(CN) — Four episodes of intense volcanic activity over a two-million-year period released an extraordinary amount of carbon dioxide into the atmosphere, increasing the global temperature and humidity and setting the stage for the rise of dinosaurs.
This period known as The Late Triassic Carnian Pluvial Episode (CPE), occurred over 230 million years ago.
Researchers from the University of Birmingham and others analyzed sediment and fossil plant records derived from a lake in northern China’s Jiyuan Basin, matching episodes of volcanic activity with substantial environmental changes, as far back as 234 million years ago. They published their findings Monday in the journal Proceedings of the National Academy of Sciences.
“Our study used radiometric dating of volcanic ash horizons to allow us to determine how old the rocks we studied were. This allowed us to compare the rocks we had from our continental settings with similar aged geological succession from other parts of the world, and importantly, to marine rocks,” study author Jason Hilton said in an email.
Other methods employed by the scientists involved in the study included uranium-lead zircon dating, high-resolution chemostratigraphy and analysis of palynological and sedimentological data.
“When we looked at the initial results, we thought we had something special, but it was only when we got the ages for the ash horizons that it all started to fall into place and we knew we had the Carnian Pluvial Event,” Hilton wrote in the email. “The Carnian Pluvial Episode was a remarkable time in Earth history from which massive scale igneous activity in North America affected climates and environments globally.”
Dr. Emma Dunne, a paleobiologist who did not play a role in the study, confirmed the 2 million years of volcanic activity would have wreaked havoc for flora and fauna.
“This relatively long period of volcanic activity and environmental change would have had considerable consequences for animals on land. At this time, the dinosaurs had just begun to diversify, and it’s likely that without this event, they would never have reached their ecological dominance we see over the next 150 million years," Dunne said in a statement accompanying the study.
Several scientific understandings have been strengthened by the researchers' findings, Hilton said.
“Within the space of two million years the world’s animal and plant life underwent major changes including selective extinctions in the marine realm and diversification of plant and animal groups on land,” he said. “The main points of the study are that large igneous province volcanism can occur in distinct pulses, and that each pulse can individually affect the planet’s climates and environments.”
In an email, Dr. Jessica Whiteside, a scientist not involved in the study, described the conditions on Earth prior to the ascent of dinosaurs.
“We know that 40 million years before dinosaurs evolved, a long glacial epoch with polar ice caps ended. The ice cap-free time coincided with higher CO2 than today. Physical evidence of that ancient, pre-dinosaur ice age consists of grooved bedrock surfaces carved by glaciers and glacial sediments. Data for the lower CO2 comes from measuring the little holes in plant leaves that let CO2 in — the fewer the holes, the more CO2 — and from nodules of limestone that trap soil CO2 that seeps in from the atmosphere,” wrote Whiteside.
Over a shorter period thereafter, dinosaurs evolved and diversified.
“Within 20 million years, and against a backdrop of violently variable tropical conditions averaging between 122 and 140 degrees Fahrenheit, dinosaurs evolved and diversified into the three main groups: the meat-imbibing theropods, the long-necked, plant-guzzling sauropods and the beaked, herbivorous ornithischians,” added Whiteside.
Due to the extreme climate conditions of this era, dinosaurs relied on specific attributes and adaptations to endure and prosper.
“Dinosaurs had several key adaptations that possibly helped them to thrive in one of the most extreme periods of climate change the planet has seen up until now. These include the capability to stand upright, highly efficient “air-sac lungs," lungs that essentially run through the entire body, and downy features at least some point in their life history that might insulate them from temperature extremes,” wrote Whiteside.
According to Hilton, the study not only illuminates our understanding of Earth’s prehistoric conditions but also provides us with information that benefits our perspective on present-day climate change.
“This scale and duration of volcanism is much larger than anything we see on Earth at the present time, so this isn’t something that we need to worry about. But it is important as it shows how the planet responds to intense heating and changes to the carbon cycle with relevance to future human driven climate change,” said Hilton.
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