Continental Clash Cooled The Climate

From Science News:

The collision between India and Asia set off events that likely caused long-term cooling in Earth’s climate

When the tectonic plate carrying India slammed into Asia about 50 million years ago, the ensuing geological changes triggered a long-term cooling trend. That trend later enabled Antarctic ice sheets to grow, a new study suggests.

Before the collision, volcanoes along the rim of southern Asia spewed immense quantities of carbon dioxide into the atmosphere. Much of that planet-warming greenhouse gas came from seafloor, carbonate-rich sediments that were shoved below Asia by tectonic movements, says Dennis V. Kent, an earth scientist at Rutgers University in Piscataway, N.J. Carbon in those sediments soon reappeared in the atmosphere as the carbon dioxide spewing from volcanoes. When the India-Asia collision removed those seafloor sediments, that source of carbon dioxide disappeared, Kent and his colleagues argue in an upcoming Proceedings of the National Academy of Sciences.

Simultaneously, erosion of rocks on the Indian subcontinent — in particular, the chemical weathering of a large amount of basaltic rocks formed from volcanic eruptions just a few million years earlier — consumed large volumes of carbon dioxide. That double whammy, the researchers speculate, caused atmospheric concentrations of carbon dioxide to plummet, cooling Earth significantly.

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