A massive volcanic eruption about 202 million years ago had a profound effect on Earth’s climate, triggering a mass extinction event that killed three-quarters of Earth’s species, including many large reptiles. Yet, somehow, the dinosaurs survived and continued to thrive.
Dinosaurs are generally considered to be heat-loving, well suited to the humid greenhouse environment of the Triassic. But unlike other reptiles of the time, their secret to survival may have been their resilience to cold.This Dinosaur Warm Feather Coat Researchers on July 1 at scientific progress.
“We’ve known for a long time that there may be volcanic winters” associated with massive eruptions, said Paul Olson, a paleontologist at Columbia University’s Lamont-Doherty Earth Observatory.In addition to carbon dioxide, volcanoes spew sulphur particles into the atmosphere, darkening skies for years and lowering global temperatures – just like the Philippines Mount Pinatubo does it after its strong 1991 break out(Serial Number: 8/8/18). “But how [such winters] Whether it fits the picture of the end-Triassic mass extinction is unclear. “
In the new study, Olson and his colleagues present the first physical evidence that such winters not only occurred at the end of the Triassic, but dinosaurs spent them there. At a site called the Junggar Basin, which was high above the Arctic Circle at the end of the Triassic, the team identified rock fragments that could only have been deposited next to dinosaur footprints by ancient ice.
“There is a stereotype that dinosaurs always lived in dense tropical jungles,” said Stephen Brusatte, a paleontologist at the University of Edinburgh who was not involved in the new study. “But this new study convincingly shows that at the dawn of the dinosaurs, high latitudes were frozen or even covered in ice for part of the year,” he said.
The Triassic ended with a bang that began about 202 million years ago, when the supercontinent Pangaea began to break up. As the crust split, a massive volcanic eruption erupted, opening up a basin that became the Atlantic Ocean. The hardened lava from these eruptions now spans 7 million square kilometers across Africa, Europe, and North and South America, forming a rock sequence collectively known as the Central Atlantic Magma Province (CAMP).
During the late Triassic and early Jurassic, carbon dioxide levels were very high, and much of it is now thought to have been emitted into the atmosphere by these volcanic eruptions. Therefore, the earth is considered to be in a humid greenhouse state. Supporting this hypothesis is the fact that there was no evidence of any polar ice caps at the time; instead, dense forests stretched all the way to the poles.
The Junggar Basin in what is now northwestern China is one such area, covered with forests of coniferous and deciduous trees, next to a huge ancient lake. Dinosaurs did live there: no bones have yet been found at the site, but the footprints of many creatures have been preserved in the shallow-water siltstone and sandstone formed at the bottom of the lake.
New data suggest – despite extremely high levels of carbon dioxide2 Water Levels – The region has also experienced severe, cold winters with the lake at least partially frozen. Evidence comes from the same rocks as the footprints. By analyzing the distribution of particle sizes in the rocks, the researchers determined that most of the particles were not part of the original lake mud, but were transported from elsewhere.
The most likely explanation, Olson said, is that the particles are “ice drift debris” — a well-known phenomenon in which rock fragments freeze along coastlines to the bottom of the ice and then hitch a ride on the ice. Eventually drifted into open water. As the ice floes melted, rock fragments sank, depositing in new areas.
Volcanic winters can last for decades or even centuries, depending on how long the volcano continues to erupt, Olson said.In this case, the huge lava sheet associated with the CAMP eruption points to at least tens of thousands Years of Eruption Pulse, maybe even a million years. He added that this could have kept winter long enough — long enough to drive many poorly insulated reptiles off the planet. The onset of these freezing conditions may even extend as far as the tropics, the team said.
Evidence of feathers has been found in fossils from carnivorous theropods to herbivorous ornithischian dinosaurs.There have been recent reports that flying reptiles are called pterosaurs have feathers It is also now shown that insulating villi have been around for longer than previously thought – possibly appearing in the common ancestor of dinosaurs and pterosaurs as early as 250 million years ago (SN: 4/29/22).
Thanks to these insulating feathers, the dinosaurs were able to survive the long winters during the end-Triassic mass extinction, Olson and his colleagues say. Dinosaurs likely spread rapidly during the Jurassic, occupying the vacant niches left by less hardy reptiles.
Randall Irmis, a paleontologist at the University of Utah in Salt Lake City, said the study “shows not only the complexity of unraveling the success of certain groups, but also the causes and effects of mass extinction events.” , who was not involved in the study. “There is a good consensus that [the CAMP eruptions are] The cause of the mass extinction — but there are a lot of subtleties we don’t realize. “
Dinosaurs living in the far north at the time were able to survive because of their feathery insulation, Yilmis said. But whether the volcanic winters caused by the dimming would extend southward enough to freeze the tropics too — giving dinosaurs a similar advantage there — is unclear. “Dimming is a global effect, but the impact is much more severe at the poles than at lower latitudes.”
Feathers may have been just one of the many reasons why dinosaurs diversified and spread rapidly across the globe in the early Jurassic period, Elmis said. “There are many reasons why they’ve been such a successful group.”