‘Volcanic winters’ may have allowed large dinosaurs to emerge

‘Volcanic winters’ may have allowed large dinosaurs to emerge

In popular media, dinosaurs are often shown sneaking through scorching rainforests or sweltering swamps. Depictions of creatures in colder environments are much rarer, but research indicates they have some basis in history. A new study shows evidence of freezing temperatures at higher latitudes around 201 million years ago, contradicting the long-held assumption that all Upper Triassic dinosaurs lived in warm environments. The results could also explain how T. rex’Its feathered ancestors survived the extinction that wiped out nearly half of all quadrupeds.

For their study, published in the journal Scientists progress, an international team of scientists analyzed the sediments of lakes in northern China that formed during the Triassic period. They found ancient minerals that they suspected had been transferred to deep waters by the ice, indicating that the lakes had frozen over when they were still quite young. The rock strata containing the minerals also bore dinosaur footprints. If temperatures in northern China dipped below freezing at that time, cold weather was likely felt throughout the Arctic region.

Many experts describe Earth during this time as a “hothouse” planet, and for good reason. When Pangea began to crumble about 201 million years ago, the volcanoes spewed out an apocalyptic amount of lava and debris. Carbon dioxide levels in the atmosphere doubled to 4000 parts per million (it’s about 420 parts per million today). This triggered a greenhouse effect that sent the planet into global warming. By the end of the Triassic period, 40% of all four-legged land animals were extinct.

The exact cause of the Late Triassic extinction, and why it impacted some species and not others, is unclear. The new study shows that volcanic winters may have played a role.

“We know that the extinction was associated with, and most likely triggered by, a continental-scale volcanic eruption,” said Morgan Schaller, study co-author and associate professor of earth and geosciences. environment at Rensselaer Polytechnic Institute, in an email to Mental Floss. “[…] the previous thought was that the mechanism of destruction during the extinction was due to sudden global warming (on the scale of a thousand years) due to the increase in CO2 (a fairly effective greenhouse gas).”

“While it certainly happened, the most likely ‘killing mechanism’ of the extinction was a very short-lived extreme (decadal?) cooling that immediately followed the eruptions.”

Sulfate aerosols thrown into the upper atmosphere by volcanoes may have reflected solar radiation away from Earth, resulting in cold weather at higher latitudes, similar to the way the volcanic eruption of Mount Tambora in 1815 led to Europe’s “year without a summer”. According to the study, temperatures may have dropped by 18 degrees after the Upper Triassic eruptions.

Although these volcanic winters only lasted decades before global warming took over – a blink of an eye in geologic time – the effects were likely to be profound. Many large land animals without built-in insulation, such as large-bodied prehistoric crocodiles, perished during this time. Smaller isolated avian dinosaurs, meanwhile, were able to survive the Late Triassic extinction event and dominate the next era.

“Avian dinosaurs were most likely feathered, meaning they had effective insulation and were cold-adapted, allowing them to survive the cold temperatures produced by volcanic winters,” Schaller says. “Until their non-isolated competitors (large non-isolated reptiles) were wiped out by extinction, the feathered dinosaur forms could not move through the tropical realms. Dinosaurs and their close relatives are actually forms animals adapted to the cold.

Feathers allowed avian dinosaurs to thrive on an unstable planet and evolve into massive predators, like the tyrannosaurus rexwhich thrived until the extinction of K–T.

The new research paints the mass extinction event at the end of the Triassic in a new light. Although it was a time of death and destruction for much of the planet, it was also an opportunity for adaptation and survival for Earth’s most resilient creatures.

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