Warming can affect plate tectonics

Times of India , Friday, October 17, 2008
Correspondent : ANI
WASHINGTON: New evidence has emerged that, given enough time, climate change can even alter the course of plate tectonics, by grinding them down.

The march of plate tectonics had previously seemed impervious to water and air’s fickle motions. No matter the weather, plates would grind past and crash into one another to build mountain ranges, or sink into the hot depths of the mantle.

But, according to Brendan Meade of Harvard University, the mighty Andes mountain range, the longest on Earth, might not be here today if it wasn’t for a drastic shift in climate 14 million years ago.

Over 7,000km long, the Andes are the result of the dense Nazca plate moving eastward from the Pacific Ocean and diving underneath the South American plate.

The collision creates nonstop earthquakes, volcanic eruptions and dramatic uplift that has thrust the Andes as high as the towering summit of Aconcagua, 6,962m above sea level. Nothing outside of Asia is taller.

But, the mountains are young. Until 15 million years ago the Andes had never grown higher than 1,500m. Then the climate changed.

"Back then, the Nazca and South American plates were converging at a rate of around 15cm per year,” Meade said. That is far faster than the rate at which the Indian and Eurasian plate are colliding to form the Himalayas today. “But it was soaking wet. Then, all of a sudden, there was this aridification,” said Meade.

Climate studies of the period show that the Andes region was a rainforest until 15 million years ago. Annual precipitation suddenly dropped from 2m to 20mm, reshaping the landscape into the parched desert it is today.

The lack of rain would have greatly reduced erosion, Meade and co-author Clinton Conrad of the University of Hawaii reason, allowing the young, humble Andes to rise to prominence.

 
SOURCE : Friday, 17 October 2008
 


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