Mass Extinction

by

Paul B. Wignall

• LAST REVIEWED: 28 March 2018
• LAST MODIFIED: 28 March 2018
• DOI: 10.1093/obo/9780199941728-0102

Introduction

Mass extinctions are the worst crises that human life has ever faced. They are defined as geologically brief intervals, ranging from decades to tens of thousands of years in duration, that saw enormous increases in extinction rates above background values. They are also unique in that they affected animals and plants in all habitats and latitudes and are also the only times when the ocean’s plankton suffered major extinctions. Inevitably such gigantic events were recognized during the earliest investigations of the fossil record in the 19th century and the major changeovers in the dominant fossil groups provided good markers to divide up geological time. Not surprisingly most mass extinctions were chosen to mark major interval boundaries such as the end of the Ordovician, end of the Permian, and the end of the Cretaceous. However, the idea of abrupt, catastrophic mass extinction events did not gain much credence until 1980 with the discovery of evidence that the death of the dinosaurs, at the end of the Cretaceous, coincided with a huge meteorite impact. Since that time the study of mass extinctions has become a major research area within the field of earth sciences. There are many ongoing intense debates, not least of which is the relative importance of meteorite impact and volcanism as the driving cause of mass extinctions. Despite the initial discovery of the end-Cretaceous impact, now known to have been at Chicxulub in Mexico, no other mass extinction has been convincingly linked to a meteorite impact event. Instead, the most frequent link is with giant phases of volcanism that produced flood basalt provinces (also known as large igneous provinces or LIPs). Interestingly, even the end-Cretaceous mass extinction coincides with a LIP eruption—the Deccan Traps of India, for example—thus providing an alternative cause for the dinosaur extinction that has led to intense debates over the past thirty years. Despite the controversy, mass extinctions were caused by massive global climatic and environmental changes. Frequently the changes are bound up with rapid phases of global warming and its consequential effects. Thus, there is a link to modern climatic concerns, and as ancient experiments of what happens when the climate warms up fast, mass extinctions provide important past scenarios that can help us understand the near future.

General Overviews

Most of the concepts and ideas concerning mass extinctions began to develop in the 1980s following the development of the meteorite impact story for dinosaur extinctions. By the 1990s the first books were starting to appear that synthesized this rapidly growing research field. However, Hallam and Wignall 1997 was and remains the only volume to summarize the entire field, including the many lesser extinction events. It was state of the art in its day and is still valuable, although the more recent advances made in understanding some mass extinctions (notably at the end of the Triassic) is considerable. A more concise synthesis, with an emphasis on the role of volcanism during mass extinction can be found in Hallam 2004, while MacLeod 2013 is an excellent general overview aimed at the general public. More recently Wignall 2015 has focused on the cluster of mass extinctions that occurred from the Middle Permian to the Early Jurassic and provided a model that explains why volcanism was such an effective and frequent cause of mass extinction at this time. The alternative, that meteorites caused all extinctions, is provided by Raup’s polemical tome from 1991 (Extinction: Bad Genes or Bad Luck?). However, the popular viewpoint in the 1980s that meteorites played a role in many extinctions now receives little support in the geological community—with the obvious exception of the end-Cretaceous impact. The end-Cretaceous mass extinction is by far the most famous of the “big five” mass extinctions of the fossil record and has been the subject of several popular science books of which Alvarez 1997 is the most entertaining: it is written by one of the team who originally made an iridium discovery that pointed to meteorite impact. For a more balanced overview of the field, Powell 1998 does a good job. There is a need for a more updated synthesis, one that takes into account the major advances in documenting the timing of extinctions and eruption history of the Deccan Traps. The greatest mass extinction of the fossil record occurred at the Permo-Triassic (P-T) boundary, and this has been much better served in the 21st century by popular science books. Thus, Erwin 2006 provides a thorough review and Peter Ward has also published several popular science books that tend to focus on specific aspects of mass extinction stories with his 2009 volume on the role of anaerobic microbes being a typical example.

• Alvarez, W. 1997. T. rex and the crater of doom. Princeton, NJ: Princeton Univ. Press.

  An insider’s story on the discovery of the iridium anomaly at the K-T boundary and how this lead to the debates in the 1980s between pro-impactors and volcanologists.

• Erwin, D. H. 2006. Extinction: How life on earth nearly ended 250 million years ago. Princeton, NJ: Princeton Univ. Press.

  A major review of all aspects of the Permo-Triassic mass extinction as understood at the time. Avoids favoring any one extinction mechanism cause (not necessarily a good thing) by going for the “everything did it including the kitchen sink” approach.

• Hallam, A. 2004. Catastrophes and lesser calamities: The causes of mass extinctions. Oxford: Oxford Univ. Press.

  Probably the most accessible, short summary of mass extinctions and the role of volcanism that is available. Still pertinent today despite being over a decade old.

• Hallam, A., and P. B. Wignall. 1997. Mass extinctions and their aftermath. Oxford: Oxford Univ. Press.

  Aimed at the level of the university student, this book is somewhat dated now. But even in the late 1990s most of the main ideas and debates on the big five mass extinctions were well established and can be found here. It is also the only summary available of all the lesser extinction crises of the Phanerozoic and was the first book to consider the nature of recovery from mass extinctions.

• MacLeod, N. 2013. The great extinctions: What causes them and how they shape life. London: Natural History Museum.

  This book was produced to accompany a new extinction gallery at the Natural History Museum, London, and is intended as a guide for the general public. As a result, it is the most accessible summary of mass extinctions available and is particularly good at summarizing what went extinct and when.

• McGhee, G. R., Jr. 2013. When the invasion of land failed: The legacy of the Devonian extinctions. New York: Columbia Univ. Press.

  The only popular science book to focus on the Late Devonian mass extinction. It is especially interested in the fate of the earliest amphibians, which were just starting to crawl from the water at that time. However, other aspects of the Late Devonian crisis get little coverage.

• Powell, J. L. 1998. Night comes to the Cretaceous. New York: W. H. Freeman.

  Long in the tooth but a nice summary of the K-T mass extinction story for its day.

• Raup, D. M. 1991. Extinction: Bad genes or bad luck? New York: W. W. Norton.

  A short, well-written polemic arguing that all mass extinctions were caused by meteorite impact. The answer to the title question is therefore bad luck.

• Ward, P. 2009. The Medea hypothesis. Princeton, NJ: Princeton Univ. Press.

  Looks at the role of anaerobic microbes and posits that they played a significant part in causing oceanic mass extinctions such as that at the end of the Permian.

• Wignall, P. B. 2015. The worst of times: How life on earth survived eighty million years of extinctions. Princeton, NJ: Princeton Univ. Press.

  DOI: 10.1515/9781400874248

  An up-to-date review of the major and minor extinctions in the 80 million years, starting in the Permian and ending in the Jurassic. Argues that the combination of supercontinent geography and giant volcanism were in a uniquely lethal combination.