The End Triassic Mass Extinction

Lately I've been writing about the history of the Earth and life on it during these last 3.5 billion years. This post is about the end Triassic extinction, which occurred about 200 million years ago, but before I report on this latest study I'd like to make a few remarks about the "near" future, which we might define as the next 200 years. As any geologist or paleontologist knows, 200 years does not even show up on the geological time scale.

One good reason to write about the history of life on Earth is that by and large humans don't know anything about it. This is especially true of optimists, for an important thing that keeps their optimism afloat is their ignorance of the deep past. The ignorant optimist does not (and can not) assess risks. Everybody has an opinion about global warming, but very few people are informed by some knowledge of paleoclimate or previous mass extinctions. And here I am referring to "expert" opinions. I don't expect the hoi polloi to read articles which appear in Nature or Science.

Take your run-of-the-mill economist. (Please!) This person knows nothing about the history of life on the Earth. Zilch, nadda, zip. Economists are completely unqualified to evaluate the consequences of a 2-4° centrigrade rise in the average surface temperature of the Earth, a prospect which is nearly a dead certainty. And since this economist lives in a state of total ignorance about these matters, he can confidently tell you that the human-made economy will grow and grow in the future without interruption from Mother Nature.

In this context, let's look at the end Triassic extinction. I'll quote from Science Daily's Megavolcanoes Tied to Pre-Dinosaur Mass Extinction: Apparent Sudden Climate Shift Could Have Analog Today.

Scientists examining evidence across the world from New Jersey to North Africa say they have linked the abrupt disappearance of half of earth's species 200 million years ago to a precisely dated set of gigantic volcanic eruptions. The eruptions may have caused climate changes so sudden that many creatures were unable to adapt -- possibly on a pace similar to that of human-influenced climate warming today. The extinction opened the way for dinosaurs to evolve and dominate the planet for the next 135 million years, before they, too, were wiped out in a later planetary cataclysm...

In recent years, many scientists have suggested that the so-called End-Triassic Extinction and at least four other known past die-offs were caused at least in part by mega-volcanism and resulting climate change. However, they were unable to tie deposits left by eruptions to biological crashes closely in time. This study provides the tightest link yet, with a newly precise date for the ETE — 201,564,000 years ago, exactly the same time as a massive outpouring of lava...

The new study unites several pre-existing lines of evidence by aligning them with new techniques for dating rocks. Lead author Terrence Blackburn (then at Massachusetts Institute of Technology; now at the Carnegie Institution) used the decay of uranium isotopes to pull exact dates from basalt, a rock left by eruptions. The basalts analyzed in the study all came from the Central Atlantic Magmatic Province [CAMP], a series of huge eruptions known to have started around 200 million years ago, when nearly all land was massed into one huge continent. The eruptions spewed some 2.5 million cubic miles of lava in four sudden spurts over a 600,000-year span, and initiated a rift that evolved into the Atlantic Ocean; remnants of CAMP lavas are found now in North and South America, and North Africa [image left]. The scientists analyzed samples from what are now Nova Scotia, Morocco and the New York City suburbs. (Olsen hammered one from a road cut in the Hudson River Palisades, about 1,900 feet from the New Jersey side of the George Washington Bridge.)

Previous studies have suggested a link between the CAMP eruptions and the extinction, but other researchers' dating of the basalts had a margin of error of 1 to 3 million years. The new margin of error is only a few thousand years — in geology, an eye blink. Blackburn and his colleagues showed that the eruption in Morocco was the earliest, with ones in Nova Scotia and New Jersey coming about 3,000 and 13,000 years later, respectively.

Here is the connection to what is happening in contemporary times.

Many scientists assume that giant eruptions would have sent sulfurous particles into the air that darkened the skies, creating a multi-year winter that would have frozen out many creatures. A previous study by Kent and Rutgers University geochemist Morgan Schaller has also shown that each pulse of volcanism doubled the air's concentration of carbon dioxide — a major component of volcanic gases.

Following the cold pulses, the warming effects of this greenhouse gas would have lasted for millennia, wiping out creatures that could not take too much heat. (It was already quite hot to begin with at that time; even pre-eruption CO₂ levels were higher than those of today.) Fossils show that heat-sensitive plants especially suffered; there is also evidence that the increased CO₂ caused chemical reactions that made the oceans more acidic, causing populations of shell-building creatures to collapse...

The End Triassic was the fourth known global die-off [mass extinction]; the extinction of the dinosaurs was the fifth. Today, some scientists have proposed that we are on the cusp of a sixth, humanmade, extinction. Explosive human population growth, industrial activity and exploitation of natural resources are rapidly pushing many species off the map. Burning of fossil fuels in particular has had an effect, raising the air's CO₂ level more than 40 percent in just 200 years — a pace possibly as fast, or faster, than that of the End Triassic. Resulting temperatures increases now appear to be altering ecosystems; and CO₂ entering seawater is causing what could be the fastest ongoing acidification of the oceans for at least the last 300 million years, according to a 2012 study.

"In some ways, the End Triassic Extinction is analogous to today," said Blackburn. "It may have operated on a similar time scale. Much insight on the possible future impact of doubling atmospheric CO₂ on global temperatures, ocean acidity and life on earth may be gained by studying the geologic record."

In fact, the end Triassic mass extinction happened very slowly compared with what is happening now, at least on the human time scale. On the geological time scale, there is no difference.

And yet, tomorrow, and the day after that, and the day after that, some economist is going to tell us with great confidence how rosy the future looks. Jesus wept.

Comments

[J.Drew]

Come on Dave, Just think about the exciting growth opportunities in the marine plankton harvesting and processing industry as "conventional" (so old fashioned!) resources become scarce.