A massive extinction at the end of the Triassic period was probably caused by the widespread volcanic eruptions at that time, clearing the way for the rise of more advanced dinosaurs. It’s a bold claim, but a team of American scientists headed up by Terrence Blackburn published new proof in Thursday’s online edition of Science.
As fossil hunters and dinosaurs fan are well aware, the end of the Triassic period came roughly 200 million years ago, when 76 percent of all water and land species died off in one of the top five largest extinction events known to have occurred on planet earth. That mass extinction cleared the path for the rise of the dinosaurs, who quickly took advantage of the open habitats to become the dominant land animals for 135 million years.
Every movie fan knows that dinosaurs went on to own the Jurassic period, but they ruled the Cretaceous as well.
Blackburn explained to Nature that many scientists had already suspected that the volcanic eruptions set off a chain of events that led to the Triassic extinctions. But his team’s new technique has allowed them to pin down the timing. After dating the fossil lava in both North America and Morocco, he said that the first and most explosive eruptions seem to have triggered the mass dying.
The eruptions started in Morocco over 200 million years ago and spread to the US east coast region within 12,000 years. At that time, the eastern seaboard and Africa were joined as part of the ancient supercontinent called Pangaea. Indeed, it’s the volcanic rift that split the two continents which was also responsible for the deadly string of eruptions.
There are still some details that need to be worked out. Volcanoes going off all over the place are decidedly unpleasant, but how would they wipe out entire species rather than individuals and populations near the eruptions?
University of Copenhagen scientists offered a complex explanation in 2011. “There was a release of CO2 from volcanic eruptions that warmed up global temperatures and also the ocean,” Micha Ruhl told The New York Times. “Methane is only stable under certain temperatures. If it gets warm, it is released.”
Ruhl proposed that the volcanoes warmed up the planet to the point where the oceans released 12,000 gigatons of methane into the air. Methane is an even more powerful greenhouse gas than carbon dioxide, so the inevitable result was runaway global warming and mass extinction of species that couldn’t adapt fast enough.
But that’s only one theory. What do you think caused the Triassic extinction volcanoes to clear the way for the iconic Jurassic dinosaurs? I’m still wondering.
[Dienonynchus skeleton photo courtesy Elaine Radford]
[Triceratops vs. Tyrannosaurus rex image courtesy Marcin Chady and Wikipedia Commons]