Volcanoes played pivotal role in ice age that caused mass extinction 450 mln yrs ago
27 Oct 2009, 1344 Hrs

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Washington, October 27 Scientists have discovered that volcanoes played a pivotal role in a deadly ice age 450 million years ago that ultimately killed two-thirds of all species on the planet.

These volcanoes first caused global warming - by releasing massive amounts of carbon dioxide into the atmosphere.

When they stopped erupting, Earth's climate was thrown off balance, and the ice age began.

"The discovery underscores the importance of carbon in Earth's climate today," said Matthew Saltzman, associate professor of earth sciences at Ohio State University.

Previously, Saltzman and his team linked this same ice age to the rise of the Appalachian Mountains.

As the exposed rock weathered, chemical reactions pulled carbon from Earth's atmosphere, causing a global cooling which ultimately killed two-thirds of all species on the planet.

Now, the researchers have discovered the other half of the story: giant volcanoes that formed during the closing of the proto-Atlantic Ocean - known as the Iapetus Ocean - set the stage for the rise of the Appalachians and the ice age that followed.

"Our model shows that these Atlantic volcanoes were spewing carbon into the atmosphere at the same time the Appalachians were removing it," Saltzman explained.

"For nearly 10 million years, the climate was at a stalemate. Then, the eruptions abruptly stopped, and atmospheric carbon levels fell well below what they were in the time before volcanism. That kicked off the ice age," he said.

This is the first evidence that a decrease in carbon from volcanic degassing - combined with continued weathering of the Appalachians - caused the long-enigmatic glaciation and extinction in the Ordovician period.

According to scientists, 460 million years ago, during the Ordovician, volcanoes along the margin of what is now the Atlantic Ocean spewed massive amounts carbon dioxide into the atmosphere, turning the world into a hothouse.

Lava from those volcanoes eventually collided with North America to form the Appalachian Mountains.

By 445 million years ago, glaciers had covered the south pole on top of the supercontinent of Gondwana, which would eventually break apart to form the continents of the southern hemisphere.

Two-thirds of all species had perished.

"Knowing these details can help us understand how carbon in the atmosphere is changing Earth's climate today," said Saltzman. (ANI)

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