Evolutionary Catastrophes: The Science of Mass Extinction

by Vincent Courtillot, Joe McClinton (Translator)

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 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.

Genres: Science, History, Evolution, Nonfiction

188 pages, Paperback

First published August 26, 1999

Reviews

[Peter Tillman · Rating 4 out of 5]

We all know that a BIG meteor hit the Gulf of Mexico at the end of the Cretaceous period 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 million years (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. 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 km of basalt were common.

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 erupted, destroyed most of the island's crops and forage. Then 50-80% of the island's livestock, and about one quarter of the Icelandic people, starved to death. Laki lowered global temperatures by about 1 deg. C (from fine-particle ash and 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,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 and 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 and 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 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,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-extinction appears to be solely impact-caused. So it's fair to say that flood-basalts are more deadly to Earthly life than meteor-strikes. And a hazard not amenable to any engineering solution that I know of -- except being ready to move off the planet, when the next new hot-spot head nears breakout. Which will come, sure as death.4 An unpleasant reminder of our fragility and vulnerability.

Mea culpa: I'd pretty much taken the "KT impact killed off the dinos" theory as proven -- I didn't even bother to read the last volcanist counter-argument I saw. As Courtillot notes, I'm hardly the only one to do so. Hey, those guys are the old fuddy-duddies, right? The stamp-collectors, Luis Alvarez called them. Hence this review, a 'heads-up' to others, and an expiation for me.

Evolutionary Catastrophes is clearly written and is (mostly) accessible to the general reader. This is the latest chapter in the gradualist vs. catastrophist dialogue that is as old as geologic science. Writing with great good humour, skepticism, and a love for a scientific tale well-told, Courtillot goes a long way towards redressing the balance in the hottest earth-science argument at the turn of the 21st century. Highly recommended.

My 2000 review, with footnotes:
https://www.sfsite.com/05a/ec80.htm

[Tim Pendry · Rating 4 out of 5]

Although (my edition) is over two decades old (1999), which is quite a long time at the cutting edge of science, Courtillot's review of the science of mass extinction is still interesting on two grounds - it gives a fresh perspective from a French scientist and it restored volcanism as alternative to asteroids.

Neither of these aspects of the case is unimportant. Although Courtillot is unfailingly courteous about rival theories to his and open-minded as all good scientists should be, he is not shy of reminding us of the sociology of science and especially how American science can be conducted - often combatively.

This is not to say that Courtillot is right but only that he is civilised. The extinction of the dinosaurs by an asteroid has now become the default position of popular science. Yet we have also to account for many other evolutionary extinctions which bear on the case.

Courtillot is an advocate of volcanism being a major contributor to extinctions especially in relation to mega-events which create massive lava flows over extensive parts of continents over a much longer period of still concentrated time than asteroid impacts and which may correlate with extinctions.

He is not arguing that the Chickxulub asteroid was not a major contributor to the late-Cretaceous extinction but only that the contribution of the volcanism that formed the Deccan Traps has often been overlooked and asteroids are not easily found in previous extinctions where volcanism often is.

Part of his point is about how science is conducted. Even if he is proven wrong eventually, he is right on one score. The asteroid thesis has been driven into the popular imagination both by aggressive American individualism and group-think as well as by the way careers are made and media produced.

The implication (though he does not say this) is that science may be better served by a slightly slower pace, less brow-beating, more synergy between the many disciplines involved, more respect for some of them and more co-operation - more European, in fact.

I am in no position to adjudicate here but Courtillot (although he writes clearly) lays out a great deal of difficult technical research data (including that supportive of asteroid theorising). The book would prove a decent grounding for anyone wanting to investigate the matter further - and disagree.

The author also introduces us to thinking from a wide range of specialists and to research from a range of nationalities while opening the door wider to French institutional contributions. There is some corrective here to a purely Anglo-Saxon approach where science can be herd-like.

As of today, the issue of causes remains open (indeed a lot of the science of extinctions remains open even as to what such an event is). Flood basalt events (as Courtillot proposes), asteroid events and sea level fluctuations all remain plausible. Wikipedia has nine other 'possible causes'.

Unfortunately the Asteroid/Deccan Traps controversy got ridiculously vicious and personal as if it mattered too much to the individuals concerned. Courtillot's courtesy and scientific integrity seems to put at least some American science to shame in this respect.

The general reader will find some of the technical material a little hard going in places although it is not a subject that is well served by simplification or over-popularisation. My takeaway was to keep an open mind, accept the issue as complex and be wary of being bullied into submission by anyone.

[Spencer Stanhope · Rating 4 out of 5]

Now Vincent Courtillot has made an amazing non-fiction book about the theory of evolution, and the events of mass extinction. He will take you on a journey of what happened during the mass extinctions of many animals, and how animals were able to live and make it here today.
Mr. Courtillot will take you on a journey back through what happened during the mass extinctions, and the reason why dinosaurs just vanished off the face of the earth. He will talk to you about the two events that have led to the extinctions which are, the asteroid that hit the earth and the giant volcanoes that erupted in the years. He will also talk about the theory of evolution that helped keep living creatures alive during mass extinctions, and how animals grow to help them live through deadly events.
I would recommend this book to people who liked to learn about what happened to the dinosaurs, and other mass extinction events. I feel like Ari would like this book. I liked this book because it had a lot of information that I didn’t know before I read this, so I liked all the things I gained from reading this book. But I also didn’t like the book because there was so much information in the book, that it was kinda hard to keep track of the things I learned so far in the book. Overall this book was very interesting to me, and I liked that I could learn so much about something but, not have to take that long of a time to get through.

[Jani-Petri · Rating 3 out of 5]

Nice book. A bit centered on French, but interesting nevertheless.