June 16, 2009

Experts Say Andes Mountain Range Is Shrinking

Argentine researchers suggest that the Andes, the largest mountain chain on the American continent, are losing altitude in some areas, BBC News reported.

Parts of the Andes are undergoing a cycle of collapse that started some 6 million years ago, according to Folguera Andres and Victor Ramos, geologists in the Faculty of Natural Sciences at the University of Buenos Aires (UBA).

The Argentine provinces of Mendoza and Neuquen have been showing a reduction in height over the years; but elsewhere, such as in San Juan, the mountain chain is actually growing.

The Andes, which border the Pacific Ocean for some 4,600 miles, are relatively young compared to most of the world's mountain ranges.

"The Andes are alive," Andres said. He added that the shifting Andes are a product of subduction. These subduction zones are areas where one of the Earth's tectonic plates sinks beneath another, generating huge forces.

These zones are also the origin points of some of the largest and most destructive earthquakes on the planet, when parts of the two plates stick to each other causing a sudden release of stress.

The bottom of the Pacific Ocean supports, at a strange angle, the continental shelf on which the Andes rest.

Andres said the Andes were formed because the bottom of the Pacific Ocean went under the South American continent at an angle of approximately 30 degrees on average.

"But there are some places where the ocean floor goes in horizontally, increasing the friction and pushing up the mountain range above, as at the Cordillera Blanca of Peru," he said.

However, the ocean floor begins to slide under the continental shelf at an angle every 5 to 10 million years, causing the mountain range above it to crumble.

Therefore, in theory, the Andes could disappear in time.

Andres said that before the Andes were formed there were numerous Andean chains that ran along the edge of South America and many of those chains suffered cycles of collapse.

These mountains sometimes collapsed into the sea, such as in the formation of the Drake Passage, the stretch of water that separates the American continent and Antarctica, which happened 26 million years ago.

The reverse process could generate the largest mountain in America, according to several theories.

But Andres says that the process of gravity makes it unlikely that any mountain higher than 26,000 feet can be formed.

Either way, the results will not be seen for another 20 or 30 million years; and by that time, geologists say man will have evolved into another species.


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