Monday, November 29, 1999

Split in Earth`s crust doesn`t always cause volcanic eruptions: Experts

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London, June 17 (ANI): New research reveals that when two parts of the Earth's crust break apart, this does not always cause massive volcanic eruptions.When the Earth's crust breaks into plates, these plates - constantly in motion - sometimes collide and fuse, or they can break apart to form new ones. When the latter plates break apart, a plume of hot rock can rise from deep within the Earth's interior, which can cause massive volcanic activity on the surface.Researchers had previously believed that only the temperature of the mantle beneath a plate determines the level of volcanic activity where a rift occurred. The new study reveals that in addition, the prior history of a rift also is also an important factor. In the case of the break-up of America from Europe, massive volcanic activity occurred along the rift because a previous geological event had thinned the plate, according to today's study. The thinned plate allowed the mantle underneath the plate to melt rapidly forming magma that erupted easily.In comparison, when India broke away from the Seychelles very little volcanic activity occurred along the North Indian Ocean floor, because the region had experienced volcanic activity in a neighbouring area called the Gop Rift 6 million years earlier. This exhausted the supply of magma and cooled the mantle, so that when a rift occurred, very little magma was left to erupt.The team discovered only small amounts of basalt rock, which is an indicator of earlier volcanic activity, below the ocean floor in the North Indian Ocean."Our study is helping us to see that the history of the rift is really important for determining the level of volcanic activity when plates break apart. We now know that this rift history is just as important as mantle temperature in controlling the level of volcanic activity on the Earth's surface," said Dr John Armitage, lead author of the paper from the Department of Earth Science and Engineering at Imperial College London.The study is published today in the journal Nature. (ANI)

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