Sixth extinction? One is newly identified (Introduction)

by David Turell , Wednesday, September 16, 2020, 20:26 (1319 days ago) @ David Turell

This is newly identified as a mass extinction:

https://phys.org/news/2020-09-discovery-mass-extinction.html

"...an international team has identified a major extinction of life 233 million years ago that triggered the dinosaur takeover of the world. The crisis has been called the Carnian Pluvial Episode.

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"The cause was most likely massive volcanic eruptions in the Wrangellia Province of western Canada, where huge volumes of volcanic basalt was poured out and forms much of the western coast of North America.

"'The eruptions peaked in the Carnian," says Jacopo Dal Corso. "I was studying the geochemical signature of the eruptions a few years ago and identified some massive effects on the atmosphere worldwide. The eruptions were so huge, they pumped vast amounts of greenhouse gases like carbon dioxide, and there were spikes of global warming".The warming was associated with increased rainfall, and this had been detected back in the 1980s by geologists Mike Simms and Alastair Ruffell as a humid episode lasting about 1 million years in all. The climate change caused major biodiversity loss in the ocean and on land, but just after the extinction event new groups took over, forming more modern-like ecosystems. The shifts in climate encouraged growth of plant life, and the expansion of modern conifer forests.

"'The new floras probably provided slim pickings for the surviving herbivorous reptiles," said Professor Mike Benton. "I had noted a floral switch and ecological catastrophe among the herbivores back in 1983 when I completed my Ph.D. We now know that dinosaurs originated some 20 million years before this event, but they remained quite rare and unimportant until the Carnian Pluvial Episode hit. It was the sudden arid conditions after the humid episode that gave dinosaurs their chance."

"It wasn't just dinosaurs, but also many modern groups of plants and animals also appeared at this time, including some of the first turtles, crocodiles, lizards, and the first mammals.

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"'So far, palaeontologists had identified five "big" mass extinctions in the past 500 million yeas of the history of life," says Jacopo Dal Corso. "Each of these had a profound effect on the evolution of the Earth and of life. We have identified another great extinction event, and it evidently had a major role in helping to reset life on land and in the oceans, marking the origins of modern ecosystems.'"

Comment: It follows a previous pattern wiping out large groups and allowing new ones to appear. Each event advances the complexity of life. That can't be chance but purposeful.