Superplumes deep within Earth may have shaped the continents

December 16th, 2008 - 2:05 pm ICT by ANI  

Washington, Dec 16 (ANI): Scientists have found that two superplumes of hot rock deep within the Earth are linked to the plate motions that shape the continents.

The two giant plumes, one beneath Hawaii and the other beneath Africa, have likely existed for at least 200 million years, according to Wendy Panero, assistant professor of earth sciences at Ohio State University.

The giant plumes, or superpiles as Panero calls them, rise from the bottom of Earths mantle, just above our planets core.

Each is larger than the continental United States, and each is surrounded by a wall of plates from Earths crust that have sunk into the mantle.

Computer models have connected the piles to the sunken former plates, but it’’s currently unclear which one spawned the other.

Plates sink into the mantle as part of the normal processes that shape the continents.

Do these superpiles organize plate motions, or do plate motions organize the superpiles? I dont know if its truly a chicken-or-egg kind of question, but the locations of the two piles do seem to be related to where the continents are today, and where the last supercontinent would have been 200 million years ago, Panero said.

That supercontinent was Pangea, and its breakup eventually led to the seven continents we know today.

Scientists first proposed the existence of the superpiles more than a decade ago.

The presence of the superpiles and the location of subducted plates suggest that the two superpiles have likely remained fixed to the Earths core while the rest of the mantle has churned around them for millions of years.

But to date, the seismic images have created a mystery: they suggest that the superpiles have remained in the same locations, unchanged for hundreds of millions of years.

Unlocking this mystery is the goal of the Cooperative Institute for Deep Earth Research (CIDER) collaboration.

They have assembled a new model that suggests why the two superpiles are so stable, and what they are made of.

As it turns out, just a tiny difference in chemical composition can keep the superpiles in place, they found.

The superpiles contain slightly more iron than the rest of the mantle; their composition likely consists of 11-13 percent iron instead of 10-12 percent. But, that small change is enough to make the superpiles denser than their surroundings.

According to Panero, Material that is more dense is going to sink to the base of the mantle. It would normally spread out at that point, but in this case, we have subducting plates that are coming down from above and keeping the piles contained. (ANI)

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