Mega-eruptions Caused Mass Extinction, Study Finds - 0 views
-
In a new study published today in the journal Science, researchers say they have confirmed that eruptions large enough to bury the U.S. under 300 feet (91 meters) of lava occurred at the same time that vast numbers of plant and animal species disappeared from the fossil record. About 201 million years ago, tectonic forces started ripping the supercontinent known as Pangaea apart, said Terrence Blackburn, a geologist at the Carnegie Institution for Science in Washington, D.C., and lead author of the study. The underlying mantle rock melted, generating these large eruptions, he added. The rift, which eventually created the Atlantic Ocean basin, happened between sections of Pangaea that would go on to become North America and Africa. (Read about how Pangaea formed.)
-
by using a rare mineral called zircon, found in igneous rocks like basalts, the researchers were able to narrow down their margin of error to 20,000 to 30,000 years—pegging the initial eruptions to just before the mass extinction event. “Zircon is a perfect time capsule for dating those rocks,” said Blackburn. When the mineral crystallizes, it incorporates uranium, which decays over a known time with respect to the element lead. By measuring the ratio of uranium to lead in our samples, we can determine the age of those crystals, he explained.
-
There is evidence that the initial volcanic eruptions doubled the amount of the carbon dioxide in the atmosphere, which led to increased global temperatures and ocean acidification, he noted. This happened quickly, which probably didn’t give organisms at the time much of a chance to adjust to the changes.
- ...3 more annotations...
-
There is one case 65 million years ago, at a point in time known as the Cretaceous-Tertiary boundary (K-T boundary), with strong evidence supporting an asteroid impact around the same time the dinosaurs disappeared.
-
“That one instance really guided everybody’s thinking, and the idea that impacts caused mass extinctions was really, really popular,” said Renne, who wasn’t involved in the Blackburn study.
-
enne says that even the asteroid impact at the K-T boundary likely only finished the job that major volcanic eruptions in India started. (Related: “What Killed Dinosaurs: New Ideas About the Wipeout.”)