Evolutionary catastrophes : the science of mass extinction

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 caused mass extinction, and changed the path of evolution forever. Two main theories have emerged to account for these dramatic events: asteroid impact, and massive volcanic eruptions, both leading to nuclear-like winter. In recent years, the impact hypothesis has gained precedence, but Vincent Courtillot suggests that cataclysmic volcanic activity can be linked not only to the K-T mass extinction, but to most of the main mass extinction events in the history of the earth. Courtillot's book, first published in 1999, debunks some of the myths surrounding one of the most controversial arguments in science. This story will fascinate everyone interested in the history of life and death on our planet.

Reseñas (4)

Reseña de Publisher's Weekly

Originally published in France in 1995, this slim volume by a professor of geology at the University of Paris attempts to explain the causes of mass extinctions that have occurred over the past 300 million years. Courtillot does a superb job of presenting evidence for and against the two most likely factors: collisions of large asteroids with the earth and extensive volcanic activity. Although the popular belief is that asteroids are responsible, Courtillot argues persuasively that all available data are more consistent with the volcanic theory. Indeed, seven of the world's mass extinctions occurred when volcanic activity was at its peak, while only one, the extinction that took place 65 million years ago and wiped out the dinosaurs, among many other species, appears to have coincided with the impact of a major asteroid. Courtillot also discusses the personalities of some of the leading figures on both sides of the debate, as well as the nature of science. The book is fairly technical, however, so its appeal to a general readership may be limited. Illustrations. (July) (c) Copyright PWxyz, LLC. All rights reserved

Reseña de Booklist

The popular solution to the great dino murder mystery holds that an asteroid is the smoking gun. A competing culprit is smoking volcanoes. These briefs for the prosecution of each villain are both readable gateways to one of the more accessible controversies in contemporary science. A beleaguered voice in geology now that Walter Alvarez's impact theory (T. Rex and the Crater of Doom, 1997) has become the new orthodoxy, Courtillot's theory that volcanic eruptions tipped the environment against the dinosaurs is concisely ventilated here. The idea grew when his paleomagnetic dating team showed that the Deccan Traps in India erupted about the same time as T. rex expired, about 65 million years ago. Such traps (provinces of lava that flooded and solidified) correlate to hot spots, and when Courtillot rewinds the plate tectonics tape, he notices traps the world over approximate the time of other mass extinctions. For a triggering mechanism, he suggests the reversal of the earth's magnetic field, a provocative idea for the young geologists Courtillot hopes his book will inspire. A piece of precise, supple, open-minded analysis. Frankel, by contrast, writes a case-closed but still highly interesting version of how various evidence fingered the buried Chicxulub crater in Mexico as the relic of the dinosaurs' doom. The now-famous K-T boundary layer of clay in Italy and elsewhere had a concentration of iridium from which could be deduced the size of an asteroid and its resultant crater. Where was it? Shocked quartz narrowed the search to the Gulf of Mexico, and the bull's-eye was duly discovered. Frankel nods dismissively toward Courtillot's volcanism position, then surveys catastrophism's mark in other earthly craters, and uncomfortably close in the recent comet collision with Jupiter. A fluid, enthusiastic summary of the impact school's views. --Gilbert Taylor

Revisar OPCIONES

There have been few scientific debates in the 20th century as vigorous, acrimonious, and fruitful as those surrounding the mass extinctions at the end of the Cretaceous Period. Just when we thought that the asteroid impact hypothesis had thoroughly vanquished all foes, Courtillot (Institut de Physique du Globe de Paris) produces this short book to reintroduce an old player into the mass extinction game: massive volcanic eruptions. The centerpiece of the argument is a thorough analysis of the Deccan Traps, enormous outpourings of lava apparently spanning the Cretaceous-Tertiary boundary in India. These eruptions must have had a tremendous effect on the atmosphere and climate, Courtillot contends, and their correlation with the Cretaceous extinctions is more than coincidence. Although he has long been a partisan of the volcanic hypothesis, he gives a fair and balanced description of the evidence for an end-Cretaceous impact producing the Chicxulub crater, shocked quartz, an iridium anomaly, and other effects. His conclusion is that the eruptions had already placed life under considerable stress when the impact dealt a "further blow." Courtillot makes an excellent case for other mass extinctions being almost certainly related to cataclysmic volcanism. A well-written and well-reasoned book, essential for any library. General readers; undergraduates through professionals. M. A. Wilson; College of Wooster

Library Journal Review

"Science is not a democracy, and there is no room for political compromise," writes Frankel in reference to the raging debate over what caused the extinction of the dinosaurs. In one camp are the catastrophists, led by the discoveries of Walter and Louis Alvarez, who believe that a meteor impact was the cause; in the opposite corner, led by Courtillot (geophysics, Univ. of Paris), are the gradualists, who believe that dinosaur extinction was caused by long periods of intense volcanism. Walter Alvarez has already published a popular firsthand account of his own research (T. Rex and the Crater of Doom, LJ 6/15/97), and now Courtillot's popularized defense of the volcano extinction theory, first published in French in 1995, has been translated into English. Both of these books are fairly well written and appropriate for high school readers; the combination of the two will give junior scientists a good opportunity to consider and evaluate the evidence and arguments on both sides of the debate. On the side of the catastrophists (and most U.S. scientists are), Frankel, who is a planetary geologist and therefore more interested in meteors than dinosaurs, offers an excellent history of the research, as well as speculation on how to stop another large meteorite from striking Earth and causing the extinction of human beings. For all public libraries.ÄAmy Brunvand, Univ. of Utah Lib., Salt Lake City (c) Copyright 2010. Library Journals LLC, a wholly owned subsidiary of Media Source, Inc. No redistribution permitted.

Tabla de contenido

ForewordClaude AllFge

Preface

Preface to the English translation

1 Mass extinctions

2 An asteroid impact

3 From the roof of the world to the Deccan traps

4 The volcanic scenario

5 Plumes and hotspots

6 A remarkable correlation

7 Nemesis or Shiva?

8 Chicxulub

9 Controversy and coincidence

10 Improbable catastrophes and the flukes of evolution

Index

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