Page last updated at 10:43 GMT, Tuesday, 16 June 2009 11:43 UK

'Teenage' Andes could collapse

By Veronica Smink
BBC Mundo

Andes from a plane
Growing pains for "young" Andes mean they could actually shrink

The Andes were formed 120 million years ago; but in geological terms, this giant of South America is more like a teenager going through growth problems.

A new study by a group of Argentine researchers suggests that the largest mountain chain on the American continent is not as quiet as it seems.

According to Folguera Andres and Victor Ramos, geologists in the Faculty of Natural Sciences at the University of Buenos Aires (UBA), some mountains are losing altitude.

"We found that parts of the Andes are undergoing a cycle of collapse which started some 6 million years ago," says Mr Andres.

The reduction in height is taking place in the Argentine provinces of Mendoza and Neuquen, but elsewhere the mountain chain is actually growing, for example in San Juan.

The Andes are alive
Folguera Andres

Most of the world's mountain ranges are older than the Andes, which border the Pacific Ocean for some 7,500 km.

"The Andes are alive," says Mr Andres.

The shifting Andes are a product of subduction.

Subduction zones are areas where one of the Earth's tectonic plates sinks beneath another, generating huge forces.

The sites are also where the largest and most destructive earthquakes on the planet occur when there is a sudden release of the stress produced when parts of the two plates stick to each other.

Deep underground, the floor of the Pacific Ocean supports the continental shelf on which the Andes rest: but at a strange angle.

"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," says Mr Andres.

"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".

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

Disappearing Andes?

In theory the Andes could disappear.

"Before the Andes were formed there were numerous Andean chains that ran along the edge of South America and many of these chains suffered cycles of collapse," says Mr Andres.

Sometimes these mountains collapsed into the sea; a process that 26m years ago led to the formation of the Drake Passage, the stretch of water that separates the American continent and Antarctica.

In theory, the reverse process could generate the largest mountain in America.

However, Mr Andres says that the process of gravity makes it unlikely that any mountain higher than 8km can be formed.

Whatever happens the results will not be seen for another 20m or 30m years, "by which time man will have evolved into another species," according to the geologist.

Print Sponsor


Has China's housing bubble burst?
How the world's oldest clove tree defied an empire
Why Royal Ballet principal Sergei Polunin quit


Sign in

BBC navigation

Copyright © 2020 BBC. The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.

Americas Africa Europe Middle East South Asia Asia Pacific