Hot volcanic mantle rock that lies beneath Africa is trying to split the continent apart and could eventually create a new ocean. ?The Ethiopian rift is one of the few places in the world where we can see the transition from continental rifting to something that looks more oceanic,? says Dr. Cindy Ebinger. ?It?s a unique area worldwide.?
The crack in the Earth?s surface runs from Malawi in the South, through Tanzania, Kenya and Ethiopia, to the Red Sea and the Gulf of Aden. Deep inside the Earth, there?s a huge plume of warm soft mantle rock rising diagonally and running up beneath Southern Africa towards the Afar region of Ethiopia. This super-plume, as it?s called, may be responsible for the high elevation of much of Southern and Eastern Africa. It may also be the cause of the line of volcanoes that runs up the Great Rift Valley, including Mount Nyiragongo, which recently sent red-hot lava into the town of Goma in the Congo.
For most of its length the East African rift valley is just an ordinary rift, running through a continent. But as it gets further north, it forms a line of cracks along which volcanic magma rises to create the floor of an ever widening sea. In Ethiopia it is in transition between the two forms and this gives geologists a chance to see how a new ocean forms.
Project Eagle (Ethiopian Afar Geophysical Lithospheric Experiment) wants to use seismometers to record natural earth tremors and the vibrations from explosive charges detonated in boreholes. The seismic waves travel at different speeds through rocks of different temperatures and densities. Ebinger and her colleagues want to find reservoirs of hot, molten magma within the crust that could feed future volcanoes. ?There are several dormant volcanoes but there has never been a study to monitor volcanoes in the rift,? she says. ?These are dangerous because the lava has more silica in it and is resistant to flow, so these are explosive eruptions that can cause death and damage to a large region.?
So far, the test show that a mantle plume alone is not enough to open an ocean. There needs to be a sideways pull to divide the continent, allowing the hot magma to rise underneath to fill the gap and form the floor of the new ocean. Scientists aren?t sure whether that will actually happen along the East African rift. With the Atlantic Ocean still opening and pushing on Africa from the west and India still colliding with Asia and the Indian Ocean opening to the east, there may be nowhere for the rift to expand.
Professor Peter Maguire, of Leicester University in the U.K. is one scientist who believes there will be a new ocean in the area someday. ?We do believe that we are on the transition from continental to oceanic rifting,? he says. ?The continent in the northern part of Ethiopia is separating and there will be an ocean penetrating down into East Africa.?
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