Mega-volcanic eruptions linked to pre-dinosaur extinction

Delila James | @@delilalaw| March 22, 2013

Mega-volcanic eruptions linked to pre-dinosaur extinction

Scientists link mass extinctions with massive die-offs.

Scientists have discovered a strong link between mega-volcanic eruptions and massive pre-dinosaur extinctions, the first such evidence of massive die-offs preceding the age of the dinosaurs.

Examining global evidence from New Jersey to North Africa, a new study ties the abrupt disappearance of approximately half of Earth’s species to a series of massive volcanic cataclysms that took place nearly 200 million years ago.

“This may not quench all the questions about the exact mechanism of the extinction itself.” said the study’s coauthor Paul Olson, a geologist at Columbia University’s Lamont-Doherty Earth Observatory. “However, the coincidence in time with the volcanism is pretty much ironclad.”

Scientists say gases released during the End-Triassic Extinction (ETE) may have led to sudden and dramatic extinctions, partly a result of climate changes. The vast die-off may have paved the way for dinosaurs to evolve and dominate the planet for the next 135 million years.

Although many researchers have suggested that the ETE and at least four other known past extinctions were caused in part by mega-volcanism and the resulting climate change, they had previously been unable to show that the extinctions occurred during the time of discovered geological deposits. Geologists say the latest study provides the necessary link between these two phenomena, showing the date for the ETE — 201,564,000 years ago — happened precisely at the same time as a colossal outpouring of lava.

The eruptions, known as the Central Atlantic Magmatic Province (CAMP), began when land on Earth was part of one enormous supercontinent known as Pangaea. The massive eruptions began around 200 million years ago, lasting more than 600,000 years and creating a rift that ultimately became the Atlantic Ocean.

Lead author of the study, Terrence Blackburn of the Carnegie Institution, used the decay of uranium isotopes to pull exact dates from basalt, a rock known to been left by eruptions. Researchers analyzed samples from Nova Scotia, Morocco, and even the suburbs of New York City.

Until now, the margin of error in calculating the timing of these eruptions ranged between one to three million years. However, by using a rare mineral called zircon — found in igneous rocks such as basalt — scientists were able to narrow down their margin of error to 20,000 to 30,000 years, tying 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.”

The study is published in the journal Science.

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