Australian discovery solves mystery of the Andes

Mar 14, 2007

A research team led by an ANU scientist has solved the mystery behind the formation of the Andes by discovering how the jostling of tectonic plate boundaries affects geological formations.

It’s been known for some time that the Andes mountain range in South America sits above a subduction zone, where one tectonic plate is sinking below its neighbouring plate. But until now, it hasn’t been clear how such a movement could result in the upward thrust that created the Andes.

The researchers’ findings were published in Nature today.

“It’s commonly understood that large mountain ranges occur when one continent collides with another,” explained team leader Dr Wouter Schellart from the Research School of Earth Sciences. “This kind of collision is responsible for the Himalayas, which have resulted from the Indian continent pushing up into Asia. But there’s no continent butting up against South America, so we needed to find a different explanation for the Andes.”

Using the modelling power of supercomputers, Dr Schellart and his colleagues Dr Justin Freeman at ANU and Dr Dave Stegman, Professor Louis Moresi and Mr David May at Monash University in Melbourne discovered that just as tectonic plates move, so too do the boundaries between them. As a subducting plate is drawn downward by gravity, it forces the boundary between the subducting plate and overriding plate to move. This means the boundaries between tectonic plates are constantly changing shape.

The researchers found that the width of the tectonic boundary determines the speed and direction of its migration, which will effect whether a mountain range or an ocean basin forms above the activity. They also found that the width determines the shape of subduction zones, which thereby explains the curvature of deep ocean trenches that mark the surface expression of these subduction zones.

“So in the southwest Pacific, near New Zealand, the tectonic boundary is moving backwards very fast, in this case back towards the east. That causes the overriding plate to extend and form a deep basin,” Dr Schellart said. “But along the west coast of South America, the boundary is not moving backward very fast, and in the centre it’s actually moving forward very slowly. The overriding plate is moving toward the boundary itself. Hence you get compression, and the formation of the Andes.”

Dr Schellart said the tectonic boundary at the Andes can support such compressive behaviour because the zone is the widest of its kind on the planet, running for some 7,400 km. If the boundary fragmented, the upward thrust of the Andes would cease. But the team’s models predict that the world’s longest mountain range is likely to continue its upward thrust for thousands of years.

Source: Australian National University

Explore further: Magnitude-7.2 earthquake shakes Mexican capital

add to favorites email to friend print save as pdf

Related Stories

Off-rift volcanoes explained

Mar 23, 2014

Volcanoes often develop outside the rift zone in an apparently unexpected location offset by tens of kilometers has remained unanswered. An international team of scientists has shown that the pattern of stresses ...

Earth's mantle plasticity explained

Mar 07, 2014

Earth's mantle is a solid layer that undergoes slow, continuous convective motion. But how do these rocks deform, thus making such motion possible, given that minerals such as olivine (the main constituent ...

New study reveals insights on plate tectonics

Mar 04, 2014

(Phys.org) —The Earth's outer layer is made up of a series of moving, interacting plates whose motion at the surface generates earthquakes, creates volcanoes and builds mountains. Geoscientists have long ...

Recommended for you

Magnitude-7.2 earthquake shakes Mexican capital

Apr 18, 2014

A powerful magnitude-7.2 earthquake shook central and southern Mexico on Friday, sending panicked people into the streets. Some walls cracked and fell, but there were no reports of major damage or casualties.

User comments : 0

More news stories

China says massive area of its soil polluted

A huge area of China's soil covering more than twice the size of Spain is estimated to be polluted, the government said Thursday, announcing findings of a survey previously kept secret.

UN weather agency warns of 'El Nino' this year

The UN weather agency Tuesday warned there was a good chance of an "El Nino" climate phenomenon in the Pacific Ocean this year, bringing droughts and heavy rainfall to the rest of the world.