Nature

Pangaea Fell Victim to Its Own 'Game'

Supercontinent ate itself then broke up

By Gabriel Gache, Science News Editor

7th of July 2008, 09:58 GMT

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Nearly 300 million years ago, the world's last known supercontinent, Pangaea, started breaking up, eventually forming the seven continents we see today. Heat radiating from Earth's molten iron and nickel core is released to the outermost layers of the mantle through convection, which can also be held responsible for the sluggish movement of the plate tectonics, driving into and away from each other only to form a new supercontinent every few hundred million years or so and then breaking up again into smaller pieces.

How supercontinents form is pretty straightforward, although why and how they break up is not that clear. Recently, a team of researchers from the New York University proposed that the breaking up of supercontinents can be accounted for through a periodical alteration of the dynamics of so-called convection cells inside the Earth's mantle. According to their theory, once the supercontinent is formed, the heat convection patterns in the mantle change and the plate tectonics are forced to move away from each other, forming individual continents.

Now, Gabriel Gutierre-Alonso from the University of Salamanca proposes a model that approaches the problem of how Pangaea broke up through a mechanism called 'self-subduction', which may also explain some of the other problems regarding Earth's geology.

Subduction is the mechanism that allows plate tectonics to slip over and beneath one another as they push against each other. However, because Pangaea had a shape that allowed it to accommodate the Paleo-Tethys Ocean, it might have been possible that the southern region of the supercontinent suddenly started moving north, in order to close that gap. In the end, the southern shelf subducted under the north one.

"It's like a cat trying to bite its own tail," said geologist Fernando Corf￭ of the University of Oslo, co-author of the research.

As the southern end of the continent rushed to close the Paleo-Tethys Ocean, the central region of Pangaea would have started to compress, possibly forming what is now known as the Armorican Arc mountain range, covering the territory of today's Turkey, UK and Spain. At the same time, the side opposite to the Paleo-Tethys Ocean would have started to stretch and break up into a bicycle spoke pattern that formed ancient rifts similar to those in Norway and Madagascar.

TAGS:

Pangaea | supercontinent | convection | heat | plate tectonics

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