Karst Caves

by

Mario Parise

• LAST REVIEWED: 26 July 2017
• LAST MODIFIED: 26 July 2017
• DOI: 10.1093/obo/9780199363445-0078

Introduction

Karst refers to the processes of chemical dissolution and mechanical erosion acting on soluble rocks (mainly carbonates and evaporites), and to the surface and subsurface landforms thus produced. In their book Karst Hydrogeology and Geomorphology, Derek Ford and Paul Williams state that about 20 percent of the emerged Earth’s surface is karst, with caves representing a typical and well-known expression (see Ford and Williams 2007, cited under Karst Hydrogeology: The Importance of Karst Aquifers). Together with caves, karst lands are characterized by underground drainages and by scarce presence of water running at the surface. Water, rather than flowing on the ground as watercourses and rivers, rapidly infiltrates underground through networks of fissures and conduits, which combine to the diffuse flow in recent carbonates, giving origin to the complex systems of karst caves. Karst environments and caves have been of interest to humans since the earliest civilizations—for water supply, as settlements or areas of protection, or to bury the dead. Some of the more ancient testimonies of art are within caves, such as those in several caverns of the Mediterranean area (including, to mention the most remarkable, Lascaux and Chauvet in France, Altamira in Spain, and Porto Badisco in Italy). Karst research, which is linked to caving exploration, had a great impulse in the second half of the 20th century. Caves have been recognized as a very precious and peculiar environment, where traces of the past, in terms of sediments (see Sasowsky and Mylroie 2004, cited under Cave Deposits) or evidence of paleoclimate (see Fairchild and Baker 2012, cited under Contribution to Paleoclimatic Studies), have been preserved, often in great detail, in contrast to what occurs at Earth’s surface, where most of it is being destroyed, canceled, or covered by later processes. As a consequence, the classical studies about speleogenesis (that is, the origin of caves) and on geomorphology of the underground settings have developed in integration with those by researches in other disciplines, covering, among others, cave sediments, biospeleology and microbiology, and dating of speleothems for paleoclimatic and paleoenvironmental studies. Further, the expansion of built-up environments and construction in karst lands resulted in the interaction among natural hazards in karst and society, as pointed out in Parise and Gunn 2007 (under Karst Hazards), and Gutiérrez, et al. 2014 (under Human Impacts and Land Management in Karst), bringing to general attention the issue of fragility of karst, due to its peculiar hydrologic and hydrogeological features. As a matter of fact, Goldscheider and Drew 2007 (under Karst Hydrogeology: The Importance of Karst Aquifers) documents that karst aquifers are of high quality and represent between 20 and 25 percent of the world’s drinking resources, but that they are also extremely vulnerable and potentially threatened by a variety of forms of pollution.

History of Karst Research: Developing the Main Concepts

The term karst derives from the Indo-European root “kar,” meaning rock. It refers to the typical karst landscape at the surface, characterized by exposure of bare rock, with very limited, if not absent, soil cover. Karst also designates a geographical area, namely the region covering northeastern Italy and southwestern Slovenia, also known as Classical Karst, where the first organized explorations and the first scientific studies about karstology and speleology began during the first half of the 19th century, as documented in Cvijic 1918. Since then, many different theories have been proposed, from different parts of the world, in order to explain the processes acting in cave formation, as well as the consequent evolution of both caves and the overlying landscape. This section briefly summarizes the main works of historical importance for the development of the first ideas about karst and caves, shared among cavers, karstologists, and karst scholars around the world. Papers such as Davis 1931, Bretz 1942, Davies 1951, Ewers 1966, and Thrailkill 1968, even though dating back many decades, are still today considered milestones in the karst literature; more recently, they were followed by other remarkable works, such as Ford and Ewers 1978 and Palmer 1991.

• Bretz, J. H. 1942. Vadose and phreatic features of limestone caverns. Journal of Geology 50:675–811.

  A pioneering work describing the main features of karst caves, formed in vadose and phreatic conditions. Many underground landforms are presented and interpreted, offering several ideas and development to later scholars for understanding the processes acting in both the shaping and the evolution of caves.

• Curl, R. L. 1974. Deducing flow velocity in cave conduits from scallops. National Speleological Society Bulletin 36:1–5.

  Theoretical and experimental findings about the dissolutional patterns called scallops are presented in this paper, together with considerations aimed at deducing the paleohydrologic conditions in caves. Scallops are produced by the turbulent flow of water along soluble rocks, and the statistical analysis of their shape and morphometric parameters may be used to obtain information on the hydrodynamic processes leading to their genesis, and to flow velocity.

• Cvijic, J. 1918. Hydrographie souterraine et évolution morphologique du Karst. Recueil des Travaux de l’Institute de Géographie Alpine 4:375–426.

  A fundamental piece of work for karst research, such that the author is often called “the father of karst geomorphology and hydrology.” Through a number of examples from the Classical Karst, Cvijic systematically treated the main karst landforms, while also proposing different morphologic types for limestone terrains: holokarst, merokarst, and transition karst. This work has been, and still is, a remarkable reference for all karst scientists, in Europe and elsewhere.

• Davies, W. E. 1951. Mechanics of cavern breakdown. National Speleological Society Bulletin 13:36–43.

  This work describes the main mechanisms of cavern breakdown, at the origin of the production of the related deposits, that characterize cave systems in their final stages of evolution. It is one of the first pieces of work entirely dedicated to these mechanisms.

• Davis, W. M. 1931. The origin of limestone caverns. Science 73.1891: 327–331.

  One of the first attempts to delineate the origin of karst caves. Following a full paper published the year before, Davis describes the processes acting in the formation of caverns (solutional work by percolating vadose water) and in their replenishment with dripstones and speleothems. It is worth noting the attention Davis gives to discriminating among different processes, aimed at a correct understanding of those involved in the initial stages of cave formation.

• Ewers, R. O. 1966. Bedding-plane anastomoses and their relation to cavern passages. National Speleological Society Bulletin 28:133–140.

  Bedding-plane anastomoses, a typical cave feature produced in phreatic conditions, are described in this paper, which presents an interpretation of their development and evolution in relation to the local stratigraphic setting of the carbonate rock mass, based upon field evidence and experiments.

• Ford, D. C., and R. O. Ewers. 1978. The development of limestone cave systems in the dimensions of length and depth. Canadian Journal of Earth Sciences 15:1783–1798.

  A four-state model is proposed to explain the formation of vadose and phreatic caves. In this model, ideal phreatic and water-table caverns are end members. For each given karst massif, the cave type that is going to develop is a function of the frequency of fissures penetrable by groundwater. Complete cave systems may include all different types (vadose, phreatic, and/or water-table components), developed contemporaneously.

• Mylroie, J. E., and J. L. Carew. 1990. The flank margin model for dissolution cave development in carbonate platforms. Earth Surface Processes and Landforms 15:413–424.

  In this frequently cited paper, starting from observations on caves in the Bahama Islands, a model is proposed to explain the occurrence of rapid significant dissolution as a result of mixing fresh and marine waters beneath small carbonate islands. The flank margin model proposes that beneath the margin of marine inundated aeolian ridges, a dissolutionally aggressive halocline mixing zone developed, creating the conditions necessary for the origin of large dissolution caves.

• Palmer, A. N. 1987. Cave levels and their interpretation. National Speleological Society Bulletin 49:50–66.

  A very important piece of work, where the concentration of passages at common levels within solution caves is used to interpret the cave evolution in relation to its regional geological setting. Among the many interesting outcomes, it is pointed out that some levels in caves formed by short-lived processes may not represent static base levels, and should therefore be treated with caution when trying to reconstruct the cave evolution.

• Palmer, A. N. 1991. Origin and morphology of limestone caves. Geological Society of America Bulletin 103:1–21.

  The paper focuses on the origin of the basic cave patterns and on rates of cave enlargement. The solutional origin of caves in carbonate rocks is explored, with conclusions supported by field surveys in about five hundred caves, supplemented by other available published data. It is demonstrated that geologic structure and stratigraphy influence cave orientation and development, but they do not alone determine the main character of cave systems.

• Thrailkill, J. 1968. Chemical and hydrologic factors in the excavation of limestone caves. Geological Society of America Bulletin 79.1: 19–46.

  An attempt to investigate hydrologic and chemical processes to explain the development of caves in the region just beneath the water table, with a particular focus on the differences between the Darcy flow of granular aquifers and the laminar or turbulent flow of limestone aquifers, and on the ways in which water in the limestone aquifer may become undersaturated with respect to calcite.