Buzz
In popular culture, dinosaurs are often depicted roaming hot and humid rainforests or swamps. However, colder climate settings for these creatures are much rarer, although evidence from research supports their historical accuracy. A recent study shows signs of freezing temperatures in higher latitudes around 201 million years ago, challenging the previously accepted belief that all Late Triassic dinosaurs thrived in warm climates. These findings may also explain how the feathered ancestors of T. rex managed to survive the mass extinction event that wiped out nearly half of all quadrupeds.
The study, published in the journal Science Advances, involved an international team of scientists who examined sediment samples from lakes in northern China that formed during the Triassic period. They discovered ancient minerals that likely made their way into deep waters through ice, suggesting that the lakes froze when they were still relatively young. The same sediment layers also contained dinosaur footprints, indicating that if temperatures dropped below freezing in northern China, cold conditions may have been widespread across the Arctic.
Many experts refer to the Earth during this time as a "hothouse" planet, and for good reason. Around 201 million years ago, as Pangea began to break apart, volcanic eruptions released a catastrophic amount of lava and debris. This caused carbon dioxide levels in the atmosphere to soar, reaching up to 4000 parts per million (compared to around 420 parts per million today). This resulted in a greenhouse effect that led to global warming. By the end of the Triassic period, 40 percent of all four-legged land animals had been wiped out.
The exact cause of the End Triassic Extinction and why it affected certain species while sparing others has remained unclear. A new study suggests that volcanic winters may have contributed to this event.
"We know the extinction was linked to, and likely triggered by, a continent-wide volcanic eruption," said Morgan Schaller, study co-author and associate professor of earth and environmental sciences at Rensselaer Polytechnic Institute, in an email to Mytour. "[...] The previous belief was that the extinction's cause was sudden (over a thousand years) global warming due to increased CO2, a potent greenhouse gas."
"While that certainly occurred, the more probable 'kill mechanism' for the extinction was a very brief (possibly decadal) but extreme cooling that immediately followed the volcanic eruptions."
Volcanic eruptions sent sulfate aerosols into the upper atmosphere, which may have reflected solar radiation away from Earth, resulting in colder temperatures at higher latitudes—much like the eruption of Mount Tambora in 1815, which caused Europe's "year without a summer." The study suggests that temperatures could have dropped by as much as 18 degrees following the Late Triassic eruptions.
Although these volcanic winters only lasted a few decades—brief in terms of geological time—their impact was likely significant. Many large land animals lacking natural insulation, such as large prehistoric crocodiles, perished. Meanwhile, smaller, insulated avian dinosaurs survived the End Triassic Extinction and later thrived in the succeeding era.
"The avian dinosaurs were most likely covered in feathers—providing them with insulation and making them well-suited for cold environments, which helped them survive the chilly volcanic winters," Schaller explains. "Until their non-insulated rivals (large, cold-blooded reptiles) were wiped out in the extinction event, these feathered dinosaurs couldn’t venture into warmer regions. Dinosaurs and their close relatives were actually cold-adapted species."
Feathers gave avian dinosaurs the edge they needed to survive on a tumultuous planet, enabling them to evolve into colossal predators, such as the Tyrannosaurus rex, which flourished up until the K–T extinction event.
This new research offers a fresh perspective on the mass extinction event at the end of the Triassic. Although it marked a time of widespread devastation, it also served as an opportunity for the most adaptable creatures on Earth to thrive and evolve in the face of catastrophic change.
