. Baker. 2010. Holocene flood histories in south-western USA. Earth Surface Processes and Landforms 35:707–716.

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    Combines two sources of information on prehistoric hydrologic conditions, paleoflood records and cycles of cutting and filling of alluvial channels in the southwestern United States; resulting probability-based flood record includes seven episodes of increasing flooding that coincide with increased precipitation and lower temperatures during the past eleven thousand years.

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  • Hirschboeck, K. K. 1987. Catastrophic flooding and atmospheric circulation anomalies. In Catastrophic flooding. Edited by L. Mayer and D. Nash, 23–56. Boston: Allen and Unwin.

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    Ties multi-decadal periods of enhanced flash floods across the continental United States to periods of more meridional atmospheric circulation, and periods of reduced flash floods to periods of more zonal atmospheric circulation.

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  • Macklin, M. G., and J. Lewin. 2003. River sediments, great floods, centennial-scale Holocene climate change. Journal of Quaternary Science 18:101–105.

    DOI: 10.1002/jqs.751Save Citation »Export Citation »E-mail Citation »

    Synthesizes flood sedimentary records and associated radiocarbon ages of floods from more than three hundred sediment units across Britain to evaluate sensitivity of flooding to climate variations; rivers are sensitive to relatively modest climate changes, with fourteen major episodes of flooding during the last ten thousand years.

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  • O’Connor, J. E., G. E. Grant, and J. E. Costa. 2002. The geology and geography of floods. In Ancient floods, modern hazards: Principles and applications of paleoflood hydrology. Edited by P. K. House, R. H. Webb, V. R. Baker, and D. R. Levish, 359–385. Washington, DC: American Geophysical Union.

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    Reviews the geographical occurrence of different types of floods and the physical limits on flood size; high-relief topography is particularly effective in promoting precipitation-induced floods; also discusses floods from natural and artificial dam failures.

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  • Wohl, E., ed. 2000. Inland flood hazards: Human, riparian, and aquatic communities. Cambridge, UK: Cambridge Univ. Press.

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    Edited volume of nineteen chapters that cover controls on flooding, human effects on flood hazards, flood processes and effects, effects of floods on human communities, and flood hazard mitigation strategies; includes consideration of beneficial effects of floods on aquatic and riparian ecosystems.

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Hillslope Instability

As with other natural hazards, environmental geology focuses on the geographic distribution of unstable hillslopes, along with geologic controls and human exacerbation of processes that create instability. Ho, et al. 2012 provides an example, with a focus on the effects of soil thickness on landslide occurrence. Meunier, et al. 2008 investigates the effect of topography on landslides induced by seismic waves and by precipitation. Unstable hillslopes can fail via gradual processes such as creep and heave, but the most severe hazards typically occur in association with abrupt failures such as debris flows and landslides. Environmental geologists document the magnitude and frequency of both contemporary and prehistoric hillslope failures, as illustrated in Karlin, et al. 2004, which develops a record of prehistoric landslides triggered by earthquakes, as recorded in lake sediments. Panek, et al. 2010 uses multiple paleoclimatic indicators and geochronologic techniques to reconstruct the history of movement on a particularly large landslide. Korup 2005 assesses the role of large landslides in delivering sediment to lower elevations and to river networks. Larsen, et al. 2010 calibrates volume-area relationships for soil and bedrock landslides and relates rates of landslide erosion to rates of rock uplift. Environmental geologists also assess landslide hazards, as reviewed in van Westen, et al. 2006, and work to develop methods for predicting and mitigating hazards of hillslope failures. Wilkinson, et al. 2002 develops a numerical model that can be used in the context of slope stabilization.

  • Ho, J. -Y., K. T. Lee, T.-C. Chang, Z. Y. Wang, and Y. H. Liao. 2012. Influences of spatial distribution of soil thickness on shallow landslide prediction. Engineering Geology 124:38–46.

    DOI: 10.1016/j.enggeo.2011.09.013Save Citation »Export Citation »E-mail Citation »

    Soil thickness influences slope stability, but information on the spatial distribution of soil thickness is seldom assessed; this case study from Taiwan indicates that soil thickness and wetness index provide accurate indicators of slope stability and are relatively easy to obtain.

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  • Karlin, R. E., M. Holmes, S. E. B. Abella, and R. Sylwester. 2004. Holocene landslides and a 3500-year record of Pacific Northwest earthquakes from sediments in Lake Washington. Geological Society of America Bulletin 116:94–108.

    DOI: 10.1130/B25158.1Save Citation »Export Citation »E-mail Citation »

    Shallow geophysical imaging and sediment cores from a lake reveal prehistoric submarine landslides triggered by earthquakes; radiocarbon dating indicates seven landslides during the past 3,500 years, which constrains the recurrence interval for earthquakes.

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  • Korup, O. 2005. Large landslides and their effect on sediment flux in South Westland, New Zealand. Earth Surface Processes and Landforms 30:305–323.

    DOI: 10.1002/esp.1143Save Citation »Export Citation »E-mail Citation »

    Used remote imagery to map large landslides in New Zealand; investigates interactions of landslides with rivers as well as the magnitude and persistence of sediment delivered by landslides.

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  • Larsen, I. J., D. R. Montgomery, and O. Korup. 2010. Landslide erosion controlled by hillslope material. Nature Geoscience 3:247–251.

    DOI: 10.1038/ngeo776Save Citation »Export Citation »E-mail Citation »

    Compiles landslide geometry measurements from more than four thousand landslides to assess the relative volume-area scaling relationships for bedrock and soil landslides; infers that landslides can erode steep hillslopes at rates commensurate with even rapid tectonic uplift.

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  • Meunier, P., N. Hovius, and J. A. Haines. 2008. Topographic site effects and the location of earthquake-induced landslides. Earth and Planetary Science Letters 275:221–232.

    DOI: 10.1016/j.epsl.2008.07.020Save Citation »Export Citation »E-mail Citation »

    Seismic shaking propagates in a manner partly influenced by topography; earthquake-triggered landslides cluster near ridge crests, whereas rainfall-triggered landslides are evenly distributed over hillslopes; consequently, knowledge of the effects of topography on attenuation of seismic waves can be useful in predicting spatial patterns of earthquake-induced landslides.

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  • Panek, T., J. Hradecky, V. Smolkova, K. Silhan, J. Minar, and V. Zerntiskaya. 2010. The largest prehistoric landslide in northwestern Slovakia: Chronological constraints of the Kykula long-runout landslide and related dammed lakes. Geomorphology 120:233–247.

    DOI: 10.1016/j.geomorph.2010.03.033Save Citation »Export Citation »E-mail Citation »

    Uses radiocarbon dating, pollen analysis, and sedimentology of landslide-dammed lakes and colluvial peat bogs to reconstruct changes in climate and surface processes at the largest prehistoric landslide in the northwestern Carpathian Mountains, where the primary landslide movement occurred during the transition from late glacial to Holocene conditions.

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  • van Westen, C. J., T. W. J. van Asch, and R. Soeters. 2006. Landslide hazard and risk zonation—why is it still so difficult? Bulletin of Engineering Geology and the Environment 65:167–184.

    DOI: 10.1007/s10064-005-0023-0Save Citation »Export Citation »E-mail Citation »

    Although quantitative risk assessment is feasible on a site-investigation scale, the generation of quantitative risk zonation maps for regulatory planning by local authorities remains problematic because of difficulties in quantifying landslide risk over large areas; provides useful overview of different approaches to landslide hazard and risk zonation.

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  • Wilkinson, P. L., M. G. Anderson, and D. M. Lloyd. 2002. An integrated hydrological model for rain-induced landslide prediction. Earth Surface Processes and Landforms 27:1285–1297.

    DOI: 10.1002/esp.409Save Citation »Export Citation »E-mail Citation »

    Uses a physically based numerical model that includes the effects of vegetation, slope topography, and saturated and unsaturated zone hydrologic conditions to assess slope stability; sample applications to sites in New Zealand and Hong Kong illustrate application of the model in the context of slope stabilization and hazard mitigation.

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Karst refers to both processes and landforms. Karst processes involve the dissolution of calcium carbonate rocks, such as limestone and dolomite, under surface or near-surface conditions. Karst landforms are the surface and subsurface features that result from this dissolution, most notably caves in the subsurface. In the context of natural hazards, karst becomes important with respect to ground water dynamics and collapse of the surface into underlying cavities, a process that creates sinkholes. The large subsurface conduits that can develop in karst terrains can also promote unusual floods and landslide failures, as reviewed in Gutierrez, et al. 2014. Environmental geology involves mapping the surface and subsurface location of carbonate bedrock, as well as the characteristics of the bedrock that influence the rate and magnitude of karst dissolution, including joints, bedding planes, and porosity and permeability of the rock, and fluctuations of the water table and ground water transmission rates that influence karst dissolution. Delle Rose and Parise 2002 provides an example of a regional overview of the conditions leading to karst dissolution and surface collapse features. Environmental geologists work to predict locations subject to karst collapse and to understand how human alteration of the hydrologic cycle can enhance karst dissolution, as in the case of the urbanization described in Simon, et al. 2008. In the context of groundwater resources, karst becomes important because karst aquifers in a natural state commonly have exceptionally pure water, but pollutants introduced from surface or subsurface sources can move rapidly through a karst aquifer and produce persistent contamination, as illustrated in Liu, et al. 2006. Bakalowicz 2005 discusses the complexities of karst aquifers, including the difficulty nonlinearities and threshold effects associated with flow in a medium that combines conduits and a porous matrix. Goldscheider 2005 presents a method to assess the vulnerability of karst aquifers. Hancock, et al. 2005 reviews the limited existing knowledge of groundwater ecosystems and the interactions between subsurface biota and water quality. Loaiciga, et al. 2000 provides a case study of modeling future conditions in a karst aquifer vulnerable to decreased recharge associated with a warming climate.

  • Bakalowicz, M. 2005. Karst groundwater: A challenge for new resources. Hydrogeology Journal 13:148–160.

    DOI: 10.1007/s10040-004-0402-9Save Citation »Export Citation »E-mail Citation »

    Useful overview of the characteristics of karst aquifers, including an explanation of why the field and modeling approaches commonly used in groundwater geology do not necessarily work well for karst aquifers.

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  • delle Rose, M., and M. Parise. 2002. Karst subsidence in south-central Apulia, southern Italy. International Journal of Speleology 31:181–199.

    DOI: 10.5038/1827-806X.31.1.11Save Citation »Export Citation »E-mail Citation »

    Nice regional case study that describes inland subsidence in the form of individual cavities and coastal subsidence composed of compound sinks that extend across thousands of square meters; discusses some of the engineering hazards associated with surface subsidence following subsurface dissolution, and explains the geological and hydrological influences on dissolution landforms.

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  • Goldscheider, N. 2005. Karst groundwater vulnerability mapping: Application of a new method in the Swabian Alb, Germany. Hydrogeology Journal 13:555–564.

    DOI: 10.1007/s10040-003-0291-3Save Citation »Export Citation »E-mail Citation »

    Discusses mapping the vulnerability of ground water in karst aquifers based on the presence of protective cover and infiltration conditions and provides a case study of using the method to assess groundwater in southern Germany.

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  • Gutierrez, F., M. Parise, J. De Waele, and H. Jourde. 2014. A review on natural and human-induced geohazards and impacts in karst. Earth-Science Reviews 138:61–88.

    DOI: 10.1016/j.earscirev.2014.08.002Save Citation »Export Citation »E-mail Citation »

    Thorough review of the characteristics that make karst environments both potentially hazardous to human communities and vulnerable to groundwater pollution from human activities; focuses on hazards associated with sinkholes, floods, and landslides.

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  • Hancock, P. J., A. J. Boulton, and W. F. Humphreys. 2005. Aquifers and hyporheic zones: Towards an ecological understanding of groundwater. Hydrogeology Journal 13:98–111.

    DOI: 10.1007/s10040-004-0421-6Save Citation »Export Citation »E-mail Citation »

    Although not unique to karst aquifers, the distinctive biotic communities within aquifers, such as microbial biofilms, can be important in maintaining ground and surface water quality; changes in the populations of subsurface fauna that graze biofilms can reflect changes in water quality.

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  • Liu, C. Q., S. L. Li, Y. C. Lang, and H. Y. Xiao. 2006. Using δ15N- and δ18O-values to identify nitrate sources in karst ground water, Guiyang, Southwest China. Environmental Science and Technology 40:6928–6933.

    DOI: 10.1021/es0610129Save Citation »Export Citation »E-mail Citation »

    Case study involving identifying the sources of nitrate pollution in a karst aquifer in China; analysis of major ions in surface and groundwater samples during different times of the year indicates multiple sources of nitrate, including chemical fertilizer and sewage effluents.

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  • Loaiciga, H. A., D. R. Maidment, and J. B. Valdes. 2000. Climate-change impacts in a regional karst aquifer, Texas, USA. Journal of Hydrology 227:173–194.

    DOI: 10.1016/S0022-1694(99)00179-1Save Citation »Export Citation »E-mail Citation »

    Like other karst aquifers, the Edwards Aquifer in Texas is at risk from groundwater pumping and reduced recharge associated with climate change; this paper reports numerical modeling of future climate conditions that indicates future water shortages even in the absence of increased water withdrawals.

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  • Simon, J. L., M. A. Soriano, L. E. Arlegui, J. Gracia, C. L. Liesa, and A. Pocovi. 2008. Space-time distribution of ancient and active alluvial karst subsidence: Examples from the central Ebro Basin, Spain. Environmental Geology 53:1057–1065.

    DOI: 10.1007/s00254-007-0732-8Save Citation »Export Citation »E-mail Citation »

    Examines both contemporary and now-inactive karst subsidence features in order to determine whether subsidence rates have changed through time; finds that urbanization increased subsidence rates.

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Natural hazards associated with soils can take the form of subsidence, creep, and erosion. Subsidence and creep both occur in response to repeated small-scale displacements in soils associated with cycles of wetting and drying or freezing and thawing. When soil is repeatedly wetted and dried, some clay minerals absorb water and expand, then shrink as the soil dries. This expansion and contraction reduces interparticle cohesion and friction within the soil. Thomas, et al. 2000 illustrates how shrink-swell potential of a soil is assessed. Similarly, when soil is repeatedly frozen and thawed, the expansion of ice crystals forces soil particles apart and the particles do not pack as tightly together again when the ice melts. These repeated movements can force portions of the ground surface upward while other portions collapse, leading to subsidence that damages buildings and infrastructure, as thoroughly reviewed in Baum, et al. 2008. Reduction of soil cohesion and interparticle friction can also allow soil to move slowly down even very gentle slopes, a process known as creep. Creep can gradually deform structures on the surface, such as roads, and creep can be a precursor to more rapid downslope movements such as landslides. McKean, et al. 1993 illustrates some of the isotopic dating methods used to infer long-term rates of downslope creep. Some of the most rapid and substantial creep occurs in high-latitude regions where warming air temperatures are causing permafrost—permanently frozen soil—to thaw, as discussed in Harris, et al. 2001 for mountainous regions. Soil erosion creates hazards in the form of loss of soil fertility and excess sedimentation where eroded soils are deposited by wind or water. Montgomery 2007 provides an engaging and accessible overview of the history of soil erosion and problems created by this erosion. Morgan 2005 provides a more technical treatment of causes and mitigation of soil erosion. Prediction of soil erosion commonly starts with the Universal Soil Loss Equation (USLE), a method originally developed for agricultural lands in the United States. Haile and Fetene 2012 provides an example of applying USLE to estimating soil erosion in Ethiopia. Limitations of the USLE model led to development of RUSLE, the Revised Universal Soil Loss Equation, and Xu, et al. 2013 provides an example of applying this equation to a site in China.

  • Baum, R. L., D. L. Galloway, and E. Harp. 2008. Landslide and land subsidence hazards to pipelines. Open-File Report 1164. Reston, VA: US Geological Survey.

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    Land subsidence is a widespread problem that creates hazards for infrastructure such as pipelines and roads; comprehensive review of land subsidence hazards caused by withdrawal of subsurface fluids, mining, soil drainage, thawing permafrost, and shrink-swell soils.

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  • Haile, G. W., and M. Fetene. 2012. Assessment of soil erosion hazard in Kilie catchment, East Shoa, Ethiopia. Land Degradation and Development 23:293–306.

    DOI: 10.1002/ldr.1082Save Citation »Export Citation »E-mail Citation »

    Employs the commonly used USLE model, along with remote sensing, geographic information systems, and measurements of ground erosion features, to develop a risk map of soil erosion; representative case study of applying USLE to predicting soil erosion.

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  • Harris, C., M. C. R. Davies, and B. Etzelmuller. 2001. The assessment of potential geotechnical hazards associated with mountain permafrost in a warming global climate. Permafrost and Periglacial Processes 12:145–156.

    DOI: 10.1002/ppp.376Save Citation »Export Citation »E-mail Citation »

    Discusses evaluation of hazards associated with thawing of permafrost in mountainous regions of Europe, where permafrost is already close to zero Celsius and therefore particularly susceptible to alterations in thermal characteristics of the ground, as well as warming air temperatures.

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  • McKean, J. A., W. E. Dietrich, R. C. Finkel, J. R. Southon, and M. W. Caffee. 1993. Quantification of soil production and downslope creep rates from cosmogenic 10Be accumulations on a hillslope profile. Geology 21:343–346.

    DOI: 10.1130/0091-7613(1993)021<0343:QOSPAD>2.3.CO;2Save Citation »Export Citation »E-mail Citation »

    Uses measured soil concentrations of a cosmogenic isotope to estimate average soil transport rates over 3,500 years; rate of creep is proportional to surface gradient.

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  • Montgomery, D. R. 2007. Dirt: The erosion of civilizations. Berkeley: Univ. of California Press.

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    Comprehensive historical review of the causes and consequences of soil erosion around the world, in a nontechnical format written to be accessible to general readers.

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  • Morgan, R. P. C. 2005. Soil erosion and conservation. 3d ed. Oxford: Blackwell.

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    More technical treatment than Montgomery 2007; covers processes and mechanics of soil erosion, factors influencing soil erosion, assessment and measurement of soil erosion, modeling soil erosion, and methods for mitigating soil erosion.

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  • Thomas, P. J., J. C. Baker, and L. W. Zelazny. 2000. An expansive soil index for predicting shrink-swell potential. Soil Science Society of America Journal 64:268–274.

    DOI: 10.2136/sssaj2000.641268xSave Citation »Export Citation »E-mail Citation »

    Quantifies the shrink-swell potential of soils in Virginia, United States, based on soil mineralogy, particle size distribution, liquid limit, plasticity index, and cation-exchange capacity; soils prone to shrinking and swelling tend to have high clay contents.

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  • Xu, L., X. Xu, and X. Meng. 2013. Risk assessment of soil erosion in different rainfall scenarios by RUSLE model coupled with Information Diffusion Model: A case study of Bohai Rim, China. Catena 100:74–82.

    DOI: 10.1016/j.catena.2012.08.012Save Citation »Export Citation »E-mail Citation »

    Employs the RUSLE model to evaluate the risk of soil erosion under different rainfall scenarios and to identify factors such as rainfall intensity and vegetation cover that influence soil erosion.

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A tsunami is an anomalously large wave generated by energy transmitted through the ocean, typically from a submarine, earthquake, or landslide. The word, which is in common use around the world, comes from Japan and reflects the numerous tsunamis that have battered Japan throughout the nation’s history. Tsunamis are hazardous because they can be so enormous and can occur with little warning if the associated earthquake is not sufficiently close or strong to cause noticeable tremors in the coastal areas affected by the tsunami. Environmental geology includes mapping the geographic distribution of tsunamis and deposits that can be used to infer the occurrence of ancient tsunamis, as reviewed in Dawson and Shi 2000. Frohlich, et al. 2009 provides a case study of using coastal boulder deposits to infer a prehistoric tsunami in Tonga. Nott 2000 uses boulder deposits to investigate prehistoric tsunamis affecting coastal tropical Australia, and Nanayama, et al. 2003 uses sand sheets to develop a record of prehistoric tsunamis affecting Japan. Shaw, et al. 2008 draws on multiple lines of evidence, including numerical modeling, to constrain the characteristics of a tsunami described in historical accounts from widely separated locations around the Mediterranean Sea. Environmental geology also includes investigating the tectonic conditions and coastal configuration that influence the magnitude and frequency of tsunamis, as illustrated for the Indian Ocean basin in Okal and Synolakis 2008 and in Ten Brink, et al. 2006 for the region around Puerto Rico. Finally, environmental geologists assist in developing systems for prediction and warning of tsunami hazards. Satake 2005 provides a comprehensive overview of all of these aspects of environmental geology approaches to tsunami hazards.

  • Dawson, A., and S. Shi. 2000. Tsunami deposits. Pure and Applied Geophysics 157:875–897.

    DOI: 10.1007/s000240050010Save Citation »Export Citation »E-mail Citation »

    Summarizes current knowledge of tsunami deposits and discusses the discrepancy between geological studies of ancient tsunami deposits in coastal sediments and lack of geological characterization of process and depositional features in modern tsunamis.

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  • Frohlich, C., M. J. Hornbach, F. W. Taylor, et al. 2009. Huge erratic boulders in Tonga deposited by a prehistoric tsunami. Geology 37:131–134.

    DOI: 10.1130/G25277A.1Save Citation »Export Citation »E-mail Citation »

    Uses thorium-isotope dating of coral limestone boulders lying ten to twenty meters above sea level to constrain age of rock formation (120,000–130,000 years ago) and computer modeling to investigate scenarios that could move the boulders to their present locations; results suggest a tsunami generated by submarine hillslope failures.

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  • Nanayama, F., K. Satake, R. Furukawa, et al. 2003. Unusually large earthquakes inferred from tsunami deposits along the Kuril trench. Nature 424:660–663.

    DOI: 10.1038/nature01864Save Citation »Export Citation »E-mail Citation »

    Constrains the ages of tsunami-deposited sheets of sand that extend far inland from the Japanese coast using interbedded volcanic ash layers; unusually large tsunamis occurred on average every five hundred years during the past seven thousand years; these frequent tsunamis result from fault movements along the southern Kuril trench where the Pacific and Eurasian tectonic plates converge.

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  • Nott, J. 2000. Records of prehistoric tsunamis from boulder deposits—evidence from Australia. Science of Tsunami Hazards 18:3–14.

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    Boulder deposits along the tropical Australian coast record tsunamis and tropical cyclones; uses deposits created by a 1998 tsunami in Papua New Guinea to calibrate relations between flow depth and boulder transport.

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  • Okal, E. A., and C. E. Synolakis. 2008. Far-field tsunami hazard from mega-thrust earthquakes in the Indian Ocean. Geophysical Journal International 172:995–1015.

    DOI: 10.1111/j.1365-246X.2007.03674.xSave Citation »Export Citation »E-mail Citation »

    Uses numerical models of seismic ruptures to investigate potential effects on tsunami hazard of factors such as location and magnitude of rupture; results suggest that many coastal regions around the Indian Ocean could experience larger tsunamis than the 2004 event that caused substantial death and destruction.

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  • Satake, K., ed. 2005. Tsunamis: Case studies and recent developments. Dordrecht, The Netherlands: Springer.

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    Edited volume covering case studies around the world; discusses geologic records of past tsunamis, numerical modeling of tsunami processes and hazards, mapping of tsunami hazards, forecasting occurrence of tsunamis, and the effects of coastal vegetation and topography on mitigating hazards.

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  • Shaw, B., N. N. Ambraseys, P. C. England, et al. 2008. Eastern Mediterranean tectonics and tsunami hazard inferred from the AD 365 earthquake. Nature Geoscience 1:268–276.

    DOI: 10.1038/ngeo151Save Citation »Export Citation »E-mail Citation »

    Uses field mapping and geochronology to characterize an enormous tsunami previously known only from historical accounts; nice example of a geologic detective story involving paleo-fault movement and a tsunami.

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  • Ten Brink, U. S., E. L. Geist, and B. D. Andrews. 2006. Size distribution of submarine landslides and its implication to tsunami hazard in Puerto Rico. Geophysical Research Letters 33:L11307.

    DOI: 10.1029/2006GL026125Save Citation »Export Citation »E-mail Citation »

    Uses bathymetry to characterize the sizes of submarine landslides, then couples the landslide volume-area relationship with tsunami simulations to estimate tsunami size in the region.

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Volcanoes involve the release of molten rock, magmatic water, and gases at the surface. This release can be extremely abrupt and violent, as in a pyroclastic flow that involves a glowing cloud of hot ash and gases moving at tremendous speeds, or the release can take the form of a relatively slow and nonviolent flow of basaltic magma from a vent or fissure. Whatever the details of the volcanic eruption, the magma released is likely to create natural hazards, as comprehensively reviewed in Blong 1984. Many of these are secondary hazards, such as volcanic heat that melts glacial ice and triggers outburst floods known as jökulhlaups, or eruptions that cause volcanic crater lakes to overflow and trigger lahars, as discussed in Graettinger, et al. 2010 and Gudmundsson, et al. 1997. As with other forms of natural hazards, environmental geologists map the geographic distribution of volcanic eruptions and characterize the magnitude and frequency of eruptions within a region or from a specific volcano by drawing on geologic indicators of past eruptions and numerical models of magma behavior. Molloy, et al. 2009 reconstructs the history of volcanic eruptions in the Auckland volcanic field of New Zealand using volcanic deposits in lakes. Dobran, et al. 1994 uses a numerical model to infer that a large eruption at Vesuvius could devastate the surroundings to a distance of seven kilometers on all sides within fifteen minutes. Finn, et al. 2007 employs magnetic surveys to map the distribution of hydrothermally altered rocks as an indicator of potential source zones for future lahars, or volcanically induced debris flows. Environmental geologists also work with people from other disciplines to develop prediction and warning systems for volcanic eruptions. A particularly interesting example is Bird, et al. 2010, which investigates perceptions of volcanic risk in Iceland. Tourists from other countries tend to be ignorant of volcanic hazards such as jökulhlaups. Tourists are receptive to receiving information on hazards, but tourism employees are averse to communicating this information. Calderazzo 2004 discusses the geologic underpinnings of volcanism and human perceptions of volcanoes through time and across different cultures.

  • Bird, D. K., G. Gisladottir, and D. Dominey-Howes. 2010. Volcanic risk and tourism in southern Iceland: Implications for hazard, risk and emergency response education and training. Journal of Volcanology and Geothermal Research 189:33–48.

    DOI: 10.1016/j.jvolgeores.2009.09.020Save Citation »Export Citation »E-mail Citation »

    Volcanoes in Iceland are particularly likely to trigger catastrophic outburst floods known as jökulhlaups; early warning systems and emergency response procedures must consider the relative ignorance of tourists from areas that do not have volcanic hazards, as well as persuading tourism employees to effectively disseminate relevant information.

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  • Blong, R. J. 1984. Volcanic hazards: A sourcebook on the effects of eruptions. North Ryde, Australia: Academic Press Australia.

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    Reviews types and distribution of volcanic activity and hazards associated with lava flows, ballistic projectiles and tephra, pyroclastic flows and debris avalanches, lahars and jökulhlaups, earthquakes and ground deformation, tsunamis, atmospheric phenomena, acid rains and gases, and effects on societies and infrastructure.

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  • Calderazzo, J. 2004. Rising fire: Volcanoes and our inner lives. Guilford, CT: Lyons.

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    A highly readable account of the geologic underpinnings of volcanism and human perceptions of volcanoes across different cultures; includes some page-turning accounts of hazards far from the actual volcanic source, such as ash clouds that affect commercial air traffic.

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  • Dobran, F., A. Neri, and M. Todesco. 1994. Assessing the pyroclastic flow hazard at Vesuvius. Nature 367:551–554.

    DOI: 10.1038/367551a0Save Citation »Export Citation »E-mail Citation »

    Uses numerical simulations to assess hazards associated with pyroclastic flows (volcanic avalanches) at one of the world’s most famous volcanoes; results suggest that large eruptions can create complete destruction within a seven-kilometer radius of the volcano, an area currently occupied by a million people, within fifteen minutes or less.

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  • Finn, C. A., M. Deszcz-Pan, E. D. Anderson, and D. A. John. 2007. Three-dimensional geophysical mapping of rock alteration and water content at Mount Adams, Washington: Implications for lahar hazards. Journal of Geophysical Research Solid Earth 112:B10204.

    DOI: 10.1029/2006JB004783Save Citation »Export Citation »E-mail Citation »

    Lahars are debris flows originating from volcanoes via collapse of hydrothermally altered and water-saturated rocks; hydrothermal alteration changes rock resistivity and magnetization in a manner that can be identified with helicopter electromagnetic measurements; along with geologic mapping and measurements of rock properties, this can be used to identify source zones for future large debris flows.

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  • Graettinger, A. H., V. Manville, and R. M. Briggs. 2010. Depositional record of historic lahars in the upper Whangaehu Valley, Mt. Ruapehu, New Zealand: Implications for trigger mechanisms, flow dynamics and lahar hazards. Bulletin of Volcanology 72:279–296.

    DOI: 10.1007/s00445-009-0318-2Save Citation »Export Citation »E-mail Citation »

    Lahars on Mount Ruapehu result from explosive eruptions or subsurface magma movements that displace volcanic crater lake water onto adjacent slopes; from rain remobilization of tephra deposits on steep slopes; and from lake breakouts via breaching of temporary tephra or ice dams; develops magnitude-frequency relationships for lahars.

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  • Gudmundsson, M. T., F. Sigmundsson, and H. Björnsson. 1997. Ice-volcano interaction of the 1996 Gjálp subglacial eruption, Vatnajökull, Iceland. Nature 389:954–957.

    DOI: 10.1038/40122Save Citation »Export Citation »E-mail Citation »

    Detailed investigation of the mechanics of volcanic eruptions under glaciers and the resulting jökulhlaups, lahars, and potential changes in glacial size and movement; uses a case study from the 1996 fissure eruption at Vatnajökull in Iceland.

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  • Molloy, C., P. Shane, and P. Augustinus. 2009. Eruption recurrence rates in a basaltic volcanic field based on tephra layers in maar sediments: Implications for hazards in the Auckland volcanic field. Geological Society of America Bulletin 121:1666–1677.

    DOI: 10.1130/B26447.1Save Citation »Export Citation »E-mail Citation »

    Develops an eruption chronology for the Auckland volcanic field using basalt tephra layers deposited in maar lakes; recurrence times of less than five hundred years to twenty thousand years show no temporal trend, making it difficult to forecast volcanic hazards.

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Although naturally started forest and grass fires can occur in many environments, wildfires are of particular concern in arid to semiarid regions such as interior Australia and the western United States. Atmospheric scientists, forest ecologists, and fire scientists investigate the mechanics of wildfire and prediction and warning systems. Environmental geologists focus on the secondary effects of wildfire, such as enhanced erosion and deposition of sediment, hillslope failures, and flooding. Moody and Martin 2001 discusses changes in water and sediment movement following a 1996 wildfire in Colorado. Moody, et al. 2008 develops an erodibility index based on portion of available stream power used to move sediment. Nyman, et al. 2011 characterizes postfire debris flows triggered by intense, short duration precipitation in Australia. Shakesby 2011 provides a thorough and comprehensive review of both how human landscape modifications influence fire magnitude and frequency, and how fires affect hydrology, soil characteristics, and erosion. Environmental geologists also reconstruct long-term records of fire recurrence using tree rings and various types of sedimentary deposits. Meyer, et al. 1992 and Pierce, et al. 2004 present these types of reconstructed fire chronologies based on alluvial fan sediments in the western United States. Swetnam and Baisan 2003 uses fire scars in tree rings from sites across the southwestern United States to develop a regional history of wildfire. Pyne 1997 examines in detail the interactions between wildfire and human societies, using the United States as a focal region.

  • Meyer, G. A., S. G. Wells, R. C. Balling, and A. J. T. Jull. 1992. Response of alluvial systems to fire and climate change in Yellowstone National Park. Nature 357:147–150.

    DOI: 10.1038/357147a0Save Citation »Export Citation »E-mail Citation »

    Uses alluvial fan sediments to reconstruct the history of fires over the past 3,500 years in Yellowstone; fans aggrade during periods of frequent wildfire, which correspond to times of drought or high climatic variability.

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  • Moody, J. A., and D. A. Martin. 2001. Initial hydrologic and geomorphic response following a wildfire in the Colorado Front Range. Earth Surface Processes and Landforms 26:1049–1070.

    DOI: 10.1002/esp.253Save Citation »Export Citation »E-mail Citation »

    Case study of how reduced erosion threshold following wildfire can magnify hillslope and channel responses to rainfall during the first four years after fire; more than half of the sediment eroded from hillslopes remained in the watershed four years after the fire, with an estimated sediment residence time of three hundred years.

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  • Moody, J. A., D. A. Martin, and S. H. Cannon. 2008. Post-wildfire erosion response in two geologic terrains in the western USA. Geomorphology 95:103–118.

    DOI: 10.1016/j.geomorph.2007.05.011Save Citation »Export Citation »E-mail Citation »

    Develops an index to facilitate comparison of erosional response to precipitation following wildfire in different regions; part of the response depends on the continuing availability of sediment, which can be exhausted relatively quickly in terrains underlain by bedrock that weathers slowly.

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  • Nyman, P., G. J. Sheridan, H. G. Smith, and P. N. J. Lane. 2011. Evidence of debris flow occurrence after wildfire in upland catchments of south-east Australia. Geomorphology 125:383–401.

    DOI: 10.1016/j.geomorph.2010.10.016Save Citation »Export Citation »E-mail Citation »

    Investigates debris flows occurring after wildfires in southeastern Australia; quantifies erosion rates and rainfall thresholds for debris flows, which are triggered by intense, short duration, infrequent rainfalls; concludes that debris flows are an important postfire hazard.

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  • Pierce, J. L., G. A. Meyer, and A. J. T. Jull. 2004. Fire-induced erosion and millennial-scale climate change in northern ponderosa pine forests. Nature 432:87–90.

    DOI: 10.1038/nature03058Save Citation »Export Citation »E-mail Citation »

    Uses alluvial fan sediments in central Idaho, United States, to reconstruct Holocene fire history and links fire regime to climate; colder periods correspond to frequent, low-severity fires; warmer periods of drought correspond to stand-replacing fires and large debris flows.

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  • Pyne, S. J. 1997. Fire in America: A cultural history of wildland and rural fire. Seattle: Univ. of Washington Press.

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    Thorough and compelling treatment of the history of human interactions with fires, focusing particularly on the United States; also discusses the science of wildfire and hazards associated with fires; one of several books by this author, who is the leading authority on wildfire in a historical and cultural context.

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  • Shakesby, R. A. 2011. Post-wildfire soil erosion in the Mediterranean: Review and future research directions. Earth-Science Reviews 105:71–100.

    DOI: 10.1016/j.earscirev.2011.01.001Save Citation »Export Citation »E-mail Citation »

    Warming and drying climate and changes in land cover have led to substantial increases in wildfires in the European Mediterranean region since the 1960s; focuses on the history of human landscape alterations as an influence on wildfires; reviews fire impacts on hydrology, soil properties, and erosion.

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  • Swetnam, T. W., and C. H. Baisan. 2003. Tree-ring reconstructions of fire and climate history in the Sierra Nevada and southwestern United States. In Fire and climatic change in temperate ecosystems of the western Americas. Edited by T. T. Veblen, W. L. Baker, G. Montenegro, and T. W. Swetnam, 158–195. New York: Springer.

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    Describes fire-scar chronologies from tree rings in semiarid forests across Arizona, New Mexico, and the western side of the Sierra Nevada in California; nice example of using site-specific records from multiple sites to gain insight into regional fire history and factors controlling fire magnitude and frequency.

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Resource use, Hazards, and Sustainability

The section Natural Hazards discusses aspects of environmental geology related to hazards associated with naturally occurring processes such as earthquakes or wildfire, although the magnitude, frequency, and geographic distribution of these processes can be altered by human activities. This section discusses how environmental geology relates to hazards specifically associated with, or created by, resource use. The resources treated in this section are construction aggregate, minerals, building stone, soil, timber, and surface and ground water. This section also covers hazards associated with development of transportation corridors such as roads and with urbanization. Environmental geologists sometimes map or characterize the distribution of natural resources that result from near-surface geologic processes, such as sand and gravel deposits used for aggregate in construction, or surface and ground water supplies, particularly in the context of evaluating sustainable use of these resources. More commonly, environmental geologists address hazards resulting from use of natural resources. Such hazards include subsidence from removal of subsurface materials; accelerated erosion deposition and associated hillslope and river instability; and contamination of soils, ground, and surface waters. The works cited here address each of these issues in the context of the different natural resources and land uses discussed.

Construction Aggregate

Sand and gravel are critical components of many forms of construction, from road and railroad substrates to cement. Sand and very fine gravel are also used as traction sand to reduce hazards associated with ice on roads. Environmental geologists are involved in locating and assessing the volume and grain-size distribution of sediments used as construction aggregate, as illustrated in van der Meulen, et al. 2005, but most environmental geology related to these materials focuses on hazards associated with aggregate mining. Hazards in the form of accelerated erosion and deposition especially affect hillslope and river environments; Kondolf 1997 introduced the phrase “hungry waters,” which is now widely used, to describe rivers deprived of sediment and consequently prone to erosion of the channel bed and banks downstream from the dam or gravel-mining site that reduces sediment supply to the river. Padmalal, et al. 2008 provides a case study of the effects of hungry waters in India, where extraction of millions of tons of sediment from river channels and floodplains is causing substantial river incision. Extraction of sand and gravel can also influence the presence and characteristics of shallow aquifers that supply drinking water, as discussed in Peckenham, et al. 2009. Many rivers are affected by multiple forms of resource use, including aggregate mining, as discussed in Surian and Rinaldi 2003. Introduction of excess sediment to a river from tailings associated with placer mining can severely affect the river, as discussed in the section Minerals, but Nelson and Church 2012 documents a scenario where a large river remains stable under such sediment inputs because the flow is capable of moving all of the extra sediment. A particularly distinctive hazard associated with mining of construction aggregate is the disappearance of Pleistocene glacial landforms composed of sand and gravel that is extracted until the landform is gone, as discussed in Woodcock, et al. 2012. Mining-related destruction of landforms such as drumlins and eskers has led to proposals to distinguish endangered landforms and to protect geodiversity and geoheritage, as discussed in Gray 2008.

  • Gray, M. 2008. Geoheritage 1. Geodiversity: A new paradigm for valuing and conserving geoheritage. Geoscience Canada 35:51–59.

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    Geodiversity was proposed in 1993 as an analogue to biodiversity; geoconservation sites are chosen to represent the geodiversity of a region; geoconservation sites may focus on protection of static features or protection of processes; among the most threatened features are eskers, drumlins, limestone pavements, and volcanic cones mined for cinders.

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  • Kondolf, G. M. 1997. Hungry water: Effects of dams and gravel mining on river channels. Environmental Management 21:533–551.

    DOI: 10.1007/s002679900048Save Citation »Export Citation »E-mail Citation »

    River form reflects the balance of water and sediment inputs; dams and gravel mining reduce downstream sediment supply, causing accelerated erosion of the channel bed and banks, coarsening of bed grain sizes, and loss of spawning sites or other stream habitat; also considers reduced river transport of sediment and associated coastal erosion.

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  • Nelson, A., and M. A. Church. 2012. Placer mining along Fraser River, British Columbia: The geomorphic impact. Geological Society of America Bulletin 124:1212–1228.

    DOI: 10.1130/B30575.1Save Citation »Export Citation »E-mail Citation »

    Nineteenth-century placer mining tailings increase sand and gravel inputs to the Fraser River; the river remains stable because the flow is capable of moving the volume of introduced sediment, but effects of excess sediment are concentrated in lower gradient river segments.

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  • Padmalal, D., K. Maya, S. Sreebha, and R. Sreeja. 2008. Environmental effects of river sand mining: A case from the river catchments of Vembanad Lake, southwest coast of India. Environmental Geology 54:879–889.

    DOI: 10.1007/s00254-007-0870-zSave Citation »Export Citation »E-mail Citation »

    Rapidly growing urban centers in India are associated with extensive and unregulated aggregate mining from river channels and floodplains; the volume of sediment removed is about forty times higher than estimated sediment inputs, leading to substantial river incision in the late 20th and early 21st centuries.

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  • Peckenham, J. M., T. Thornton, and B. Whalen. 2009. Sand and gravel mining: Effects on ground water resources in Hancock County, Maine, USA. Environmental Geology 56:1103–1114.

    DOI: 10.1007/s00254-008-1210-7Save Citation »Export Citation »E-mail Citation »

    Sand and gravel deposits provide shallow aquifers used to supply drinking water; this study tests metrics to measure the effectiveness of gravel mining regulations at protecting aquifers and aquifer vulnerability to contamination.

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  • Surian, N., and M. Rinaldi. 2003. Morphological response to river engineering and management in alluvial channels in Italy. Geomorphology 50:307–326.

    DOI: 10.1016/S0169-555X(02)00219-2Save Citation »Export Citation »E-mail Citation »

    Combined effects of sediment extraction, dams, and channelization have caused widespread changes in Italian rivers, including incision and narrowing; study examines differences in rate and style of river adjustment in relation to size and pre-disturbance planform of the river, as well as the intensity and type of human alteration.

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  • van der Meulen, M. J., S. F. van Gessel, and J. G. Veldkamp. 2005. Aggregate resources in the Netherlands. Netherlands Journal of Geosciences 84:379–387.

    DOI: 10.1017/S0016774600021193Save Citation »Export Citation »E-mail Citation »

    Used 350,000 borehole logs to build 3-D stratigraphic model and map aggregate resources down to fifty meters below the surface; can be used to estimate total volume and specific locations and extent of aggregate for mining.

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  • Woodcock, D. W., J. S. Rogan, and S. D. Blanchard. 2012. Accelerating anthropogenic land surface change and the status of Pleistocene drumlins in New England. PLoS ONE 7:e46702.

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    Surveyed location and human alteration of drumlins in eastern Massachusetts; discusses environmental consequences of drumlin alteration and factors driving such alteration, including continuing sprawl and development of remaining land, building practices, and lack of explicit rationale for preserving the region’s geoheritage.

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Economic geologists locate mineral resources and characterize their extent and quality, and mining engineers oversee extraction of the minerals. Environmental geologists are primarily involved in identifying and mitigating the negative environmental consequences of mining, which include hillslope instability; excess sediment deposition in rivers, lakes, and wetlands; and surface and ground water contamination. The works cited here provide example case studies of these activities. Gilbert 1917 represents the first systematic study of excess sediment introduced to river systems as a result of historical placer mining in the Sierra Nevada of California. The paper is a classic in the disciplines of environmental geology and geomorphology. James, et al. 2009 provides an update on work in the same region and discusses some of the nuances of differences in rates and styles of change among individual rivers. Macklin, et al. 2003 uses water and sediment samples to assess continuing contamination of portions of the Danube River following tailings-dam failures in the mountains of Romania. Miller, et al. 1996 and Stoughton and Marcus 2000 provide examples of studies assessing the distribution and impact of much older historical metal mining in the western United States. Coulthard and Macklin 2003 numerically model the extent of contaminated sediments in river systems affected by historical metal mining. Hettler, et al. 1997 represents the numerous studies associated with the massive contamination of the Ok Tedi-Fly River system in Papua New Guinea by copper-enriched sediments released from a headwater copper-gold porphyry mine. Mudd 2001 discusses persistent effects of in situ leach uranium mining on groundwater quality.

  • Coulthard, T. J., and M. G. Macklin. 2003. Modeling long-term contamination in river systems from historical metal mining. Geology 31:451–454.

    DOI: 10.1130/0091-7613(2003)031<0451:MLCIRS>2.0.CO;2Save Citation »Export Citation »E-mail Citation »

    Describes a catchment-scale sediment model that uses historical mining records to predict contemporary and future levels and patterns of sediment contamination within river systems; simulations of the effects of future climate changes in the study area of northern England indicate that increasing flooding will dilute surface contamination from past mining.

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  • Gilbert, G. K. 1917. Hydraulic mining debris in the Sierra Nevada. Washington, DC: US Government Printing Office.

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    First systematic study of the effects of excess sediment on rivers in the Sierra Nevada; combines field studies and flume experiments to understand how sediment disperses or concentrates between the source area and the terminus of the river; definitely still worth reading a century after publication.

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  • Hettler, J., G. Irion, and B. Lehmann. 1997. Environmental impact of mining waste disposal on a tropical lowland river system: A case study on the Ok Tedi Mine, Papua New Guinea. Mineralium Deposita 32:280–291.

    DOI: 10.1007/s001260050093Save Citation »Export Citation »E-mail Citation »

    Case study of an infamous example of excess sediment and chemical contamination of a large river system and downstream marine environments as a result of copper-gold mining in the headwaters; the one-thousand-kilometer-long Ok Ted-Fly River system receives sixty-six million tons of contaminated sediment each year, which is dispersed across floodplains.

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  • James, L. A., M. B. Singer, S. Ghoshal, and M. Megison. 2009. Historical channel changes in the lower Yuba and Feather Rivers, California: Long-term effects of contrasting river-management strategies. In Management and restoration of fluvial systems with broad historical changes and human impacts. Edited by L. A. James, S. L. Rathburn, and G. R. Whittecar, 57–81. Special Paper 451. Boulder, CO: Geological Society of America.

    DOI: 10.1130/2009.2451(04)Save Citation »Export Citation »E-mail Citation »

    Updates the work of Gilbert 1917 on the effects of placer mining sediment on rivers of California’s Sierra Nevada; effects include severe aggradation, but rates and details of channel and floodplain change vary among individual rivers as a result of different river-management strategies as well as differences in river and mining history.

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  • Macklin, M. G., P. A. Brewer, D. Balteanu, et al. 2003. The long term fate and environmental significance of contaminant metals released by the January and March 2000 mining tailings dam failures in Maramures County, upper Tisa Basin, Romania. Applied Geochemistry 18:241–257.

    DOI: 10.1016/S0883-2927(02)00123-3Save Citation »Export Citation »E-mail Citation »

    Uses samples of surface water and channel and floodplain sediments to assess continuing patterns of metal contamination following failures of mining-tailings dams in headwater tributaries of the Danube River.

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  • Miller, J. R., J. Rowland, P. J. Lechler, M. Desilets, and L. C. Hsu. 1996. Dispersal of mercury-contaminated sediments by geomorphic processes, Sixmile Canyon, Nevada, USA: Implications to site characterization and remediation of fluvial environments. Water, Air, and Soil Pollution 86:373–388.

    DOI: 10.1007/BF00279168Save Citation »Export Citation »E-mail Citation »

    Nineteenth-century gold and silver mining used mercury to process the precious metals, and substantial quantities of mercury were released along with tailings into the Carson River drainage; study uses geomorphic and geochemical data to document the distribution, quantity, and physical dispersal of mercury-contaminated sediment during the century since mining.

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  • Mudd, G. M. 2001. Critical review of acid in situ leach uranium mining: 1. USA and Australia. Environmental Geology 41:390–403.

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    In situ leach uranium mining can create problems of secondary precipitation, higher salinity, and heavy metal and radionuclide pollution of groundwater; examines history of such mining sites in the United States and Australia to evaluate whether natural attenuation is capable of restoring groundwater quality.

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  • Stoughton, J. A., and W. A. Marcus. 2000. Persistent impacts of trace metals from mining on floodplain grass communities along Soda Butte Creek, Yellowstone National Park. Environmental Management 25:305–320.

    DOI: 10.1007/s002679910024Save Citation »Export Citation »E-mail Citation »

    Examines the effects on riparian plants of mining-contaminated sediments deposited along a river system; documents a threshold relationship between metal concentrations and plant characteristics; vegetation diversity, density, and biomass decrease at threshold levels of trace metal concentrations and soil pH.

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In this context, rock refers to decorative stone used for building and includes sedimentary, metamorphic, and igneous lithologies. Petrologists and mining engineers are more likely to be involved in locating, mapping, and extracting such rock, but environmental geologists deal with the negative environmental effects of this form of mining. Primary among these negative effects, in terms of geologic processes, are slope instability associated with removal of material, as illustrated in the case study in Koca and Kincal 2004, and excess sedimentation resulting from erosion of waste rock. Sinha, et al. 2000 describes a case study where quarrying of sandstone also affected forest resources and surface water and groundwater supplies. Environmental geologists may also be involved in assessing deterioration of building stone as a result of natural or human-accelerated weathering processes, as illustrated in Cardell, et al. 2003 and Rothert, et al. 2007.

  • Cardell, C., F. Delalieux, K. Roumpopoulos, A. Moropoulou, F. Auger, and R. Van Grieken. 2003. Salt-induced decay in calcareous stone monuments and buildings in a marine environment in SW France. Construction and Building Materials 17:165–179.

    DOI: 10.1016/S0950-0618(02)00104-6Save Citation »Export Citation »E-mail Citation »

    Salt weathering affects rock exposed to the air or to fluctuating subsurface moisture levels; study assesses weathering mechanisms in calcareous rocks used in monuments and buildings in southwestern France, where proximity to the coast accelerates salt weathering; weathering varies depending on rock porosity and rates of salt input.

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  • Koca, M. Y., and C. Kincal. 2004. Abandoned stone quarries in and around the Izmir city centre and their geo-environmental impacts—Turkey. Engineering Geology 75:49–67.

    DOI: 10.1016/j.enggeo.2004.05.001Save Citation »Export Citation »E-mail Citation »

    Abandoned quarries in an urban area of Turkey pose hazards via slope instability in the form of sliding and toppling; discusses slope stability analyses to map potential future hazards.

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  • Rothert, E., T. Eggers, J. Cassar, J. Ruedrich, B. Fitzner, and S. Siegesmund. 2007. Stone properties and weathering induced by salt crystallization of Maltese Globigerina Limestone. Geological Society London Special Publications 271:189–198.

    DOI: 10.1144/GSL.SP.2007.271.01.19Save Citation »Export Citation »E-mail Citation »

    Case study of accelerated weathering of limestone used in monuments and buildings in a coastal environment; extent of salt weathering reflects salt type and concentration, as well as rock pore space characteristics.

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  • Sinha, R. K., D. K. Pandey, and A. K. Sinha. 2000. Mining and the environment: A case study from Bijolia quarrying site in Rahasthan, India. The Environmentalist 20:195–203.

    DOI: 10.1023/A:1006795529201Save Citation »Export Citation »E-mail Citation »

    Fissile sandstones quarried for roofing and flooring in this case study; documents deforestation resulting from mining and enhanced use of firewood and tools by miners, as well as dust and air pollution and changes in groundwater and river flow.

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Sand Encroachment

Sand encroachment refers to accumulation of windblown sand on infrastructure such as roads and buildings, on agricultural lands, and in other areas used or inhabited by people. Although accumulation of windblown sand is a natural process that creates coastal beaches and inland sand dunes, human activities can both exacerbate wind erosion and mobilization of sand, and block the transport of sand in a manner that creates large sand deposits within human-altered environments. In extreme examples, large sand dunes can completely bury entire villages or sections of road. Vegetation tends to limit sand mobilization, so regions with sand encroachment problems are typically arid or semiarid. A common scenario is that land uses such as grazing of domestic animals or urbanization remove native vegetation, which increases the mobility of sand grains, and the sand then accumulates in a manner that creates hazards for people and infrastructure. Khalaf and al-Ajmi 1993 presents a representative case study from the Middle East where rapid economic growth during the later decades of the 20th century led to extensive land-use changes and associated increases in sand erosion and encroachment. Sand encroachment continues to be a major problem in this geographic region, and Boulghobra, et al. 2015 describes the use of remote imagery to monitor sand movement over larger spatial and longer time scales. Sub-Saharan Africa is also severely affected by sand encroachment, as comprehensively reviewed for Mauritania in Berte 2010. Gao, et al. 2002 discusses use of revegetation to limit sand encroachment in an arid region of China.

  • Berte, C. J. 2010. Fighting sand encroachment: Lessons from Mauritania. FAO Forestry Paper 158. Rome: Food and Agriculture Organization of the United Nations.

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    Mauritania is especially severely affected by sand encroachment; this publication reviews the history of sand encroachment in the country and the lessons learned with regard to land use and managing mobile sand, and discusses a successful revegetation project designed to limit sand encroachment.

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  • Boulghobra, N., S. Merdas, and L. Fattoum. 2015. Sand encroachment in the Saharan Algeria: The not declared disaster—case study; In-Salah region in the Tidikelt. Planet @ Risk 3:72–76.

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    Uses remote sensing to monitor mobile dunes over a period of nineteen years; information used to identify areas susceptible to sand encroachment and to recommend mitigation strategies.

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  • Gao, Y., et al. 2002. A 10-year study on techniques for vegetation restoration in a desertified salt lake area. Journal of Arid Environments 52:483–497.

    DOI: 10.1006/jare.2002.1013Save Citation »Export Citation »E-mail Citation »

    Restoring vegetation in arid regions can be very difficult; examines the cost and effectiveness of different afforestation methods as applied to an arid site in China and draws broader conclusions applicable to other regions.

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  • Khalaf, F. I., and D. al-Ajmi. 1993. Aeolian processes and sand encroachment problems in Kuwait. Geomorphology 6:111–134.

    DOI: 10.1016/0169-555X(93)90042-ZSave Citation »Export Citation »E-mail Citation »

    Reviews the causes and consequences of sand encroachment during the late 20th century in Kuwait and discusses passive and active control measures to limit sand encroachment; passive measures involve land use and active measures employ techniques to stabilize land surfaces and trap mobile sand.

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Soil Erosion

Environmental geologists are among the scientists from diverse disciplines who work on soil erosion because it is such a critical issue. Erosion of fertile soil layers that require hundreds of years to develop represents a form of soil mining that impoverishes soils and requires increasingly intense application of artificial fertilizers to maintain crop production. Deposition of eroded topsoil in lower-energy environments such as river floodplains, wetlands, and nearshore areas creates numerous secondary problems for biota in these environments, as discussed in Happ 1945. Marsh 1865 is one of the first works to discuss these issues and in this sense is a foundational book for environmental geology, but the effects of land clearance and soil erosion have been occurring for thousands of years, as reviewed in van Andel, et al. 1990. Among the aspects of soil erosion that are of concern to environmental geologists are causes of soil erosion and rates and magnitudes of different erosional processes and of soil erosion in general across different environments, as discussed in Brazier 2004. Environmental geologists work to develop long-term perspectives on soil erosion from sediments at depositional sites, as reviewed in Dotterweich 2008, and isotopic ratios of eroded and deposited sediment, as discussed in Ritchie and McHenry 1990. Environmental geologists also investigate the environmental effects of soil deposition. Trimble 2013 provides detailed investigations of the multi-decadal response of one region to clearing of native land cover and subsequent reforestation, including the details of channel adjustments across space and through time. Montgomery 2007 provides a thorough overview of all aspects of soil erosion. Many of the works cited here address soil erosion occurring primarily via water. Soil can also be eroded by wind, as most dramatically revealed during the 1930s Dust Bowl in the United States. Li, et al. 2007 specifically addresses soil erosion via wind in a desert grassland in New Mexico, United States. Soil crusts, whether formed by concentration of fine-grained cohesive silt or clay or biological features such as lichens, exert an important control on wind erosion of soil, as reviewed in Belnap 2003. Additional works are cited in this article within the sections on Natural Hazards and Soils.

  • Belnap, J. 2003. Biological soil crusts and wind erosion. In Biological soil crusts: Structure, function, and management. Edited by J. Belnap and O. L. Lange, 339–347. Berlin: Springer.

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    Reviews the influence of biological soil crusts in limiting wind erosion of soils and describes how destruction of these fragile crusts can result in greatly accelerated wind erosion.

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  • Brazier, R. 2004. Quantifying soil erosion by water in the UK: A review of monitoring and modelling approaches. Progress in Physical Geography 28:340–365.

    DOI: 10.1191/0309133304pp415raSave Citation »Export Citation »E-mail Citation »

    Synthesizes available data from the United Kingdom to characterize rates of hillslope and catchment erosion and relates these rates to soil type and land use; discusses the shift from erosion monitoring to erosion modeling and the implications for understanding and modeling erosion.

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  • Dotterweich, M. 2008. The history of soil erosion and fluvial deposits in small catchments of central Europe: Deciphering the long-term interaction between humans and the environment—a review. Geomorphology 101:192–208.

    DOI: 10.1016/j.geomorph.2008.05.023Save Citation »Export Citation »E-mail Citation »

    Synthesizes results from multiple studies of historical upland soil erosion and river valley aggradation in central Europe; sediment fluxes in small catchments are highly sensitive to local land use, whereas river sediments in larger drainages reflect regional patterns of land use and climate; notes the importance of extreme events such as large floods.

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  • Happ, S. C. 1945. Sedimentation in South Carolina Piedmont valleys. American Journal of Science 243:113–126.

    DOI: 10.2475/ajs.243.3.113Save Citation »Export Citation »E-mail Citation »

    Classic study of how upland soil erosion associated with agriculture results in floodplain aggradation during succeeding decades; more than a meter of floodplain aggradation results in exacerbated flooding and loss of fertile bottomland soils through burial; many subsequent studies have expanded on and corroborated the sequence of landscape adjustment discussed here.

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  • Li, J., Gregory S. Okin, Lorelei Alvarez, and Howard Epstein. 2007. Quantitative effects of vegetation cover on wind erosion and soil nutrient loss in a desert grassland of southern New Mexico, USA. Biogeochemistry 85:317–332.

    DOI: 10.1007/s10533-007-9142-ySave Citation »Export Citation »E-mail Citation »

    Uses plots in which vegetation cover is experimentally manipulated to measure the effects of wind erosion on removal of soil particles and associated nutrient loss; nice discussion of how changes in vegetation cover influence wind erosion of soil.

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  • Marsh, G. P. 1865. Physical geography as modified by human action. New York: Charles Scribner.

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    Pioneering book on human effects on the environment, including how changes in land cover lead to accelerated soil erosion in uplands and sediment accumulation in lowlands; still worth reading more than a century after its publication; the classic, original treatise on environmental geology.

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  • Montgomery, D. R. 2007. Soil erosion and agricultural sustainability. Proceedings of the National Academy of Sciences of the United States of America 104:13,268–13,272.

    DOI: 10.1073/pnas.0611508104Save Citation »Export Citation »E-mail Citation »

    Data drawn from a global compilation of soil erosion studies indicate soil erosion rates one to two orders of magnitude higher in conventionally plowed croplands than in native land cover; documents the unsustainability of conventional agriculture in terms of soil fertility and contrasts this with much lower erosion rates for no-till agriculture.

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  • Ritchie, J. C., and J. R. McHenry. 1990. Application of radioactive fallout Cesium-137 for measuring soil erosion and sediment accumulation rates and patterns: A review. Journal of Environmental Quality 19:215–233.

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    Radioactive fallout isotopes facilitate measurement of multi-decadal rates of soil formation, erosion, and deposition; reviews use of Cs-137 for such studies, including case studies and limitations of the technique.

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  • Trimble, S. W. 2013. Historical agriculture and soil erosion in the Upper Mississippi Valley Hill Country. Boca Raton, FL: CRC.

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    Comprehensive account of the changes in land use that led to accelerated erosion of upland soils, deposition of sediment in stream channel networks, and continuing adjustments of channels, over many decades after land cover regrew, via alternating episodes of aggradation and incision.

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  • van Andel, T. H., E. Zangger, and A. Demitrack. 1990. Land use and soil erosion in prehistory and historical Greece. Journal of Field Archaeology 17:379–396.

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    Example of studies documenting accelerated upland soil erosion with the initial clearance of native land cover for agriculture, even if this clearance was done using simple tools more than a thousand years ago; uses sedimentary records from depositional sites such as river valleys to infer changes in land use and soil erosion.

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Subsidence refers to the collapse of surface materials into cavities created by removal of underlying material. Removal can occur with groundwater or oil and gas extraction; subsurface mining; compaction of organic rich soils that are drained for agriculture; or dissolution of naturally occurring minerals such as calcium carbonate or evaporite minerals, which are highly soluble under surface and near-surface conditions. Subsidence can occur in the absence of human activities, as when natural weathering dissolves calcium carbonate and creates caves. Subsidence can also be strongly exacerbated by human activities, as when irrigation of crops or urban landscaping increases water infiltration and accelerates dissolution of calcium carbonate. In some cases, subsidence starts with cracks in the ground surface rather than actual collapse of the ground surface into a subterranean cavity. The cracks can widen and deepen quickly, however, and create substantial problems for structures such as roads or buildings. Being able to detect, model, and predict future changes in land subsidence is useful in mitigating hazards associated with the subsidence, and a variety of techniques are used in this context. Amelung, et al. 1999 discusses the use of remote sensing techniques to monitor subsidence in Las Vegas, Nevada, over several years. Although much of the work on subsidence occurs in arid regions, Phien-wej, et al. 2006 provides an example of subsidence associated with groundwater pumping in a humid region in Thailand. Many urban areas in China also experience problems with subsidence, as reviewed in Hu, et al. 2004. Massonnet, et al. 1997 describes a slight variation on the theme of groundwater extraction by focusing on a geothermal field in which groundwater is extracted but then reinjected. Although 90 percent of the extracted water is reinjected, the site still experiences land subsidence. Galloway, et al. 1999 provides a well-illustrated national overview of subsidence in the United States. The majority of research on subsidence focuses on examples associated with groundwater extraction, and Galloway and Burbey 2011 provides a thorough overview of this issue.

  • Amelung, F., Devin L. Galloway, John W. Bell, Howard A. Zebker, and Randell J. Laczniak. 1999. Sensing the ups and downs of Las Vegas: InSAR reveals structural control of land subsidence and aquifer-system deformation. Geology 27:483–486.

    DOI: 10.1130/0091-7613(1999)027<0483:STUADO>2.3.CO;2Save Citation »Export Citation »E-mail Citation »

    Describes the use of space-borne radar to map changes in land subsidence over a period of several years; relates spatial extent and magnitude of subsidence to geologic factors such as location of faults and sediment composition and to human-caused factors such as water table.

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  • Galloway, D. L., and T. J. Burbey. 2011. Review: Regional land subsidence accompanying groundwater extraction. Hydrogeology Journal 19:1459–1486.

    DOI: 10.1007/s10040-011-0775-5Save Citation »Export Citation »E-mail Citation »

    Reviews ground-based and remote methods used to measure and map subsidence; measures used to slow or stop subsidence, including reduced groundwater withdrawal and recharge; and numerical models used to understand and predict subsidence.

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  • Galloway, D. L., D. R. Jones, and S. E. Ingebritsen, eds. 1999. Land subsidence in the United States. US Geological Survey Circular 1182. Reston, VA: US Geological Survey.

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    Comprehensive review of causes of land subsidence, including mining of groundwater, drainage of organic soils, and collapsing cavities, with numerous examples and spectacular photographs from across the United States.

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  • Hu, R. L., Z. Q. Yue, L. C. Wang, and S. J. Wang. 2004. Review on current status and challenging issues of land subsidence in China. Engineering Geology 76:65–77.

    DOI: 10.1016/j.enggeo.2004.06.006Save Citation »Export Citation »E-mail Citation »

    Land subsidence is a particularly important hazard in many urban areas of China, especially in coastal plain and delta regions, at the base of mountain ranges, and within alluvial basins between mountain ranges; this work provides a comprehensive overview of the locations and causes of subsidence in China.

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  • Massonnet, D., T. Holzer, and H. Vadon. 1997. Land subsidence caused by the East Mesa geothermal field, California, observed using SAR interferometry. Geophysical Research Letters 24:901–904.

    DOI: 10.1029/97GL00817Save Citation »Export Citation »E-mail Citation »

    Describes the use of spaceborne radar to characterize subsidence associated with the commercial development of a geothermal field in which groundwater is extracted and then reinjected.

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  • Phien-wej, N., P. H. Giao, and P. Nutalaya. 2006. Land subsidence in Bangkok, Thailand. Engineering Geology 82:187–201.

    DOI: 10.1016/j.enggeo.2005.10.004Save Citation »Export Citation »E-mail Citation »

    Describes land subsidence occurring as a result of deep-well pumping of groundwater over multiple decades; reviews results of numerical models used to predict subsidence and mitigation measures that limit continuing groundwater extraction.

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Forest scientists and silviculturalists work with characterizing, extracting, and regrowing commercial forests used to supply timber. Environmental geologists identify and mitigate the negative environmental effects on water and sediment associated with commercial or subsistence timber harvest. Timber harvest, particularly in the form of clear-cutting, has many effects on water chemistry and terrestrial and aquatic biota, but most environmental geology research focuses on the increased water yield that occurs in the years immediately after timber harvest and the increased sediment yields that can persist for more than a decade. Changes in water and sediment yield result from multiple effects during timber harvest, including removal of the forest canopy and associated interception and transpiration of water; changes in rainfall-runoff relations because of tree removal and compaction of soils by heavy machinery; decreased slope stability as a result of loss of interception and stabilization of sediment by plant roots; and decreased slope stability and increased sediment yield resulting from slope wash and gullying on unpaved roads constructed for forestry, as discussed in Madej 2001. The magnitude of these effects and the time required for the landscape to stabilize varies substantially between watersheds, as reviewed in Brown, et al. 2005. Griggs and Hein 1980 describes how excess sediment carried into the ocean also creates effects in the marine environment. Although much of the research on the effects of timber harvest comes from the Pacific Northwest region of North America, Ensign and Mallin 2001 provides a case study from a coastal plan swamp stream in North Carolina, United States. Aust and Blinn 2004 reviews research from the eastern United States and concludes that all of these negative environmental effects can be minimized if best management practices are applied during timber harvest. Rashin, et al. 2006 conducts a similar review for Washington State and finds that small streams are not necessarily protected by existing best management practices. Campbell and Doeg 1989 reviews existing studies in an Australian context and highlights gaps in research. An extensive literature documents all of these effects, and the works cited here are chosen primarily as examples representing many other papers. An environmental effect of timber harvest that has only recently begun to receive attention is the effects of timber harvest on carbon sequestration in biomass. Davis, et al. 2009 evaluates carbon sequestration in central Appalachian forests with differing harvest histories.

  • Aust, W. M., and C. R. Blinn. 2004. Forestry best management practices for timber harvesting and site preparation in the eastern United States: An overview of water quality and productivity research during the past 20 years (1982–2002). Water, Air, and Soil Pollution 4:5–36.

    DOI: 10.1023/B:WAFO.0000012828.33069.f6Save Citation »Export Citation »E-mail Citation »

    Review of numerous studies; timber harvest in steeper terrain results in increased slope erosion and sediment and nutrient yields to streams, but increases are within acceptable standards and water quality recovers in a few years if best management practices are used.

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  • Brown, A. E., L. Zhang, T. A. McMahon, A. W. Western, and R. A. Vertessy. 2005. A review of paired catchment studies for determining changes in water yield resulting from alterations in vegetation. Journal of Hydrology 310:28–61.

    DOI: 10.1016/j.jhydrol.2004.12.010Save Citation »Export Citation »E-mail Citation »

    Paired catchment studies involving deforestation, afforestation, regrowth, and forest conversion; time required for landscape to stabilize under changing forest cover varies substantially between sites and between different forms of vegetation alteration; low flows in streams tend to be more altered and for longer than peak flows.

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  • Campbell, I. C., and T. J. Doeg. 1989. Impact of timber harvesting and production on streams: A review. Marine and Freshwater Research 40:519–539.

    DOI: 10.1071/MF9890519Save Citation »Export Citation »E-mail Citation »

    Effects of timber harvest on water quality include elevated concentrations of dissolved salts, suspended solids, and nutrients, especially during peak flows; major effects on aquatic biota result from increased sediment inputs to streams or increased light through removal of riparian vegetation; emphasizes gaps in existing research, particularly with respect to Australia.

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  • Davis, S. C., A. E. Hessl, C. J. Scott, M. B. Adams, and R. B. Thomas. 2009. Forest carbon sequestration changes in response to timber harvest. Forest Ecology and Management 258:2101–2109.

    DOI: 10.1016/j.foreco.2009.08.009Save Citation »Export Citation »E-mail Citation »

    Compares the history of ecosystem carbon storage in central Appalachian watersheds with different histories of timber harvest; clear-cutting reduces carbon storage for decades and carbon sequestration during tree regrowth declines over time, resulting in lower long-term carbon storage than in selective cut or uncut forests.

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  • Ensign, S. H., and M. A. Mallin. 2001. Stream water quality changes following timber harvest in a coastal plain swamp forest. Water Research 35:3381–3390.

    DOI: 10.1016/S0043-1354(01)00060-4Save Citation »Export Citation »E-mail Citation »

    Timber harvest in a blackwater creek draining swamp forest in North Carolina resulted in significantly higher suspended solids, total nitrogen and phosphorus, fecal coliform bacteria, and significantly lower dissolved oxygen for more than a year relative to a similar creek without timber harvest; over longer periods, nuisance algal blooms occurred.

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  • Griggs, G. B., and J. R. Hein. 1980. Sources, dispersal, and clay mineral composition of fine-grained sediment off central and northern California. Journal of Geology 88:541–566.

    DOI: 10.1086/628543Save Citation »Export Citation »E-mail Citation »

    Discusses magnitude, sources, and offshore transport of fine-grained sediment reaching the ocean from rivers draining central and northern California; steep, unstable hillslopes, high rainfall, and timber harvest create substantial sediment yields from these catchments; suspended sediment is detectable in remote imagery for distances at least one hundred kilometers offshore.

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  • Madej, M. A. 2001. Erosion and sediment delivery following removal of forest roads. Earth Surface Processes and Landforms 26:175–190.

    DOI: 10.1002/1096-9837(200102)26:2<175::AID-ESP174>3.0.CO;2-NSave Citation »Export Citation »E-mail Citation »

    Reports effects on erosion and sediment yield of road removal efforts on abandoned logging roads in California; although such treatments do not completely eliminate erosion associated with forest roads, they substantially reduce this erosion.

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  • Rashin, E. B., C. J. Clishe, A. T. Loch, and J. M. Bell. 2006. Effectiveness of timber harvest practices for controlling sediment related water quality impacts. Journal of the American Water Resources Association 42:1307–1327.

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    Evaluates effects of best management practices in Washington State; stream buffers are effective at limiting sediment delivery to and physical disturbance of stream channels, but timber harvest negatively affected water quality of unbuffered small streams; discusses most effective practices and site conditions that minimize negative effects.

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Transportation Corridors

Construction and civil engineers are commonly in charge of locating and building transportation corridors such as roads and railroads, but environmental geologists identify and mitigate the negative environmental effects of these corridors on hillslopes, river corridors, and water and sediment dynamics. Among these effects are excess sediment from traction sand used in winter on paved roads, surface erosion on unpaved roads, and slope instability exacerbated by paved and unpaved roads. Larsen and Parks 1997 documents the effects of road proximity in increasing landslide frequency in Puerto Rico. Jones, et al. 2000 reviews the numerous interactions between stream networks and networks of unpaved roads in the Pacific Northwest region of North America. In addition to sediment, toxic materials including road salt wash from roads into streams, as reviewed in Kelly, et al. 2008 and Corsi, et al. 2010. Road-stream crossings such as bridges and culverts can create limits for downstream movement of sediment and upstream-downstream movements of aquatic organisms. These crossings can also be sources of sediment to downstream portions of the stream, as documented in Lane and Sheridan 2002. Roads and railroads within the river corridors can also create longitudinal damming associated with levees and raised embankments, thus limiting channel-floodplain connectivity, as discussed in Blanton and Marcus 2009. Bierman, et al. 2005 documents the utility of historical photographs in understanding diverse changes in land cover and environmental geologic processes, including the effects of interstate highway construction.

  • Bierman, P. R., J. Howe, E. Stanley-Mann, M. Peabody, J. Hilke, and C. A. Massey. 2005. Old images record landscape change through time. GSA Today 15:4–10.

    DOI: 10.1130/1052-5173(2005)015<4:OIRLCT>2.0.CO;2Save Citation »Export Citation »E-mail Citation »

    Illustrates the information that can be extracted from historical photographs with case studies from Vermont; examples of information include greater erosion in clear-cut than in partially or wholly forested sites, dramatic improvement in the quality of riparian buffers after 1980, and extensive topographic reconfiguration during construction of the first interstate highway in Vermont.

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  • Blanton, P., and W. A. Marcus. 2009. Railroads, roads and lateral disconnection in the river landscapes of the continental United States. Geomorphology 112:212–227.

    DOI: 10.1016/j.geomorph.2009.06.008Save Citation »Export Citation »E-mail Citation »

    Documents the geographic distribution of transportation corridors in alluvial floodplains of the United States and regional variability of the potential impacts of roads and railroads on lateral connectivity between channels and floodplains, as well as floodplain structure and function; impacts include crossings such as bridges and culverts and longitudinal damming associated with raised embankments.

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  • Corsi, S. R., D. J. Graczyk, S. W. Geis, N. L. Booth, and K. D. Richards. 2010. A fresh look at road salt: Aquatic toxicity and water-quality impacts on local, regional, and national scales. Environmental Science and Technology 44:7376–7382.

    DOI: 10.1021/es101333uSave Citation »Export Citation »E-mail Citation »

    Water quality analyses indicate aquatic toxicity of road salt during winter runoff periods; at many sites across the United States, concentrations exceed US Environmental Protection Agency acute and chronic water-quality criteria for aquatic life, particularly in northern regions of the country.

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  • Jones, J. A., F. J. Swanson, B. C. Wemple, and K. U. Snyder. 2000. Effects of roads on hydrology, geomorphology, and disturbance patches in stream networks. Conservation Biology 14:76–85.

    DOI: 10.1046/j.1523-1739.2000.99083.xSave Citation »Export Citation »E-mail Citation »

    Reviews different types of interactions between road and stream networks at the landscape scale; focuses on unpaved roads in mountainous forested terrain of the Pacific Northwest region of North America; develops a conceptual model of these interactions and uses it to examine ecosystem resilience.

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  • Kelly, V. R., G. M. Lovett, K. C. Weathers, et al. 2008. Long-term sodium chloride retention in a rural watershed: Legacy effects of road salt on streamwater concentration. Environmental Science and Toxicology 42:410–415.

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    Documents increases in sodium and chloride concentrations and export during 1985–2005 in a rural New York stream; increases largely occurred as a result of using road salt, but with a lag reflecting subsurface build-up of these salts; ecosystem functions can be altered at lower-than-lethal levels of these salts.

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  • Lane, P. N. J., and G. J. Sheridan. 2002. Impact of an unsealed forest road stream crossing: Water quality and sediment sources. Hydrological Processes 16:2599–2612.

    DOI: 10.1002/hyp.1050Save Citation »Export Citation »E-mail Citation »

    Example of on-site monitoring of local effects; construction of an unpaved road crossing introduced large amounts of sediment now deposited on the stream bed and created greater turbidity and total suspended solids downstream from the crossing during base flow conditions.

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  • Larsen, M. C., and J. E. Parks. 1997. How wide is a road? The association of roads and mass wasting in a forested montane environment. Earth Surface Processes and Landforms 22:835–848.

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    Used an extensive database of landslides in Puerto Rico to assess landslide frequency in relation to distance from a highway; at distances of eighty-five meters or less on either side of a highway, landslide frequency is five to eight times higher than in areas farther away from a highway.

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Civil and structural engineers and urban planners design, build, and maintain urban infrastructure. Environmental geology is among the disciplines that evaluate the effects of urbanization. Environmental geologists focus on potential effects on water and sediment dynamics, water quality, soil erosion, and hillslope stability. Investigations include characterizing the presence, rates, and magnitudes of these processes, and methods to minimize adverse effects. One of the first studies to document the effects of urbanization on water and sediment yields and stream channels is Wolman 1967. The basic patterns observed in this classic study include increased sediment yields to streams during construction and then substantially decreased sediment yields, with persistent increases in water yields and associated changes in stream form and function. These patterns have been reinforced by many subsequent studies in diverse urban environments, including Bledsoe and Watson 2001; Konrad, et al. 2005; and Grable and Harden 2006, each of which highlights the complexities of channel response to urbanization. Gurnell, et al. 2007 synthesizes many case studies in a review of urban effects on hydrology and rivers. Elmore and Kaushal 2008 documents the extensive burial of headwater streams within pipes in urban areas and discusses consequences for stream ecosystems. Gupta 2002 suggests geoindicators that can be used to assess the environmental effects of ongoing rapid urbanization in tropical and subtropical regions. Shuster and Highland 2007 reviews how urbanization on steep slopes increases risk from landslides, as well as discussing different measures that have been used to reduce landslide risk in urban areas.

  • Bledsoe, B. P., and C. C. Watson. 2001. Effects of urbanization on channel instability. Journal American Water Resources Association 37:255–270.

    DOI: 10.1111/j.1752-1688.2001.tb00966.xSave Citation »Export Citation »E-mail Citation »

    Example of a case study characterizing channel changes in response to urbanization; magnitude of changes in flow regime is sensitive to connectivity and conveyance of impervious areas as well as specific characteristics of receiving channels.

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  • Elmore, A. J., and S. S. Kaushal. 2008. Disappearing headwaters: Patterns of stream burial due to urbanization. Frontiers in Ecology and Environment 6:308–312.

    DOI: 10.1890/070101Save Citation »Export Citation »E-mail Citation »

    A significant number of small streams are buried in pipes as part of urbanization; given the documented importance of small streams to downstream portions of a river network, the loss of headwaters associated with stream burial has consequences for hydrology, water quality, and stream ecosystems.

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  • Grable, J. L., and C. P. Harden. 2006. Geomorphic response of an Appalachian valley and ridge stream to urbanization. Earth Surface Processes and Landforms 31:1707–1720.

    DOI: 10.1002/esp.1433Save Citation »Export Citation »E-mail Citation »

    Discusses deliberate changes such as channel realignment, channelization, bed and bank stabilization, and addition of coarse particles, and unintentional changes including changes in catchment water and sediment yields, and rainfall-runoff relations; channels primarily enlarge and bed grain size increases, but spatial patterns of erosion and deposition are complex.

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  • Gupta, A. 2002. Geoindicators for tropical urbanization. Environmental Geology 42:736–742.

    DOI: 10.1007/s00254-002-0551-xSave Citation »Export Citation »E-mail Citation »

    Rapidly increasing urban populations in developing countries of the tropics and subtropics highlight the need for assessment of associated environmental modifications; presents several geoindicators that can be used to measure impacts of urbanization; examples of geoindicators include flood intensity and magnitude, depletion and recharge of ground water, and water quality.

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  • Gurnell, A., M. Lee, and C. Souch. 2007. Urban rivers: Hydrology, geomorphology, ecology and opportunities for change. Geography Compass 1:1–20.

    DOI: 10.1111/j.1749-8198.2007.00058.xSave Citation »Export Citation »E-mail Citation »

    At the catchment scale, urban development transforms hydrological processes through increase of impervious surfaces and storm-water drainage; river water and sediment quality are affected by storm water and wastewater drainage and by point and diffuse pollutant sources; discusses channel engineering.

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  • Konrad, C. P., D. B. Booth, and S. J. Burges. 2005. Effects of urban development in the Puget Lowland, Washington, on interannual streamflow patterns: Consequences for channel form and streambed disturbance. Water Resources Research 41:W070009.

    DOI: 10.1029/2005WR004097Save Citation »Export Citation »E-mail Citation »

    Case study of the effects of urbanization on surface water hydrology; urbanization decreases interannual variability in annual maximum streamflow and duration of frequent high flows, but increases magnitude of frequent high flows.

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  • Shuster, R. L., and L. M. Highland. 2007. Urban landslides: Socioeconomic impacts and overview of mitigative strategies. Bulletin of Engineering Geology and the Environment 66:1–27.

    DOI: 10.1007/s10064-006-0080-zSave Citation »Export Citation »E-mail Citation »

    Discusses how development of hillslopes in urban areas increases the risk of rainfall or earthquakes triggering landslides; reviews approaches used to reduce risk.

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  • Wolman, M. G. 1967. A cycle of sedimentation and erosion in urban river channels. Geografiska Annaler 49A:385–395.

    DOI: 10.2307/520904Save Citation »Export Citation »E-mail Citation »

    A pioneering case study that was the first to document changing stability and geometry of channels in response to changes in the ratio of water and sediment yields entering channels as a result of changes in land cover, including deforestation, crops, grazing, and urbanization.

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Human uses of water resources create a variety of hazards to both human communities and natural ecosystems. The works cited here are subdivided into those concerned primarily with groundwater and those concerned primarily with surface water. This is an artificial distinction because human uses of water resources commonly create hazards that involve both surface and groundwater systems, which are of course coupled more or less closely. The basic types of hazards common to both ground and surface water are depletion of supplies through consumptive uses and contamination of water with a wide range of pollutants. Although ground and surface water are renewable resources, withdrawal of groundwater at rates faster than the groundwater is recharged is effectively a form of mining of water resources that have taken centuries to millennia to accumulate. Consumption of surface water at rates faster than replenishment by precipitation and groundwater results in numerous effects to downstream portions of the river network and the lake or nearshore marine environment off the mouth of the river. Contamination of ground and surface water can be effectively permanent on human timescales if the contaminants are highly persistent in the environment, such as radioactive materials, some trace elements, or some synthetic chemicals. Contamination can also be relatively transient, with ground or surface water able to recover through natural bioremediation once the input of a contaminant such as fecal coliform bacteria ceases. Other hazards associated with use of water resources are unique to either ground or surface water, such as ground subsidence associated with groundwater withdrawal or accelerated channel erosion downstream from dams that trap sediment.


Environmental geologists, hydrogeologists, and hydrologists all investigate different aspects of groundwater, and the areas of expertise and research focus of individuals from each of these disciplines commonly overlap substantially. Environmental geologists tend to investigate the location and volume of groundwater aquifers; rates and mechanisms of recharge of groundwater recharge, as discussed in Chowdhury, et al. 2010, as well as rates of depletion; pollution of aquifers, as discussed in the context of leaking underground fuel tanks in Shih, et al. 2004; and secondary effects of excessive groundwater withdrawal, such as subsidence, as documented in Teatini, et al. 2006. Ground water contamination can result from natural deposits that, when tapped by drinking-water wells, poison the population accessing this water. One of the most famous examples of such natural contamination comes from arsenic in drinking-water wells in Bangladesh, as reviewed in Ahmed, et al. 2002. Böhlke 2002 reviews how agriculture directly and indirectly affects groundwater quality and quantity. Konikow 2011 examines the intriguing idea that cumulative global groundwater depletion transfers mass to the oceans and is contributing to observed sea level rise. Voss, et al. 2013 describes a recently developed satellite-borne approach to quantifying groundwater volumes using gravity measurements in areas with restricted ground access or data availability. Wada, et al. 2010 estimates cumulative groundwater depletion rates during the past few decades.

  • Ahmed, K. M., P. Bhattacharya, M. A. Hasan, et al. 2002. Arsenic enrichment in groundwater of the alluvial aquifers in Bangladesh: An overview. Applied Geochemistry 19:181–200.

    DOI: 10.1016/j.apgeochem.2003.09.006Save Citation »Export Citation »E-mail Citation »

    Thorough review of the geochemistry of naturally occurring sources of arsenic that contaminate drinking-water wells in Bangladesh, including the processes that release arsenic compounds into the aquifer.

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  • Böhlke, J. K. 2002. Groundwater recharge and agricultural contamination. Hydrogeology Journal 10:153–179.

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    Reviews direct and indirect effects of agriculture on groundwater quantity and quality; direct effects include chemical contamination and hydrologic alterations; indirect effects include changes in rock-water reactions in soils and aquifers caused by altered chemistry of soil and water; discusses methods to mitigate negative effects.

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  • Chowdhury, A., M. K. Jha, and V. M. Chowdary. 2010. Delineation of groundwater recharge zones and identification of artificial recharge sites in West Medinipur district, West Bengal, using RS, GIS and MCDM techniques. Environmental Earth Sciences 59:1209–1222.

    DOI: 10.1007/s12665-009-0110-9Save Citation »Export Citation »E-mail Citation »

    Case study of different techniques that can be used to delineate and rank natural and artificial groundwater recharge sites for regions with depleted aquifers; suggested approach incorporates data on geology, surface morphology, and aquifer transmissivity.

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  • Konikow, L. F. 2011. Contribution of groundwater depletion since 1900 to sea-level rise. Geophysical Research Letters 38:L17401.

    DOI: 10.1029/2011GL048604Save Citation »Export Citation »E-mail Citation »

    Global overview of how groundwater depletion represents a transfer of mass from land to the oceans, which contributes to sea level rise; quantitative estimate derived from numerous forms of data suggests groundwater depletion of 4,500 cubic kilometers between 1900 and 2008, which equates to a sea level rise of 12.6 mm, or about 6 percent of the observed total.

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  • Shih, T., Y. Rong, T. Harmon, and M. Suffet. 2004. Evaluation of the impact of fuel hydrocarbons and oxygenates on groundwater resources. Environmental Science and Technology 38:42–48.

    DOI: 10.1021/es0304650Save Citation »Export Citation »E-mail Citation »

    Fuel additives such as methyl tert-butyl ether (MTBE) can enter and contaminate aquifers; examines the potential for groundwater contamination by such additives by characterizing their presence in groundwater beneath leaking underground fuel tanks, using data from over 7,200 monitoring wells in the Los Angeles area; MTBE poses the greatest problem.

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  • Teatini, P., M. Ferronato, G. Gambolati, and M. Gonella. 2006. Groundwater pumping and land subsidence in the Emilia-Romagna coastland, Italy: Modeling the past occurrence and the future trend. Water Resources Research 42:W01406.

    DOI: 10.1029/2005WR004242Save Citation »Export Citation »E-mail Citation »

    Documents subsidence associated with groundwater withdrawal since the early 1950s on the Italian coast; uses numerical models to reconstruct past subsidence and predict future rates and distribution; notes lag times in response associated with delayed compaction of clay aquitards between depleted aquifers.

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  • Voss, K. A., J. S. Famigletti, M. H. Lo, C. de Linage, M. Rodell, and S. C. Swenson. 2013. Groundwater depletion in the Middle East from GRACE with implications for transboundary water management in the Tigris-Euphrates-Western Iran region. Water Resources Research 49:904–914.

    DOI: 10.1002/wrcr.20078Save Citation »Export Citation »E-mail Citation »

    Uses observation from the Gravity Recovery and Climate Experiment (GRACE) satellite to quantitatively estimate groundwater storage based on measured gravity patterns; substantial depletion of groundwater between 2003 and 2009; intriguing example of spaceborne research in regions where data and ground access can be severely limited.

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  • Wada, Y., L. P. H. van Beek, C. M. van Kempen, J. W. T. M. Reckman, S. Vasak, and M. F. P. Bierkens. 2010. Global depletion of groundwater resources. Geophysical Research Letters 37:L20402.

    DOI: 10.1029/2010GL044571Save Citation »Export Citation »E-mail Citation »

    Global overview of groundwater depletion based on assessment of groundwater recharge using a global hydrological model and estimates of groundwater abstraction from diverse regions; analysis of subhumid to arid regions indicates depletion increased from 126 cubic kilometers in 1960 to 283 cubic kilometers in 2000.

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Surface Water

As in the case of groundwater, the expertise and research and management foci of environmental geologists overlap with those of hydrologists, civil engineers, and physical geographers in examining how diverse uses of surface water resources create hazards for human and natural communities. Primary hazards associated with surface water are depletion through consumptive use, pollution, and increased erosion or deposition associated with flow regulation by dams and diversions. One of the first steps in understanding depletion and storage is to quantify the geographic distribution of these alterations and relate them to stream flow patterns, as done for the United States in Graf 1999 and for major rivers around the world in Nilsson, et al. 2005. Vörösmarty and Sahagian 2000 synthesizes data on alteration of continental hydrologic processes by dams at global scales. Postel 1999 reviews the effects of irrigated agriculture on river systems around the world. Attempts to mitigate loss of ecosystem services on rivers affected by depletion through consumptive use and storage include experimental floods, as summarized for the Colorado River of North America in Andrews and Pizzi 2000 and in Mueller, et al. 2016. Environmental geologic research on pollution investigates the spatial extent, magnitude, and causes of pollution, as well as the physical and chemical processes that disperse or concentrate contaminants, as discussed for heavy metals in Ciszewski and Grygar 2016. River pollution is also addressed in a companion article in this Environmental Science article. Romano de Orte, et al. 2014 discusses an unusual form of pollution associated with mobilization of heavy metals in sediments via leakage of carbon dioxide injected into the subsurface as a means of carbon sequestration.

Energy use, Hazards, and Sustainability

As with other forms of natural resources, uses of energy sources can create hazards for human communities and diverse terrestrial, freshwater, and marine ecosystems. Environmental geology commonly includes those aspects of hazards related to changes in water and sediment dynamics and pollution of environmental media such as soil and water, including how these hazards and environmental impacts may limit the sustainable use of a particular energy source. The works cited here examine diverse environmental geology aspects of the use of coal, geothermal, hydroelectric and tidal, and oil and natural gas as sources of energy.


Sedimentary geologists and mining engineers investigate the geographic distribution, volume, and energy potential of coal-bearing rock units, as well as the technology that can be used to access these deposits. Environmental geologists focus on how to minimize adverse secondary effects from coal mining, including altered topography, processes and rates of erosion and deposition, and contamination of soil and ground and surface waters. Contamination can result from excess sediment deposition or from toxic substances released by mining or combusting coal. Adriano, et al. 1980 discusses the problems associated with disposal of coal residues left from combustion. Bian, et al. 2009 evaluates the potential of different coal mining wastes to contaminate soil, groundwater, and surface water when the wastes are used as fill-in areas with subsidence problems. Tiwary 2001 reviews different environmental hazards from acid-mine drainage and nonacidic drainage from coal mines. Coal can have experienced relatively low temperatures and pressures underground and thus occur in the form of lignite or other forms of coal with relatively low energy potential and substantial levels of toxic chemicals such as sulfur compounds. Coal can also occur as anthracite that has experienced high temperatures and pressures, resulting in a form of coal with high energy potential and lower levels of potential contaminants. Coal can be mined underground or strip-mined at the surface by removing overlying layers. Strip mining can result in massive removal of overlying vegetation, soil, and rock units, particularly as practiced in so-called mountaintop removal. Palmer, et al. 2010 reviews the varied environmental damage associated with this form of coal mining. Rathore and Wright 1993 discusses how different types of remotely sensed data can be used to monitor surface mining effects that extend over enormous areas, evolve rapidly through time, and occur on lands that may have limited ground access. Bell, et al. 1989 critically reviews the effectiveness of legally mandated mined land reclamation to approximate original contour. Zipper, et al. 1989 and Martin-Duque, et al. 2010 describe alternative models for reclamation of steep slopes after mining.

  • Adriano, D. C., A. L. Page, A. A. Elseewi, A. C. Chang, and I. Straughan. 1980. Utilization and disposal of fly ash and other coal residues in terrestrial ecosystems: A review. Journal of Environmental Quality 9:333–344.

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    Coal residues contain potentially hazardous substances and are difficult to dispose of safely; reviews physical and chemical properties of coal ash as a function of the coal’s geological origin, combustion conditions, efficiency of particulate removal, and weathering before final disposal.

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  • Bell, J. C., W. L. Daniels, and C. E. Zipper. 1989. The practice of “approximate original contour” in the central Appalachians: I. Slope stability and erosion potential. Landscape and Urban Planning 18:127–138.

    DOI: 10.1016/0169-2046(89)90004-2Save Citation »Export Citation »E-mail Citation »

    The 1977 Surface Mining Control and Reclamation Act in the United States mandated that mining sites be stabilized and returned to approximate original contour as part of reclamation; evaluates long-term slope stability and potential erosivity of central Appalachian landforms restored in this way; major problems result from improper hill configurations, seepage, and inaccurate estimation of geotechnical parameters.

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  • Bian, Z., J. Dong, S. Lei, H. Leng, S. Mu, and H. Wang. 2009. The impact of disposal and treatment of coal mining wastes on environment and farmland. Environmental Geology 58:625–634.

    DOI: 10.1007/s00254-008-1537-0Save Citation »Export Citation »E-mail Citation »

    Since the 1980s, increasing use in China of coal mining wastes as fill-in areas with subsidence problems; evaluates the components of coal mining wastes and their potential to contaminate soil, surface water, and groundwater.

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  • Martin-Duque, J. F., M. A. Sanz, J. M. Bodoque, A. Lucia, and C. Martin-Moreno. 2010. Restoring earth surface processes through landform design: A 13-year monitoring of a geomorphic reclamation model for quarries on slopes. Earth Surface Processes and Landforms 35:531–548.

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    Discusses challenges to reclamation of contour mining and quarries on slopes; challenges include steep slopes prone to mass movement and water erosion; presents highwall-trench-concave slope approach to reclamation, which does not reproduce approximate original contour, but allows continued erosional adjustment of steep slopes and stabilization and soil formation along the base of the slopes.

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  • Palmer, M. A., E. S. Bernhardt, W. H. Schlesinger, et al. 2010. Mountaintop mining consequences. Science 327:148–149.

    DOI: 10.1126/science.1180543Save Citation »Export Citation »E-mail Citation »

    Surface mining is now the dominant driver of land-use change in the central Appalachian region of the United States; one form of surface mining, known as mountaintop mining with valley fills, is particularly environmentally damaging, as reviewed in this article.

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  • Rathore, C. S., and R. Wright. 1993. Monitoring environmental impacts of surface coal mining. International Journal of Remote Sensing 14:1021–1042.

    DOI: 10.1080/01431169308904394Save Citation »Export Citation »E-mail Citation »

    Coal mining covers extensive areas but access may be limited by mining companies; discusses use of satellite and airborne remote imagery to map and assess effects of surface mining.

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  • Tiwary, R. K. 2001. Environmental impact of coal mining on water regime and its management. Water, Air, and Soil Pollution 132:185–199.

    DOI: 10.1023/A:1012083519667Save Citation »Export Citation »E-mail Citation »

    Discharge of huge amounts of mine water that may be acidic or neutral is one environmental effect of coal mining; acid-mine drainage has been the subject of extensive research but nonacidic mine waters can have high total suspended solids, dissolved solids, and heavy metals.

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  • Zipper, C. E., W. L. Daniels, and J. C. Bell. 1989. The practice of “approximate original contour” in the central Appalachians: II. Economic and environmental consequences of an alternative. Landscape and Urban Planning 18:139–152.

    DOI: 10.1016/0169-2046(89)90005-4Save Citation »Export Citation »E-mail Citation »

    Evaluates alternatives to use of approximate original contour (AOC) in mined land reclamation and finds that alternatives are cheaper and more effective, indicating that, although AOC improved on earlier methods, additional improvements are still possible.

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Geothermal energy is the energy contained as heat within Earth’s interior. Much of the research on geothermal energy focuses on characterizing and developing geothermal energy resources, although Majer and Peterson 2007 is an example of investigation of associated hazards; in this case, injection-induced seismicity. Yousefi, et al. 2010 provides an example of mapping geothermal energy sources using diverse types of geological data. Geothermal sources can be very shallow and have relatively low energy potential, as discussed in Allen and Milenic 2003. Deeper geothermal sources can be vapor-dominated, hot water, geopressured, hot dry rock, and magma, as reviewed in Gupta and Roy 2007 and, with more attention to hydrology and chemistry of geothermal fluids, in Glassley 2015. Zaigham and Nayyar 2010 discusses the potential for geothermal energy development from deep, hot dry rock in Pakistan. Barbier 2002 reviews heat transfer mechanisms within Earth and the characteristics of geothermal fields as well as methods for developing geothermal resources. Angelis-Dimakis, et al. 2011 reviews several forms of alternative energy sources, including geothermal.

  • Allen, A., and D. Milenic. 2003. Low-enthalpy geothermal energy resources from groundwater in fluvioglacial gravels of buried valleys. Applied Energy 74:9–19.

    DOI: 10.1016/S0306-2619(02)00126-5Save Citation »Export Citation »E-mail Citation »

    Enthalpy is a measure of energy in a thermodynamic system; low-enthalpy geothermal energy can be generated from groundwater in gravels filling buried Pleistocene glacial valleys that underlie contemporary floodplains in river flowing through large cities; cities elevate temperatures in shallow groundwater, which can be used for space-heating buildings by passing the water through a heat pump.

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  • Angelis-Dimakis, A., M. Biberacher, J. Dominguez, et al. 2011. Methods and tools to evaluate the availability of renewable energy sources. Renewable and Sustainable Energy Reviews 15:1182–1200.

    DOI: 10.1016/j.rser.2010.09.049Save Citation »Export Citation »E-mail Citation »

    Reviews methods and tools available to determine exploitable renewable energy from solar, wind, waves, biomass, and geothermal sources; discusses challenges for each renewable energy source.

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  • Barbier, E. 2002. Geothermal energy technology and current status: An overview. Renewable and Sustainable Energy Reviews 6:3–65.

    DOI: 10.1016/S1364-0321(02)00002-3Save Citation »Export Citation »E-mail Citation »

    Thorough review of Earth’s internal structure, heat transfer mechanisms within the different layers of Earth, locations and types of geothermal fields, and methods of exploration for and development of geothermal resources.

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  • Glassley, W. E. 2015. Geothermal energy. 2d ed. Boca Raton, FL: CRC.

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    A comprehensive overview similar to that in Gupta and Roy 2007, with more attention to the hydrology and chemistry of geothermal fluids.

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  • Gupta, H., and S. Roy. 2007. Geothermal energy: An alternative resource for the 21st century. Amsterdam: Elsevier.

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    Covers basic concepts of Earth structure and heat transfer; types of geothermal systems, which include vapor-dominated, hot water, geopressured, hot dry rock, and magma; exploration techniques such as geochemical, geophysical, and airborne surveys using aeromagnetic, remote sensing, and infrared detection; and assessment and exploitation of geothermal sources.

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  • Majer, E. L., and J. E. Peterson. 2007. The impact of injection on seismicity at The Geysers, California Geothermal Field. International Journal of Rock Mechanics and Mining Sciences 44:1079–1090.

    DOI: 10.1016/j.ijrmms.2007.07.023Save Citation »Export Citation »E-mail Citation »

    Water injection into geothermal systems is used to extend geothermal production but can result in enhanced seismic activity; observed seismicity in this case study is predictable, suggesting that carefully controlled injection can be used safely.

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  • Yousefi, H., Y. Noorollahi, S. Ehara, et al. 2010. Developing the geothermal resources map of Iran. Geothermics 39:140–151.

    DOI: 10.1016/j.geothermics.2009.11.001Save Citation »Export Citation »E-mail Citation »

    Geothermal exploration is financially risky because of a high degree of uncertainty; describes a method for geothermal exploration and resource identification based on use of geological, geochemical, and geophysical data; constructs a map of geothermal resources in Iran as an example.

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  • Zaigham, N. A., and Z. A. Nayyar. 2010. Renewable hot dry rock geothermal energy source and its potential in Pakistan. Renewable and Sustainable Energy Reviews 14:1124–1129.

    DOI: 10.1016/j.rser.2009.10.002Save Citation »Export Citation »E-mail Citation »

    Hot dry rocks at greater depths than hydro-geothermal resources are widespread in Pakistan, including immediately below some of the nation’s urban-industrial centers, as indicated by satellite temperature data and borehole measurements of temperature that indicate high geothermal gradients.

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Hydroelectric and Tidal

Hydroelectric and tidal energy sources are sometimes regarded as clean sources of energy because they do not create hydrocarbon emissions, but they do create environmental impacts. Only minimal effort has gone into using tidal energy sources, but hydroelectric energy from river flow has been extensively developed throughout Europe and North America, and is now being rapidly developed elsewhere. Jackson, et al. 2005 provides an example of the analysis that environmental geologists undertake to characterize tidal energy and coastal morphology. Rourke, et al. 2010 reviews the technological development of tidal energy, as well as the technical and environmental limitations to expanded use. Among the environmental limitations are public acceptance, potential impacts on marine wildlife, and disruption of sand transport. Frid, et al. 2012 addresses impacts to marine wildlife, and Neill, et al. 2012 investigates the disruption of sand dynamics. An extensive body of literature demonstrates that hydroelectric dams alter physical, chemical, and biological features of river corridors and impoverish biodiversity and ecosystem services in affected rivers, as explored in more detail in a companion article in this article. It is possible to develop hydroelectric energy in a manner less devastating to river ecosystems, but this has not been a priority. Hydroelectric and tidal energy projects are sited and developed by engineers. Environmental geologists investigate the effects of these projects on surficial geology processes as well as how to minimize some of the negative effects. One proposed alternative to enormous hydroelectric projects is development of distributed, micro hydro projects that generate less than about twenty-five megawatts of energy. Micro hydro is widely spoken of as being less environmentally disruptive, although Abbasi and Abbasi 2011 questions the basis for this belief, not least because micro hydro power plants, like larger power plants, require a reservoir and penstock to create an artificial waterhead and extract the potential energy of water flowing downhill via suitable turbomachinery. The loss of longitudinal connectivity for organisms and sediment associated with these structures can be reduced where micro hydro is sited on a small, secondary channel rather than the main channel, but this practice is not always followed. Another approach is to use river current energy conversion systems in which a river turbine is used to generate energy without ponding water, as explained in Khan, et al. 2008. Khan, et al. 2009 reviews potential uses of this type of energy generation in both tidal and river settings: in tidal settings, hydrokinetic energy conversion systems may create less environmental disruption than energy generation that relies on a tidal barrage in which stored potential energy of a tidal basin is harnessed.

  • Abbasi, T., and S. A. Abbasi. 2011. Small hydro and the environmental implications of its extensive utilization. Renewable and Sustainable Energy Reviews 15:2134–2143.

    DOI: 10.1016/j.rser.2010.11.050Save Citation »Export Citation »E-mail Citation »

    Critically examines the claim that small hydropower systems have fewer adverse environmental impacts than large hydropower systems; widespread use of small systems is likely to cause equal environmental damage on per-unit-energy basis; discusses ways to mitigate the damages associated with small hydropower systems.

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  • Frid, C., E. Andonegi, J. Depestele, et al. 2012. The environmental interactions of tidal and wave energy generation devices. Environmental Impact Assessment Review 32:133–139.

    DOI: 10.1016/j.eiar.2011.06.002Save Citation »Export Citation »E-mail Citation »

    Notes lack of scientific information that can be used in evaluating benefits and potential environmental costs of alternative offshore energy developments other than wind power; discusses pros and cons of tidal barrages and offshore tidal stream energy and wave energy collectors with differing designs.

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  • Jackson, D. W. T., J. A. G. Cooper, and L. del Rio. 2005. Geological control of beach morphodynamic state. Marine Geology 216:297–314.

    DOI: 10.1016/j.margeo.2005.02.021Save Citation »Export Citation »E-mail Citation »

    Examines beaches in Northern Ireland along an environmental gradient with respect to tidal and wave energy and finds that existing parameters for describing the three-dimensional morphology of the beaches are not very accurate; discusses factors that control beach morphology.

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  • Khan, M. J., G. Bhuyan, M. T. Iqbal, and J. E. Quaicoe. 2009. Hydrokinetic energy conversion systems and assessment of horizontal and vertical axis turbines for river and tidal applications: A technology status review. Applied Energy 86:1823–1835.

    DOI: 10.1016/j.apenergy.2009.02.017Save Citation »Export Citation »E-mail Citation »

    Reviews and evaluates existing and proposed schemes for converting river kinetic energy to usable power; discusses existing limitations, research gaps, and obstacles to wider implementation of these systems.

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  • Khan, M. J., M. T. Iqbal, and J. E. Quaicoe. 2008. River current energy conversion systems: Progress, prospects and challenges. Renewable and Sustainable Energy Reviews 12:2177–2193.

    DOI: 10.1016/j.rser.2007.04.016Save Citation »Export Citation »E-mail Citation »

    River current energy conversion systems are electromechanical energy converters that convert river kinetic energy to other forms of energy; reviews current technology and challenges to implementing these systems.

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  • Neill, S. P., J. R. Jordan, and S. J. Couch. 2012. Impact of tidal energy converter (TEC) arrays on the dynamics of headland sand banks. Renewable Energy 37:387–397.

    DOI: 10.1016/j.renene.2011.07.003Save Citation »Export Citation »E-mail Citation »

    Numerical model of how large-scale exploitation of tidal energy could alter nearshore sediment dynamics; examines potential effects of such exploitation on sand banks formed by large eddies generated by strong tidal flow past headlands; these sand banks help to protect coasts from erosion.

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  • Rourke, F. O., F. Boyle, and A. Reynolds. 2010. Tidal energy update 2009. Applied Energy 87:398–409.

    DOI: 10.1016/j.apenergy.2009.08.014Save Citation »Export Citation »E-mail Citation »

    Reviews pros and cons of different techniques used to exploit tidal energy since construction of the first large tidal barrage in 1967; tidal current turbines are less environmentally damaging than tidal barrages but are not yet economically viable on a large scale.

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Oil and Natural Gas

Sedimentary geologists work to identify, map, and develop oil and natural gas deposits. Environmental geologists document the negative effects of oil and gas extraction on soil; ground and surface water quality and quantity; and contaminant dispersal via wind, water, and adsorption to sediment, as well as how to minimize environmental hazards associated with these processes. A relatively recent environmental hazard associated with oil and gas extraction is the occurrence of injection-induced seismicity, which is addressed in this article under Earthquakes. Gregory, et al. 2011 provides an overview of the challenges of dealing with contaminated water produced by hydraulic fracturing, and Osborn, et al. 2011 documents methane contamination of groundwater aquifers as a result of hydraulic fracturing during natural gas extraction. Nadim, et al. 2000 discusses methods used to detect and remediate petroleum contamination of water and soil. Eberts, et al. 2012 describes the use of environmental tracers to model the vulnerability of ground water supplies to contamination. Durell, et al. 2006 provides an example of using diverse indicators to monitor and model contaminant dispersal associated with drilling in a marine environment. Although not specific to oil and gas development, Ridgway and Shimmield 2002 provides a nice example of how environmental geologic understanding of erosional and depositional processes can inform understanding of contaminant dispersal. Aelion 1996 exemplifies studies that use geological properties of environmental media, in this case grain size and stratigraphy within an aquifer, to understand patterns of contaminant dispersal. Brusseau 1994 provides an overview of understanding of contaminant transport in heterogeneous porous media, such as sediment and many types of bedrock.

  • Aelion, C. M. 1996. Impact of aquifer sediment grain size on petroleum hydrocarbon distribution and biodegradation. Journal of Contaminant Hydrology 22:109–121.

    DOI: 10.1016/0169-7722(95)00080-1Save Citation »Export Citation »E-mail Citation »

    Investigates aquifer in South Carolina contaminated by jet fuel spill in 1975; jet fuel concentration correlated with clay content of the aquifer sediment; biodegradation of jet fuel constituents was less in clay-rich sediments than in sandy sediments, likely contributing to the higher contaminant concentrations.

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  • Brusseau, M. L. 1994. Transport of reactive contaminants in heterogeneous porous media. Reviews of Geophysics 32:285–313.

    DOI: 10.1029/94RG00624Save Citation »Export Citation »E-mail Citation »

    Thorough review of the transport and fate of contaminants in subsurface systems, as investigated using theoretical, experimental, and mathematical modeling as well as limited field experiments; discusses major factors controlling contaminant transport as well as additional research needs.

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  • Durell, G., T. R. Utvik, S. Johnsen, T. Frost, and J. Neff. 2006. Oil well produced water discharges to the North Sea. Part I: Comparison of deployed mussels (Mytilus edulis), semi-permeable membrane devices, and the DREAM model predictions to estimate the dispersion of polycyclic aromatic hydrocarbons. Marine Environmental Research 62:194–223.

    DOI: 10.1016/j.marenvres.2006.03.013Save Citation »Export Citation »E-mail Citation »

    Reports on more than a decade of monitoring of produced water discharges from North Sea oil wells; monitoring data have been used to develop and validate a dispersion model for polycyclic aromatic hydrocarbons (PAHs); predictions using different monitoring techniques agree well and indicate that factors such as tidally mediated fluctuations in PAH concentrations in surface water affect monitoring results.

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  • Eberts, S. M., J. K. Böhlke, L. J. Kauffman, and B. C. Jurgens. 2012. Comparison of particle-tracking and lumped-parameter age-distribution models for evaluating vulnerability of production wells to contamination. Hydrogeology Journal 20:263–282.

    DOI: 10.1007/s10040-011-0810-6Save Citation »Export Citation »E-mail Citation »

    Example of the complexities of understanding how changing nonpoint-source contaminant inputs affect groundwater, which partly depends on the distribution of groundwater ages; compares age distributions derived from different methods for four sites; both methods yielded roughly similar age distributions.

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  • Gregory, K. B., R. D. Vidic, and D. A. Dzombak. 2011. Water management challenges associated with the production of shale gas by hydraulic fracturing. Elements 7:181–186.

    DOI: 10.2113/gselements.7.3.181Save Citation »Export Citation »E-mail Citation »

    Useful review of issues of water management associated with development of unconventional, onshore natural gas resources in deep shale where hydraulic fracturing is used; a primary issue is how to contain or treat large volumes of water with high concentrations of solutes that return to the surface following fracturing.

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  • Nadim, F., G. E. Hoag, S. Liu, R. J. Carley, and P. Zack. 2000. Detection and remediation of soil and aquifer systems contaminated with petroleum products: An overview. Journal of Petroleum Science and Engineering 26:169–178.

    DOI: 10.1016/S0920-4105(00)00031-0Save Citation »Export Citation »E-mail Citation »

    Remediation of sites contaminated with organic chemicals is relatively new; nice review of routes of soil and groundwater contamination with petroleum hydrocarbons and remediation techniques, as well as results of toxicological studies on petroleum hydrocarbons and suggested next steps for protecting ground water from such contamination.

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  • Osborn, S. G., A. Vengosh, N. R. Warner, and R. B. Jackson. 2011. Methane contamination of drinking water accompanying gas-well drilling and hydraulic fracturing. Proceedings of the National Academy of Science of the United States of America 108:8172–8176.

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    Example of study documenting methane contamination of groundwater, in this case aquifers overlying shale formations in Pennsylvania and New York, as a result of shale-gas extraction; methane concentrations in drinking-water wells close to active drilling sites posed a potential explosion hazard.

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  • Ridgway, J., and G. Shimmield. 2002. Estuaries as repositories of historical contamination and their impact on shelf seas. Estuarine, Coastal and Shelf Science 55:903–928.

    DOI: 10.1006/ecss.2002.1035Save Citation »Export Citation »E-mail Citation »

    Estuaries are sinks for sediment and adsorbed contaminants, ecologically important features, and sites of industrial and urban development; useful overview of distribution, concentration, controlling influences on, and impacts of, estuarine contamination from diverse sites; contaminants in most estuaries remain in the coastal zone, but contaminants from major Chinese rivers disperse hundreds of kilometers across the continental shelf.

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Waste Disposal and Contaminant Dispersal

Although many of the works cited already in this article address some aspect of waste disposal and contaminant dispersal, this portion of the article focuses on processes or types of contaminants not explicitly addressed, including atmospheric deposition as a process and excess nutrients, radioactive waste, synthetic chemicals, and trace elements as types of contaminants. As with other aspects of environmental contamination, environmental geologists contribute detailed knowledge of geologic transport processes and reactions of contaminants with environmental media, including surface water and groundwater and diverse types of sediments.

Atmospheric Deposition

Atmospheric deposition can occur as wet deposition of material falling with precipitation in the form of rain or snow. Dry atmospheric deposition involves material falling in the absence of precipitation. Environmental geologists use geochemical and sedimentary characteristics to investigate the sources of the material being deposited, as discussed in Reynolds, et al. 2006 and Goudie 2009. Environmental geologists also work with atmospheric scientists to understand atmospheric transport pathways and with ecotoxicologists to understand effects of contaminant deposition on biotic communities. Although a variety of materials can be transported atmospherically, those receiving the most attention include dust, mercury, and nitrates. Dust refers to wind-transported silt and clay particles that both directly contain minerals such as iron but also adsorb other chemicals such as sulfur dioxide, as thoroughly reviewed in Goudie and Middleton 2006. Dust can cause adverse environmental effects such as more rapid melting of snowpacks and glaciers, asthma and other illnesses in people, and excess nutrients in marine environments such as coral reefs, as discussed in Shinn, et al. 2000. Dust can also have beneficial effects such as sustaining soil productivity, as documented in Chadwick, et al. 1999. Depositional environments including river floodplains and deltas, lakes, and ocean basins contain sedimentary records of fluctuations in atmospheric deposition over varying timescales. Neff, et al. 2008 uses lake sediment cores to document how human activities have increased dust deposition in the western United States. Glacial ice also records fluctuations in atmospheric deposition, as discussed in Schuster, et al. 2002 for mercury. Environmental geologist use knowledge of erosional and depositional processes in diverse surface and near-surface environments to investigate how materials deposited from the atmosphere are dispersed or concentrated in soil and water. Nitrates are nutrients, and elevated rates of atmospheric deposition of nitrates can be detected by comparing contemporary depositional rates to geologic records such as lake sediments, as discussed for the western United States in Fenn, et al. 2003.

  • Chadwick, O. A., L. A. Derry, P. M. Vitousek, B. J. Huebert, and L. O. Hedlin. 1999. Changing sources of nutrients during four million years of ecosystem development. Nature 397:491–497.

    DOI: 10.1038/17276Save Citation »Export Citation »E-mail Citation »

    Soil development in humid regions should result in nutrient depletion as rock-derived elements are gradually lost, but atmospheric inputs of nutrients can sustain soil productivity, as demonstrated here for highly weathered soils in Hawaiian rainforests, which are supplied with cations from the ocean and phosphorus in dust from central Asia.

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  • Fenn, M. E., J. S. Baron, E. B. Allen. 2003. Ecological effects of nitrogen deposition in the western United States. BioScience 53:404–420.

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    Western United States generally receives low levels of atmospheric nitrogen inputs, but sites downwind from large metropolitan areas or agricultural operations receive elevated levels; aquatic and terrestrial ecosystems at these sites can be altered by nitrogen deposition.

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  • Goudie, A. S. 2009. Dust storms: Recent developments. Journal of Environmental Management 90:89–94.

    DOI: 10.1016/j.jenvman.2008.07.007Save Citation »Export Citation »E-mail Citation »

    Thorough overview of effects of dust storms on the environment and human health; progress in identifying source areas for dust storms, including recognition of the Sahara and western China as the strongest global dust sources; and recognition of variations in dust storm activity over wide-ranging time scales.

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  • Goudie, A. S., and N. J. Middleton. 2006. Desert dust in the global system. Berlin: Springer.

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    Comprehensive treatment of sources of dust, human acceleration of surface erosion and atmospheric transport of dust, and effects of dust deposition on widely spread environments.

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  • Neff, J. C., A. P. Ballantyne, G. L. Farmer, et al. 2008. Increasing eolian dust deposition in the western United States linked to human activity. Nature Geoscience 1:189–195.

    DOI: 10.1038/ngeo133Save Citation »Export Citation »E-mail Citation »

    Uses lake sediments to determine accumulation rates and geochemical properties of atmospheric dust inputs; European settlement of the western United States caused dust inputs to increase by 500 percent above the late Holocene average as a result of livestock grazing, agriculture, and other land uses.

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  • Reynolds, R., J. Neff, M. Reheis, and P. Lamothe. 2006. Atmospheric dust in modern soil on aeolian sandstone, Colorado Plateau (USA): Variation with landscape position and contribution to potential plant nutrients. Geoderma 130:108–123.

    DOI: 10.1016/j.geoderma.2005.01.012Save Citation »Export Citation »E-mail Citation »

    Uses magnetic and mineral properties to distinguish the contributions of soil nutrients derived from local bedrock versus atmospheric dust from distant locations; wind-blown dust contributes 40–80 percent of the nutrient stocks in the uppermost soil layers at sites undisturbed by land uses.

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  • Schuster, P. F., D. P. Krabbenhoff, D. L. Naftz, et al. 2002. Atmospheric mercury deposition during the last 270 years: A glacial ice core record of natural and anthropogenic sources. Environmental Science and Technology 36:2303–2310.

    DOI: 10.1021/es0157503Save Citation »Export Citation »E-mail Citation »

    Atmospheric mercury transport is primary mechanism of mercury contamination at regional to global scales; glacial ice cores from Wyoming indicate anthropogenic sources contribute about half of the mercury, with most of the rest from background sources, although proportion of anthropogenic inputs has increased significantly during the 20th century.

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  • Shinn, E. A., G. W. Smith, J. M. Prospero, et al. 2000. African dust and the demise of Caribbean coral reefs. Geophysical Research Letters 27:3029–3032.

    DOI: 10.1029/2000GL011599Save Citation »Export Citation »E-mail Citation »

    Caribbean coral reefs have declined since the late 1970s, which coincides with large increases in transatlantic dust transport; dust includes excess nutrients and provides a substrate for spores of soil fungi that can infect corals.

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Excess Nutrients

Nutrients such as nitrogen and phosphorus are critical for living organisms. Diverse human activities, however, tend to concentrate nutrients in levels greater than necessary for the survival of individual organisms or ecosystems. Excess nutrients can result in eutrophication of surface waters such as lakes and rivers. Eutrophication is the depletion of dissolved oxygen within the water, which kills aquatic animals. Eutrophication commonly occurs when high concentrations of nutrients lead to increases in algae and other plants. As the plants die, bacterial degradation of their biomass depletes dissolved oxygen in the water. Environmental geologists focus on understanding the sources of nitrogen, as exemplified in Holloway and Dahlgren 1999, as well as the physical mechanisms of nutrient dispersal, deposition, and bioavailability in near-surface environments including groundwater, soils, and surface waters. Goolsby, et al. 2000 discusses sources and transport of nitrogen that causes eutrophication in the Gulf of Mexico. Ye, et al. 2012 models dissolved nitrate dynamics in a river network. McKergow, et al. 2003 documents the effects of riparian zones in retaining sediment nutrients in a small Australian river basin. Chen, et al. 2007 discusses geologic controls on nitrate dispersal in groundwater. Kim, et al. 2003 investigates the effects of sediment characteristics on phosphorus dynamics in river and lake sediments. Environmental geologists also use geological records such as sediment deposits to document changes in nutrient levels through time, as illustrated by study of nitrogen levels in lake sediments in Wolfe, et al. 2001. Anderson, et al. 1993 explains how diatom fossils in cores of lake sediments can be used to infer changes in phosphorus concentration through time.

  • Anderson, N. J., B. Rippey, and C. E. Gibson. 1993. A comparison of sedimentary and diatom-inferred phosphorus profiles: Implications for defining pre-disturbance nutrient conditions. Hydrobiologia 253:357–366.

    DOI: 10.1007/BF00050761Save Citation »Export Citation »E-mail Citation »

    Use observed correlations between diatom assemblages and phosphorus load in lakes of Northern Ireland to infer phosphorus concentration changes through time based on diatoms in lake sediment cores; direct measurement of phosphorus in sediments has more uncertainty because of postdepositional transformations of phosphorus.

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  • Chen, J., M. Taniguchi, G. Liu, K. Miyaoka, S. Onodera, and T. Tokunaga. 2007. Nitrate pollution of groundwater in the Yellow River delta, China. Hydrogeology Journal 15:1605–1614.

    DOI: 10.1007/s10040-007-0196-7Save Citation »Export Citation »E-mail Citation »

    Example of using field surveys to map spatial distribution of nitrate in groundwater as well as nitrate sources; nitrate occurred mainly in shallow groundwater and corresponded to irrigated agriculture and anthropogenic waste.

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  • Goolsby, D. A., W. A. Battaglin, B. T. Aulenbach, and R. P. Hooper. 2000. Nitrogen input to the Gulf of Mexico. Journal of Environmental Quality 30:329–336.

    DOI: 10.2134/jeq2001.302329xSave Citation »Export Citation »E-mail Citation »

    Used historical river discharge and nitrogen concentrate data in statistical models to estimate the annual flux of nitrogen to the Gulf of Mexico and to identify primary sources of nitrogen in the Mississippi River basin; interannual variations in nitrogen flux result from variations in precipitation and discharge; principal sources are Midwestern agricultural lands.

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  • Holloway, J. M., and R. A. Dahlgren. 1999. Geologic nitrogen in terrestrial biogeochemical cycling. Geology 27:567–570.

    DOI: 10.1130/0091-7613(1999)027<0567:GNITBC>2.3.CO;2Save Citation »Export Citation »E-mail Citation »

    Case study; nitrogen from bedrock released during weathering and soil formation accounts for 30 to 50 percent of total soil nitrogen in study area; more nitrogen available than required by biota, so nitrate leaching contributes to elevated nitrate concentrations in stream water.

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  • Kim, L. H., E. Choi, and M. K. Stenstrom. 2003. Sediment characteristics, phosphorus types and phosphorus release rates between river and lake sediments. Chemosphere 50:53–61.

    DOI: 10.1016/S0045-6535(02)00310-7Save Citation »Export Citation »E-mail Citation »

    Case study; measures phosphorus release from bottom sediments of tributaries to the Han River, Korea, and investigates chemistry of minerals involved and rates of phosphorus release relative to water-quality standards.

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  • McKergow, L. A., D. M. Weaver, I. P. Prosser, R. B. Grayson, and A. E. G. Reed. 2003. Before and after riparian management: Sediment and nutrient exports from a small agricultural catchment, Western Australia. Journal of Hydrology 270:253–272.

    DOI: 10.1016/S0022-1694(02)00286-XSave Citation »Export Citation »E-mail Citation »

    Case study assessing effectiveness of restored native riparian vegetation in trapping sediment and nutrients; sediment transport decreased by an order of magnitude because of reduced bank erosion; the form of phosphorus being exported changed, but nitrogen export changed negligibly.

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  • Wolfe, A. P., J. S. Baron, and R. J. Cornett. 2001. Anthropogenic nitrogen deposition induces rapid ecological changes in alpine lakes of the Colorado Front Range (USA). Journal of Paleolimnology 25:1–7.

    DOI: 10.1023/A:1008129509322Save Citation »Export Citation »E-mail Citation »

    Lake sediment cores record marked enhanced atmospheric deposition of nitrogen from agricultural and industrial sources since c. 1950; rate and magnitude of associated changes in lake ecology far exceed natural variability as indicated by fourteen-thousand-year sediment records from the lake.

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  • Ye, S., T. P. Covino, M. Sivapalan, N. B. Basu, H. Y. Li, and S. W. Wang. 2012. Dissolved nutrient retention dynamics in river networks: A modelling investigation of transient flows and scale effects. Water Resources Research 48:W00J17.

    DOI: 10.1029/2011WR010508Save Citation »Export Citation »E-mail Citation »

    Use numerical models to simulate catchment-scale retention of dissolved nutrients during transient flow pulses; evaluated different scenarios; results suggest that relative efficiencies and processes of nutrient retention vary substantially, but generally decrease with more variability in stream flow.

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Radioactive Waste

Nuclear power is a clean energy source in the context of fossil fuel emissions, but the containment of radioactive material during operation of the power plant and disposal of radioactive spent fuel and contaminated materials from the power plant pose severe environmental hazards. Siting of waste disposal requires knowledge of site geology, partly because of the extremely long time spans for which disposal sites are supposed to remain stable, and partly because of the need to understand potential contaminant dispersal pathways via geologic transport in water and soil. Environmental geologists thus participate in the planning of radioactive waste disposal sites and in understanding the rates and mechanisms of environmental dispersal of contaminants that are not properly isolated and contained. An example of planning for disposal comes from Yucca Mountain, Nevada, which was proposed as the national high-level radioactive waste repository for the United States. Long and Ewing 2004 reviews potential geologic hazards at the site, which include volcanic eruptions and groundwater contamination. Connor, et al. 2000 documents evaluation of potential hazards associated with volcanic eruptions at the site. Flint, et al. 2001 reviews the extensive groundwater research that has been conducted at the site. Stunning examples of 20th-century irresponsible disposal of radioactive materials come from the Los Alamos National Laboratory in the United States, nuclear facilities in Siberia, and nuclear-powered submarines abandoned in the Arctic Ocean by the former Soviet Union. Graf 1994 provides a thorough account of plutonium dispersal downstream from Los Alamos. Kenna and Sayles 2002 reconstructs the history of radioactive contamination as a result of nuclear weapons development using sediment cores from the Ob River in Siberia. Nies, et al. 1999 documents dispersal of nuclear pollutants in the Arctic Ocean. Although it remains unclear whether sunken nuclear submarines will be a major source of radioactive contamination in the Arctic Ocean, Matishov, et al. 2002 documents elevated levels of radioactive isotopes in Arctic Ocean sediments as a result of long-range atmospheric transport from European nuclear reprocessing facilities and from nuclear accidents such as Chernobyl.

  • Connor, C. B., J. A. Stamatakos, D. A. Ferrill, et al. 2000. Geologic factors controlling patterns of small-volume basaltic volcanism: Application to a volcanic hazards assessment at Yucca Mountain, Nevada. Journal of Geophysical Research Solid Earth 105:417–432.

    DOI: 10.1029/1999JB900353Save Citation »Export Citation »E-mail Citation »

    Example of a natural hazard study undertaken in connection with Yucca Mountain as a high-level radioactive waste repository; examined volcanic hazards at regional and local scales based on geologic records of tectonic movement and volcanic eruptions and geophysical imaging of the subsurface, along with numerical modeling of crustal structure and stability.

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  • Flint, A. L., L. E. Flint, G. S. Bodvarsson, E. M. Kwicklis, and J. Fabryka-Martin. 2001. Evolution of the conceptual model of unsaturated zone hydrology at Yucca Mountain, Nevada. Journal of Hydrology 247:1–30.

    DOI: 10.1016/S0022-1694(01)00358-4Save Citation »Export Citation »E-mail Citation »

    Example of a study of the hydrologically related hazards at Yucca Mountain; examined infiltration and groundwater dynamics using field measurements, numerical modeling, and borehole data on isotopic ratios of groundwater and matrix characteristics; traces evolution of research methods and understanding of the site over the preceding two decades.

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  • Graf, W. L. 1994. Plutonium and the Rio Grande: Environmental change and contamination in the Nuclear Age. New York: Oxford Univ. Press.

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    Comprehensive account of the history of nuclear weapons research at Los Alamos National Laboratory in New Mexico; the related release of plutonium into tributaries of the Rio Grande; and the subsequent dispersal of plutonium within the river network.

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  • Kenna, T. C., and F. L. Sayles. 2002. The distribution and history of nuclear weapons related contamination in sediments from the Ob River, Siberia as determined by isotopic ratios of plutonium and neptunium. Journal of Environmental Radioactivity 60:105–137.

    DOI: 10.1016/S0265-931X(01)00099-6Save Citation »Export Citation »E-mail Citation »

    Radioactive isotopes in sediment cores from five locations along the Ob River record inputs from nuclear weapons facilities in Siberia during the second half of the 20th century; contaminants from at least two sources have been transported along the length of the Ob River, but global fallout from atmospheric weapons test is the dominant source of radioactivity.

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  • Long, J. C. S., and R. C. Ewing. 2004. Yucca Mountain: Earth-science issues at a geologic repository for high-level nuclear waste. Annual Review of Earth and Planetary Sciences 32:363–401.

    DOI: 10.1146/annurev.earth.32.092203.122444Save Citation »Export Citation »E-mail Citation »

    Reviews environmental geology issues associated with use of Yucca Mountain as a radioactive waste repository; issues include water infiltrating the repository, corroding waste containment canisters, dissolving the waste, and transporting the waste into areas accessible by biota; area around Yucca Mountain is seismically and volcanically active.

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  • Matishov, G. G., D. G. Matishov, A. E. Namjatov, J. N. Smith, J. L. Carroll, and S. Dahle. 2002. Radioactivity near the sunken submarine “Kursk” in the Southern Barents Sea. Environmental Science and Technology 36:1919–1922.

    DOI: 10.1021/es0112487Save Citation »Export Citation »E-mail Citation »

    Measured radioactivity in water, sediment, and biota around an abandoned Russian nuclear submarine sunken in the Arctic Ocean; levels of radioactivity match background levels from global fallout, the Chernobyl accident, and discharge from European nuclear fuel reprocessing facilities; interannual fluctuations recorded in sediment reflect discharge from European facilities, which are the major contributor of radioactivity in the area.

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  • Nies, H., I. H. Harms, M. J. Karcher, D. Dethleff, and C. Bahe. 1999. Anthropogenic radioactivity in the Arctic Ocean—review of the results from the joint German project. Science of the Total Environment 237–238:181–191.

    DOI: 10.1016/S0048-9697(99)00134-5Save Citation »Export Citation »E-mail Citation »

    Evaluates continuing effects of past dumping of nuclear wastes in Arctic Ocean; sampled water, marine sediment, and sea ice; combined data with numerical models of pathways and dispersion of radioactive isotopes; sea ice rapidly transports contaminated sediments from Arctic into Atlantic Ocean via the East Greenland Current.

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Synthetic Chemicals

Synthetic chemicals here refers to chemical compounds created in laboratories for specific industrial purposes or compounds created as inadvertent by-products of processes such as fossil fuel combustion. Categories of synthetic chemicals include organochlorine compounds such as pesticides; volatile organic compounds such as industrial solvents; polycyclic aromatic hydrocarbons (PAHs) that are by-products of fossil fuel combustion that can move freely between water and air phases; and polychlorinated biphenyls (PCBs) used as insulating or cooling agents, among other purposes. Environmental geologists use knowledge of near-surface transport pathways and geochemical reactions to investigate the dispersal and concentration of synthetic chemicals via wind, water, ice, and movement of sediments to which the chemicals are adsorbed. Senesi 1992 reviews knowledge of how soil properties influence binding of organochlorine pesticides to soil particles. Gevao, et al. 1997 documents changes in PCB concentrations in lake sediments as a result of varying levels of PCB production and post-depositional mobility of PCBs. The evidence of recycling of PCBs between lake sediment and lake water is particularly troubling, given that PCBs are so toxic that their manufacture has been banned for decades. Manoli and Samara 1999 reviews sources and dispersion of PAHs in surface water and groundwater. Wurl and Obbard 2005 documents levels of multiple synthetic chemicals in nearshore sediments around Singapore, and Hong, et al. 2008 examines patterns of organochlorine sediments in shallow marine sediments in the coastal environment of Vietnam. Wang, et al. 2006 uses patterns of organochlorine pesticides in soils to investigate the effects of pesticide use and soil processes on spatial distribution of pesticides.

  • Gevao, B., H. Hamilton-Taylor, C. Murdoch, K. C. Jones, M. Kelly, and B. J. Tabner. 1997. Depositional time trends and remobilization of PCBs in lake sediments. Environmental Science and Technology 31:3274–3280.

    DOI: 10.1021/es970276fSave Citation »Export Citation »E-mail Citation »

    Vertical concentration of PCBs in lake sediment at a site in the United Kingdom agrees well with published production data of PCBs in the United Kingdom, but provides evidence for postdepositional mobility of PCBs, suggesting recycling of PCBs between the sediment and the overlying water.

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  • Hong, S. H., U. H. Yim, W. J. Shim, J. R. Oh, P. H. Viet, and P. S. Park. 2008. Persistent organochlorine residues in estuarine and marine sediments from Ha Long Bay, Hai Phong Bay, and B Lat Estuary, Vietnam. Chemosphere 72:1193–1202.

    DOI: 10.1016/j.chemosphere.2008.02.051Save Citation »Export Citation »E-mail Citation »

    Organochlorine compounds found to be widely distributed in sediments of the northeastern coastal environment of Vietnam; concentrations and type of contaminants correlate with shipping and industrial activities; levels of dichloro-diphenyl-trichloroethane (DDT) compounds exceed guidelines from other countries.

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  • Manoli, E., and C. Samara. 1999. Polycyclic aromatic hydrocarbons in natural waters: Sources, occurrence and analysis. Trends in Analytical Chemistry 18:417–428.

    DOI: 10.1016/S0165-9936(99)00111-9Save Citation »Export Citation »E-mail Citation »

    Overview of how PAHs are introduced to surface water and groundwater from point and nonpoint sources, concentrations and frequency of occurrence in diverse aqueous samples, and capabilities of analytical techniques and requirements for achieving reliable analyses of PAHs.

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  • Senesi, N. 1992. Binding mechanisms of pesticides to soil humic substances. Science of the Total Environment 123–124:63–76.

    DOI: 10.1016/0048-9697(92)90133-DSave Citation »Export Citation »E-mail Citation »

    Review of the nature of forces binding pesticides to soils and the types of mechanisms involved in the adsorption of pesticides to soil humic material; includes experimental evidence of adsorption processes.

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  • Wang, X., X. Piao, J. Chen, J. Hu, F. Xu, and S. Tao. 2006. Organochlorine pesticides in soil profiles from Tianjin, China. Chemosphere 64:1514–1520.

    DOI: 10.1016/j.chemosphere.2005.12.052Save Citation »Export Citation »E-mail Citation »

    Example of a study using soil cores to investigate causes in vertical fluctuations in concentrations; soil profiles indicate that application of pesticides is the major contributor of these contaminants, rather than sources such as wastewater; pesticide concentrations decline with depth, except where plowing and irrigation create higher concentrations at depth.

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  • Wurl, O., and J. P. Obbard. 2005. Organochlorine pesticides, polychlorinated biphenyls and polybrominated diphenyl ethers in Singapore’s coastal marine sediments. Chemosphere 58:925–933.

    DOI: 10.1016/j.chemosphere.2004.09.054Save Citation »Export Citation »E-mail Citation »

    Persistent organic pollutants (POPs) are ubiquitous, persistent, and toxic, creating increasing concern over their global distribution; this work is an example of using marine sediment samples to characterize the distribution and concentrations of POPs, which are concentrated around industrial areas with intensive shipping traffic in this study of Singapore.

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Trace Elements

Trace elements occur naturally in the environment, but human activities can change the concentration and location of trace elements. Many trace elements are essential to human health and the health of organisms. Some trace elements are very toxic at even low concentrations, whereas some essential trace elements are toxic at elevated concentrations, as reviewed in Presley 2005. Among the most commonly studied trace elements are arsenic, cadmium, chromium, copper, lead, mercury, nickel, selenium, and zinc. Environmental geologists investigate sources of trace elements as well as the processes that transport them, deposit and concentrate them, and chemically alter the trace elements with effects on bioavailability. Koinig, et al. 2003 uses a core of lake sediments to document changes in trace element deposition resulting from natural and anthropogenic processes. Singh, et al. 2005 uses sediment samples from an Indian river to investigate trace metal inputs and redistribution through time. Papadopoulou-Vrynioti, et al. 2013 investigates how geomorphic characteristics such as transport distance and mechanism, and grain-size distribution, influence the distribution of trace elements in river sediments. Ndjigui, et al. 2008 provides an example of analyzing how bedrock composition and weathering processes result in enrichment or depletion of specific trace elements. Gaillardet, et al. 2003 provides a thorough review of trace elements in river waters.

  • Gaillardet, J., J. Viers, and B. Dupre. 2003. Trace elements in river waters. In Treatise on geochemistry. Edited by J. I. Drever, 225–272. San Diego, CA: Academic Press.

    DOI: 10.1016/B0-08-043751-6/05165-3Save Citation »Export Citation »E-mail Citation »

    Comprehensive review of natural and anthropogenic sources of trace elements in river waters, global patterns of trace elements in river waters, and methods of detecting and measuring trace elements.

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  • Koinig, K. A., W. Shotyk, A. F. Lotter, C. Ohlendorf, and M. Sturm. 2003. 9000 years of geochemical evolution of lithogenic major and trace elements in the sediment of an alpine lake—the role of climate, vegetation, and land-use history. Journal of Paleolimnology 30:307–320.

    DOI: 10.1023/A:1026080712312Save Citation »Export Citation »E-mail Citation »

    Mineralogy, grain size, pollen, macrofossils, and geochemistry of a sediment core from a Swiss lake indicate that changes in vegetation, which reflect changes in climate and land use, drive changes in trace element deposition in the lake because vegetation acts to stabilize soils containing these trace elements.

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  • Ndjigui, P. D., P. Bilong, D. Bitom, and A. Dia. 2008. Mobilization and redistribution of major and trace elements in two weathering profiles developed on serpentinites in the Lomié ultramafic complex, south-east Cameroon. Journal of African Earth Sciences 50:305–328.

    DOI: 10.1016/j.jafrearsci.2007.10.006Save Citation »Export Citation »E-mail Citation »

    Case study of how bedrock lithology and weathering processes influence the environmental availability of trace elements; weathering of bedrock into sediment results in depletion of some elements and enrichment of others.

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  • Papadopoulou-Vrynioti, K., D. Alexakis, G. D. Bathrellos, et al. 2013. Distribution of trace elements in stream sediments of Arta plain (western Hellas): The influence of geomorphological parameters. Journal of Geochemical Exploration 134:17–26.

    DOI: 10.1016/j.gexplo.2013.07.007Save Citation »Export Citation »E-mail Citation »

    Sediment samples from several rivers in Greece suggest both geological and human influences on trace element content; rock type and catchment topography influence the release of trace elements to rivers, as do land uses such as farming.

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  • Presley, B. J. 2005. Trace element pollution. Water encyclopedia 4:109–113.

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    Thorough review of how to measure trace elements, how diverse human activities mobilize and concentrate trace elements, and environmental regulations on trace elements.

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  • Singh, K. P., D. Mohan, V. K. Singh, and A. Malik. 2005. Studies on the distribution and fractionation of heavy metals in Gomti River sediments – a tributary of the Ganges, India. Journal of Hydrology 312:14–27.

    DOI: 10.1016/j.jhydrol.2005.01.021Save Citation »Export Citation »E-mail Citation »

    Example of a spatially extensive analysis of the types and concentrations of trace elements in a particular environmental setting – here, a tributary of the Ganges River; the distribution of trace elements in river sediments includes sites where concentrations pose high risks to humans and other biota.

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The Global Carbon Cycle

As people have become increasingly concerned about rising levels of atmospheric carbon dioxide, scientists from diverse disciplines have sought to quantify the various components of the carbon cycle, including quantities of carbon stored in rocks, soil, vegetation, and surface water and groundwater as well as the atmosphere, and the fluxes of carbon among these reservoirs. As with other forms of storage and flux, environmental geologists contribute the perspective of geological time scales and sedimentary and ice records of past conditions; geological processes including rock uplift, weathering, erosion, and deposition of sediment; knowledge of rates and magnitudes of natural processes that sequester carbon in depositional environments including soils, floodplains, wetlands, lakes, deltas, and ocean basins; and insight into how human activities change patterns and quantities of carbon emission, transport, and sequestration. The works cited here include examples of how geological and anthropogenic processes release organic carbon stored in geologic environments and examples of how geological and anthropogenic processes store carbon in diverse environments.

Organic Carbon Emissions

Some of the works cited here explore how geological processes influence rates of carbon dioxide release to the atmosphere versus sequestration by burial in marine sediments over long timescales. Raymo and Ruddiman 1992 initiated this type of research by suggesting that uplift of the Himalayan plateau and associated changes in silicate weathering rates altered atmospheric carbon dioxide concentrations and triggered global cooling and the formation of continental ice sheets. Galy, et al. 2007 expands on this idea with more recent quantifications of carbon dynamics from the Himalaya to deposition on the Bengal Fan. Gaillardet and Galy 2008 explains the processes that influence the balance between mountain uplift and erosion as a source versus sink of atmospheric carbon dioxide over millions of years. Other works cited here explore environmental geologic influences on carbon emissions at much shorter timescales. Tranvik, et al. 2009 reviews mechanisms of carbon emission and burial from lakes and reservoirs, and explains how the cumulative influence of processes in these smaller water bodies exceeds that of processes in the ocean. Gudasz, et al. 2010 explores the temperature dependence of carbon dynamics in lakes and predicts greater carbon emissions from freshwater as air temperatures warm. Sutfin, et al. 2016 discusses the storage of organic carbon along river corridors in the form of downed wood and floodplain soils and explains how human alteration of river process and form reduces this storage and increases atmospheric carbon emissions. Hanberry, et al. 2015 provides a striking example of these changes for the lower Mississippi River alluvial valley, where human alterations have reduced organic carbon storage by 98 percent relative to prehistoric levels. Rooney, et al. 2012 discusses substantial losses of carbon storage via destruction of boreal peatlands in connection with open-pit mining of oil sands in northern Canada.

  • Gaillardet, J., and A. Galy. 2008. Himalaya—carbon sink or source? Science 320:1727–1728.

    DOI: 10.1126/science.1159279Save Citation »Export Citation »E-mail Citation »

    Mountain ranges have diverse effects on global carbon dynamics and can act as a net source of atmospheric carbon dioxide via oxidation of sedimentary or fossil organic carbon and carbon dioxide outgassing, or a net sink via rock weathering and burial of organic matter.

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  • Galy, V., C. France-Lanord, O. Beyssac, P. Faure, H. Kudrass, and F. Palhol. 2007. Efficient organic carbon burial in the Bengal fan sustained by the Himalayan erosional system. Nature 450:407–410.

    DOI: 10.1038/nature06273Save Citation »Export Citation »E-mail Citation »

    Examines mechanics of how continental erosion controls atmospheric carbon dioxide levels over geological timescales via silicate weathering, and river transport and oceanic burial of carbon in sediment; develops a carbon budget for the Himalayan erosional system from the mountains to burial in the Bengal fan; high uplift rates equate to efficient ocean burial of carbon.

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  • Gudasz, C., D. Bastviken, K. Steger, K. Premke, S. Sobek, and L. J. Tranvik. 2010. Temperature-controlled organic carbon mineralization in lake sediment. Nature 466:478–481.

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    Organic carbon deposited with lake sediment can be buried over geological time scales or mineralized and taken up by biota or released to the atmosphere; mineralization increases with water temperature, suggesting that warming climate will result in less carbon sequestration in boreal lake sediments.

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  • Hanberry, B. B., J. M. Kabrick, and H. S. He. 2015. Potential tree and soil carbon storage in a major historical floodplain forest with disrupted ecological function. Perspectives in Plant Ecology, Evolution and Systematics 17:17–23.

    DOI: 10.1016/j.ppees.2014.12.002Save Citation »Export Citation »E-mail Citation »

    Case study from the lower Mississippi River alluvial valley; quantitatively estimates organic carbon storage in riparian vegetation biomass and floodplain soil; infers historical levels of these quantities and measures contemporary levels; current carbon storage is about 2 percent of historical levels as a result of deforestation and floodplain drainage.

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  • Raymo, M. E., and W. F. Ruddiman. 1992. Tectonic forcing of late Cenozoic climate. Nature 359:117–122.

    DOI: 10.1038/359117a0Save Citation »Export Citation »E-mail Citation »

    Influential paper on how tectonic uplift of the Tibetan plateau could have caused global cooling and the growth of continental ice sheets during the Cenozoic Era, leading to increases in chemical weathering of silicate rocks that resulted in decreased atmospheric carbon dioxide concentrations over the past forty million years.

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  • Rooney, R., S. E. Bayley, and D. W. Schindler. 2012. Oil sands mining and reclamation cause massive loss of peatland and stored carbon. Proceedings National Academy of Sciences of the United States of America 109:4933–4937.

    DOI: 10.1073/pnas.1117693108Save Citation »Export Citation »E-mail Citation »

    Boreal peatlands store disproportionately large quantities of organic carbon relative to their spatial extent; disruption of boreal peatlands during open-pit mining of oil sands in Canada is releasing enormous quantities of stored carbon that will not be restored when the land cover is allowed to regrow as upland forest.

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  • Sutfin, N. A., E. E. Wohl, and K. A. Dwire. 2016. Banking carbon: A review of organic carbon storage and physical factors influencing retention in floodplains and riparian ecosystems. Earth Surface Processes and Landforms 41:38–60.

    DOI: 10.1002/esp.3857Save Citation »Export Citation »E-mail Citation »

    Comprehensive review of the factors that influence organic carbon storage in downed wood and sediment along river corridors; synthesizes quantitative estimates of this storage from diverse regions; explores how human modification of river corridors, including floodplain drainage and deforestation, reduces carbon storage along rivers.

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  • Tranvik, L. J., J. A. Downing, J. B. Cotner, et al. 2009. Lakes and reservoirs as regulators of carbon cycling and climate. Limnology and Oceanography 54:2298–2314.

    DOI: 10.4319/lo.2009.54.6_part_2.2298Save Citation »Export Citation »E-mail Citation »

    Thorough review of the mechanisms regulating carbon storage and emissions in lakes; estimates that global emissions of carbon dioxide from lakes are similar in magnitude to carbon dioxide uptake by oceans and that burial of carbon in lake sediments exceeds that in oceans.

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Organic Carbon Transport and Sequestration

Scientists started to develop global budgets of organic carbon a few decades ago. As these efforts progressed, a mystery developed as it quickly became clear that the atmosphere was not retaining all of the carbon dioxide being released into by human activities such as combustion of fossil fuels. Where was the carbon going—into the oceans or the land? As different terms in the carbon budget were quantified with increasing certainty, scientists began to refer to the missing terrestrial carbon sink. Some portion(s) of the terrestrial biosphere was absorbing substantial amounts of carbon. Attention focused on environments such as the tropical rainforests or the extensive boreal forests of North America and Eurasia, all of which have substantial biomass and associated carbon. With time, however, soils have been recognized to be the single-largest terrestrial reservoir of organic carbon. Some types of soils store disproportionately large amounts of carbon relative to their geographic extent, as demonstrated on a global scale for northern permafrost soils in Tarnocai, et al. 2009, and on a local scale for floodplain soils in mountainous river catchments of the Southern Rockies in Wohl, et al. 2012. The stability of carbon stored in soil is also of concern. Terrestrial carbon mobilized by soil erosion travels adsorbed to fine sediment particles, so that river-suspended sediment transport and carbon fluxes correlate. Holmes, et al. 2002 reports on historical records of sediment flux from large Arctic rivers and notes the difficulties of interpreting multi-decadal patterns from inconsistent records. Soil carbon transported by Canada’s Mackenzie River is being released by thawing permafrost as climate warms, and Hilton, et al. 2015 documents a mean age of 5,800 years for this carbon. Hilton, et al. 2008b investigates transport of carbon derived from erosion of vegetation and soil via landslides during a cyclone in Taiwan. The researchers find that most of the transport occurs during cyclonic floods. Some of the carbon transported by rivers is deposited in floodplains and stored for hundreds to thousands of years. Hoffmann, et al. 2009 is the first study to quantitatively estimate the amount of carbon stored across a large river basin. Leithold, et al. 2016 explores how differences in plate tectonic setting and river basin size influence the speed of carbon transport between terrestrial sources and marine depositional sites. Sedimentary bedrock can also contain fossil organic carbon that can be released through weathering and erosion. Hilton, et al. 2008a examines the mix of fossil carbon and carbon derived from soils and vegetation that is transported to the ocean by rivers draining the western South Alps of New Zealand.

  • Hilton, R. G., A. Galy, and N. Hovius. 2008a. Riverine particulate organic carbon from an active mountain belt: Importance of landslides. Global Biogeochemical Cycles 22

    DOI: 10.1029/2006GB002905Save Citation »Export Citation »E-mail Citation »

    Landslides in New Zealand transport a mix of fossil carbon from bedrock and carbon from soils and vegetation; nonfossil carbon constitutes about 63 percent of the total carbon in the suspended sediment load of rivers draining the western Southern Alps of New Zealand; burial of this sediment sequesters atmospherically derived carbon.

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  • Hilton, R. G., A. Galy, N. Hovius, M. C. Chen, M. J. Horng, and H. Chen. 2008b. Tropical-cyclone-driven erosion of the terrestrial biosphere from mountains. Nature Geoscience 1:759–762.

    DOI: 10.1038/ngeo333Save Citation »Export Citation »E-mail Citation »

    More than a third of global carbon flux to the oceans comes from rivers draining mountains in the western Pacific region, where tropical cyclones generate floods that carry the great majority of this carbon to marine depositional sites.

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  • Hilton, R. G., V. Galy, J. Gaillardet, et al. 2015. Erosion of organic carbon in the Arctic as a geological carbon dioxide sink. Nature 524:84–87.

    DOI: 10.1038/nature14653Save Citation »Export Citation »E-mail Citation »

    Soils in the northern high latitudes store approximately twice as much carbon as the atmosphere, but warming and permafrost thawing can expose this soil carbon to erosion, release it to the atmosphere, and transport it in rivers; sampling indicates Canada’s Mackenzie River transports carbon with a mean age of 5,800 years.

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  • Hoffmann, T., S. Glatzel, and R. Dikau. 2009. A carbon storage perspective on alluvial sediment storage in the Rhine catchment. Geomorphology 108:127–137.

    DOI: 10.1016/j.geomorph.2007.11.015Save Citation »Export Citation »E-mail Citation »

    Quantifies carbon storage in floodplain soils of the Rhine River catchment; suggests that approximately equal amounts of carbon are being exported via river transport and stored in floodplain soil.

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  • Holmes, R. M., J. W. McClelland, B. J. Peterson, I. A. Shiklomanov, A. I. Shiklomanov, et al. 2002. A circumpolar perspective on fluvial sediment flux to the Arctic Ocean. Global Biogeochemical Cycles 16:1098.

    DOI: 10.1029/2001GB001849Save Citation »Export Citation »E-mail Citation »

    Carbon transport by rivers correlates with suspended sediment transport; this work presents a pan-arctic synthesis of sediment flux from nineteen arctic rivers; interannual variations in sediment flux are large and inconsistencies in historical measurements and reporting create challenges for accurately quantifying sediment fluxes.

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  • Leithold, E. L., N. E. Blair, and K. W. Wegmann. 2016. Source-to-sink sedimentary systems and global carbon burial: A river runs through it. Earth-Science Reviews 153:30–42.

    DOI: 10.1016/j.earscirev.2015.10.011Save Citation »Export Citation »E-mail Citation »

    Carbon buried in marine sediments reflects differences in the contributing river basin; large rivers on tectonically passive plate margins have extensive floodplains and much of the carbon in transport is taken up by biota or released to the atmosphere; small, mountainous river basins along tectonically active margins is rapidly transported from terrestrial source areas to marine burial sites.

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  • Tarnocai, C., J. G. Canadell, E. A. G. Schuur, P. Kuhry, G. Mazhitova, and S. Zimov. 2009. Soil organic carbon pools in the northern circumpolar permafrost region. Global Biogeochemical Cycles 23:GB2023.

    DOI: 10.1029/2008GB003327Save Citation »Export Citation »E-mail Citation »

    Soils contain the largest terrestrial reservoir of organic carbon; permafrost, or permanently frozen ground, in the northern circumpolar region stores a disproportionately large portion of this carbon; northern permafrost covers 16 percent of the global soil area but stores an estimated 50 percent of the global soil organic carbon.

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  • Wohl, E., K. Dwire, N. Sutfin, L. Polvi, and R. Bazan. 2012. Mechanisms of carbon storage in mountainous headwater rivers. Nature Communications 3:1263.

    DOI: 10.1038/ncomms2274Save Citation »Export Citation »E-mail Citation »

    Quantifies organic carbon storage in downed wood and floodplain sediment along mountain rivers and identifies spatial heterogeneities in storage; relatively wide, low-gradient segments of the river network, which constitute a small portion of total river length, store nearly three-quarters of the organic carbon in the river network.

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The Anthropocene

The concept of an Anthropocene era of time that is designated based on extensive human alteration of Earth’s surface and near-surface environments has been discussed for several decades. The idea only began to gain widespread acceptance and use, however, when Crutzen 2002 proposed it as a formal epoch of geological time. The appropriate arbiters within the geological sciences community—the International Commission on Stratigraphy or the International Union of Geological Sciences—have not yet officially approved or defined the term as of 2016, but acceptance is likely to come within the following years. Crutzen is an atmospheric chemist, and he proposed designation of an Anthropocene epoch based on human influence on Earth’s atmosphere. The works cited here discuss multiple lines of evidence that indicate pervasive and intensifying human alteration of all aspects of Earth’s surface and near-surface environments that form part of the subject matter of environmental geology. Hooke 2000 is one of the first geological works to argue that people now move more sediment around than natural processes such as rivers and glaciers. Wilkinson and McElroy 2007 quantifies sediment moved by humans versus natural processes. Zalasiewicz, et al. 2008 discusses stratigraphic evidence for starting the Anthropocene at the beginning of the Industrial Revolution. In addition to compiling evidence that humans move a great deal of sediment and leave distinctive indicators in sedimentary deposits, environmental geologists investigate human alteration of the dynamics of other materials, such as water and nutrients including nitrogen. Rockström, et al. 2009 proposes that humanity has exceeded critical levels on three planetary boundaries of sustainability related to climate change, rate of biodiversity loss, and the global nitrogen cycle. Steffen, et al. 2007 uses evidence of increasing concentrations of atmospheric carbon dioxide as indicators that humans are pushing Earth toward a tipping point of sustainability. Steffen, et al. 2015 updates the conceptualization of planetary boundaries and notes that exceeding the boundaries of either climate change and biosphere integrity has the potential to drive Earth systems into a new state.

  • Crutzen, P. J. 2002. Geology of mankind. Nature 415:23.

    DOI: 10.1038/415023aSave Citation »Export Citation »E-mail Citation »

    Influential paper proposing that because of anthropogenic emissions of carbon dioxide and associated changes in global climate, an Anthropocene epoch should be distinguished from the Holocene epoch that constitutes the most recent ten thousand years; increasing levels of carbon dioxide and methane levels in air trapped in polar ice cores coincide with invention of the steam engine in 1784.

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  • Hooke, R. LeB. 2000. On the history of humans as geomorphic agents. Geology 28:843–846.

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    One of the first studies to propose that humans now constitute the dominant influence on Earth’s landscape by moving more sediment than natural processes of erosion.

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  • Rockström, J., W. Steffen, K. Noone, et al. 2009. Planetary boundaries: Exploring the safe operating space for humanity. Ecology and Society 14:32.

    DOI: 10.5751/ES-03180-140232Save Citation »Export Citation »E-mail Citation »

    Influential paper examining global sustainability in the context of nine planetary boundaries; seven of these are quantified—climate change, ocean acidification, stratospheric ozone, biogeochemical nitrogen cycle and phosphorus cycle, global freshwater use, land system change, and rate of biodiversity loss; chemical pollution and atmospheric aerosol loading are unquantified boundaries.

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  • Steffen, W., P. J. Crutzen, and J. R. McNeill. 2007. The Anthropocene: Are humans now overwhelming the great forces of nature? AMBIO: A Journal of the Human Environment 36:614–621.

    DOI: 10.1579/0044-7447(2007)36[614:TAAHNO]2.0.CO;2Save Citation »Export Citation »E-mail Citation »

    Examines trends since 1800 CE in atmospheric carbon dioxide concentrations, which increased from 270 parts per million, or ppm prior to industrialization, to 310 ppm by 1950 and 380 ppm by 2007; speculates that the rapid rise during the late 20th century is pushing planetary systems toward a tipping point.

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  • Steffen, W., K. Richardson, J. Rockström, et al. 2015. Planetary boundaries: Guiding human development on a changing planet. Science 347:12.

    DOI: 10.1126/science.1259855Save Citation »Export Citation »E-mail Citation »

    Revises and updates the planetary boundaries framework in Rockström, et al. 2009 to better reflect interactions between the nine systems characterized via boundaries and to better reflect regional-scale heterogeneity in processes underpinning the boundaries.

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  • Wilkinson, B. H., and B. J. McElroy. 2007. The impact of humans on continental erosion and sedimentation. Geological Society of America Bulletin 119:140–156.

    DOI: 10.1130/B25899.1Save Citation »Export Citation »E-mail Citation »

    Rates of geomorphic change resulting from human activities now exceed those resulting from geologic processes; quantifies rates of glacial and river erosion through geologic time; the great majority of geologically derived sediment comes from a small proportion of Earth’s surface in the highest mountains, whereas humans primarily move sediment at lower elevations.

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  • Zalasiewicz, J., M. Williams, A. Smith, et al. 2008. Are we now living in the Anthropocene? GSA Today 18:4–8.

    DOI: 10.1130/GSAT01802A.1Save Citation »Export Citation »E-mail Citation »

    Reviews the stratigraphic evidence for designating the Anthropocene as a formal division of geologic time known as an epoch; stratigraphic evidence includes distinctive and novel biotic, sedimentary, and geochemical markers; advocates designating the Anthropocene as starting with the Industrial Revolution.

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