Study of tectonic plates may help scientists determine earthquake risks

February 22nd, 2008 - 2:53 pm ICT by admin  

Washington, Feb 22 (ANI): A new research by scientists regarding how tectonic plates move into the deepest reaches of the Earth, could potentially improve their ability to assess earthquake risks.

The research team, which comprised of scientists from UK and Switzerland, found that, contrary to common scientific predictions; dense plates tend to be held in the upper mantle, while younger and lighter plates sink more readily into the lower mantle.

The mantle is a zone underneath the Earth’s crust encompassing its super hot molten core.
It is divided into an upper and lower area, and is made up of a 2,900 km circumference of churning, viscous rock.

It is constantly fed with new material from parts of tectonic plates that slide down from the surface into it.

The researchers determined that old, dense and relatively stiff plates tend to flatten upon reaching the upper-lower mantle boundary, ‘draping’ on top of it.

By contrast, younger more malleable plates tend to bend and fold above the boundary of the lower mantle for tens of millions of years until they form a critical mass that can sink rapidly into the lower mantle.

When this mass moves into the lower mantle, the part of the plate still at the surface is pulled along at high speed. This explains why plate movements below Central and northern South America are much higher than expected for such young plates.

By using a numerical model, the team was able to build up a clear picture of how plates should move when stalled in the upper mantle and also show, for the first time, how tectonic plate rock is mixing within the mantle.

When two tectonic plates collide, with one sliding below the other and sinking into mantle, it can lead to the formation of mountain belts, like the Andes, and island arcs, like Japan and, in some places, cause explosive volcanism and earthquakes.

According to Dr Saskia Goes, from Imperial College London’s Department of Earth Science and Engineering, this study could potentially help scientists determine earthquake risks in parts of these zones where none have ever been recorded before.

“The speed with which the two plates converge, and the force with which they are pushed together, determine the size of the largest earthquakes and time between large tremors, said Goes.

Understanding what forces control the plate motions will ultimately help us determine the chances for large earthquakes in areas where plates converge, in places like the northern U.S., Java and northern Peru, but where no large earthquakes have been recorded in historic times,” she added. (ANI)

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