Evolutionary Catastrophes: The Science of Mass Extinction

By Vincent Courtillot

Book Overview

Why did the dinosaurs and two-thirds of all living species vanish from the face of the Earth sixty-five million years ago? Throughout the history of life a small number of catastrophic events have... This description may be from another edition of this product.

• Format: Hardcover
• Language: English
• ISBN: 0521583926
• ISBN13: 9780521583923
• Release Date: September 1999
• Publisher: Cambridge University Press
• Length: 188 Pages
• Weight: 1.06 lbs.
• Dimensions: 9.5" x 0.8" x 6.3"

Customer Reviews

The Impact of Catastrophes on Evolution

Vincent Courtillot graduated from the Paris School of Mines, Stanford University, and the University of Paris where he is a Professor of Geophysics. Courtillot studied the earth's magnetic fields, plate tectonics, magnetic reversals, and flood basalts. He published 150 papers in professional journals, and held many official jobs (p.i). The dinosaurs and most living species became extinct about 65 million years ago. Catastrophic events have cause mass extinction and affected evolution. There are two theories for this: asteroid impact, or massive volcanic eruptions, to cause extremely cold weather from a lack of sunlight. Courtillot suggests volcanic eruption caused most mass extinctions. The `Preface' notes that most species are extinct, and there were times when this was rapid along with the appearance of new species. The fossil records gave the answer. Geochemists and geophysicists sampled and analyzed the surviving records of metals and minerals. "Deciphering past catastrophes may perhaps be the only way of predicting the future effects of human activity on this planet's climate" (p.ix). Chapter 1 discusses mass extinction. There are a few "living fossils", but most species have a limited span of existence ranging from a few hundred thousand years to several million years (p.9). The Milankovic cycle cause variations in climate. Generally the larger or more specialized animals vanished, while the smaller or more generalized animals survived (p.16). Chapter 2 discusses an asteroid impact that led to a "nuclear winter" and the extinction of many species, such as dinosaurs (p.25). Magnetic anomalies in oceanic crusts suggest reversals in earth's magnetism over millions of years (p.54). The formation of the traps was about the same time when dinosaurs disappeared, hence the volcanist theory (p.56). Chapter 4 explains the effects of volcanic eruptions, such as in 1783 Iceland. The destruction of vegetation and cattle led to the greatest famine; a quarter of the population died (p.61). The sulfur content determines the climactic impact (p.62). Volcanism may explain the levels of arsenic, antimony, and selenium (p.67). Volcanic gases can explain the extinction of species 65 million years ago (p.72). The greatest mass extinction occurred at the end of the Paleozoic Era (p.88). Chapter 8 tells about the Chicxulub crater that was created by a giant asteroid and discovered by oil exploration. Courtillot explains why this wouldn't cause magnetic reversal (p.130). Attempts at scientific research often tell about the researchers as much as about the object of inquiry (Chapter 9). The example is the explanation for the disappearance of the dinosaurs: asteroid or volcanoes. The story of an asteroid impact seems more believable than centuries of volcanic eruptions (p.139). Eruptions coincide with seven mass extinctions (p.141). Chapter 10 says the gases of volcanism were sulfur dioxide, carbon dioxide, and hydrogen chloride. Human activity is now producing th

Controversial re-examination of geology's hottest topic

____________________________________________ We all know that a BIG meteor hit the Gulf of Mexico at the end of the Cretaceous and wiped out the dinosaurs, right? So, big meteor-strikes probably caused the other mass-extinctions too? Well -- the Chicxulub impact at the KT boundary, 65 my ago, is indeed well-documented. What's less well-known is that the Deccan Traps, an enormous outpouring of flood-basalts in what is now western India -- over 2 million cubic km(!) of lava, along with billions of tons of SO2, CO2, HCl, and other toxics -- were also in full eruption then. In fact, the famous KT iridium-signature has recently been identified in Deccan interflow sediments [note 1]. From recent radiometric dating, it looks like all of the Deccan eruptions occurred within a brief, 0.7 my time-span. The biggest and most violent eruptions apparently occurred within a few thousand years of the KT boundary; individual flows of several thousand cubic kilometers of basalt were not uncommon. Compare this to the largest historic 'flood'-basalt eruption: Laki in Iceland produced 12 cu. km of lava in 1783-84. The SO2 and other gases that Laki released, destroyed most of the island's crops and forage. Then 50-80% of the island's livestock, and about 1/4 of the Icelandic people, starved to death. Laki lowered global temperatures by about 1 deg. C (from fine-particle ash & sulfur aerosols). Extrapolating to a 5,000 cu. km flood-basalt eruption, the average global temperature might decrease by around 7 deg. C (13 deg. F). The volcanic HCl emissions could destroy most of the ozone layer [note 2], dramatically increasing UV at the surface, and injuring or killing many organisms. The familiar volcanogenic "toxics" -- F, As, Sb, Hg, Se etc. -- would poison nearby life. And the volcanic SO2 & HCl would cause severe acid-rain damage as they were washed out of the atmosphere. Then, repeat this disaster with the next big eruption, over & over again, a dozen or more times in the next 10,000 years or so. The total 'kill factor' would very likely be greater than that from the Chicxulub impact, albeit spread out over tens or hundreds of thousands of years. And a more gradual die-off is (usually) a better fit to the known fossil record. So it turns out that the volcanists and the meteor-strike proponents were *both* right, at least for the KT mass-extinction. The combination of the Chicxulub strike with the Deccan mega-eruption turned an 'ordinary' mass-extinction into the second-worst ever. And thoroughly muddied the scientific waters while this was being worked out. Once again, reality trumps fiction -- Nemesis atop Shiva! But, for the 10 or so "big" mass-extinctions known [note 3], *seven* are of the same age as major flood-basalt eruptions, vs. one or two with major same-age impacts. And those two meteor-strikes coincide with massive flood-basalt eruptions -- *no* major mass-extinctions appear to be solely impact-caused.

important information about geology and exciting

This kind of analysis and extrapolation adds a great deal of information for the layman who is willing to follow the discus- sion about geology and has background such as the Mcphee books, seismic theories of interior earth movements and plate tectonics. Because it is written by a French Scientist I feel it may not be given the attention it might if written by an American. It is slow going in the beginning because he explains the Alvarez discoveries and theories in more detail than I had previously had. When he gets to the discussion of the great volcanic events that created the huge lava plateaus such as the one in the Grand Coullee in Washington State, it gets very exciting because he gives a great deal of information that is new to me. This infor- mation brings a whole new dimension to plate techtonics, hot spots and possible extinctions. A great adventure in time.

Evolutionary Catastrophies.

Probably no single mass extinction of the five known to have occurred has captured popular notice so thoroughly as has the KT event. Ideas about what might have caused this disaster, which may have brought about the end of the dinosaurs, abound and range from change in the oxygen content of the atmosphere to astroid impacts. Mr. Courtillot, a French investigator of the Deccan Traps in India and China, has been the leading proponent of the volcanic-climatic disaster motif. In this book he defends his hypothesis, primarily against its leading opponent the Alvarez' astroidal impact theory, and believes that the evidence from the field more completely supports his theory of the cause of extinctions, not only at the KT boundary but through most of life's history. The volume is somewhat less readable than the Alvarez book (see T. Rex and the Crater of Doom or the review of it under my name), because it contains more technical information. The author defines many of his terms for the lay reader, but the discussion is definitely more understandable for the reader with some knowledge of geology in his/her background.