Continent Splits Apart

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A Continent Splits ApartBy Axel Bojanowski http://service.spiegel.de/cache/international/spiegel/0,1518,405947,00.htmlNormally new rivers, seas and mountains are born in slow motion. The AfarTriangle near the Horn of Africa is another story. A new ocean is formingthere with staggering speed -- at least by geological standards. Africa willeventually lose its horn.Geologist Dereje Ayalew and his colleagues from Addis Ababa University wereamazed -- and frightened. They had only just stepped out of their helicopteronto the desert plains of central Ethiopia when the ground began to shakeunder their feet. The pilot shouted for the scientists to get back to thehelicopter. And then it happened: the Earth split open. Crevices beganracing toward the researchers like a zipper opening up. After a few seconds,the ground stopped moving, and after they had recovered from their shock,Ayalew and his colleagues realized they had just witnessed history. For thefirst time ever, human beings were able to witness the first stages in thebirth of an ocean.Normally changes to our geological environment take place almostimperceptibly. A life time is too short to see rivers changing course,mountains rising skywards or valleys opening up. In north-eastern Africa'sAfar Triangle, though, recent months have seen hundreds of crevicessplitting the desert floor and the ground has slumped by as much as 100meters (328 feet). At the same time, scientists have observed magma risingfrom deep below as it begins to form what will eventually become a basaltocean floor. Geologically speaking, it won't be long until the Red Seafloods the region. The ocean that will then be born will split Africa apart.The Afar Triangle, which cuts across Ethiopia, Eritrea and Djibouti, is thelargest construction site on the planet. Three tectonic plates meet therewith the African and Arabian plates drifting apart along two separate faultlines by one centimeter a year. A team of scientists working with ChristopheVigny of the Paris Laboratory of Geology reported on the phenomenon in a2006 issue of the Journal of Geophysical Research. While the two plates moveapart, the ground sinks to make room for the Red Sea and the Gulf of Aden. A third crevice cuts south, splitting not far from Lake Victoria. One branchof the rift runs to the east, the other to the west of the lake. The twobranches of this third crevice are moving apart by about one millimeter ayear.The dramatic event that Ayalew and his colleagues witnessed in the AfarDesert on Sept. 26, 2005 was the first visual proof of this process -- andit was followed by a week-long series of earthquakes. During the months thatfollowed, hundreds of further crevices opened up in the ground, spreadingacross an area of 345 square miles. "The earth has not stopped movingsince," geophysicist Tim Wright of the University of Oxford says. The groundis still splitting open and sinking, he says; small earthquakes areconstantly shaking the region. Scientists have made repeated trips to the area since the drama of lastSeptember. Locals have reported a number of new cracks opening in theground, says geologist Cynthia Ebinger from the University of London, andduring each visit, new crevices are discovered. Fumes as hot as 400 degreesCelsius (752 degrees Fahrenheit) shoot up from some of them; the sound ofbubbling magma and the smell of sulphur rise from others. The largercrevices are dozens of meters deep and several hundred meters long. Tracesof recent volcanic eruptions are also visible.In a number of places, cracks have opened up beneath the thin layer ofvolcanic ash that covers the region. As there is no ash in the fissures,it's clear that they opened up after the volcanic eruptions, most of whichtook place at the end of September or in October, 2005. A number of localswho fled the eruptions have reported that a black cloud of ash -- spewed outof the Dabbahu volcano -- darkened the sky for three days.A new ocean floor on the Earth's surfaceBasalt magma has risen into some of the crevices. For the moment, Ayalewexplains, the lava seems not to be rising further. A number of recenteruptions, though, have left layers of new basalt lava on the Earth'ssurface. And it's the exact same kind of lava that spews out of volcanicridges deep under the ocean -- a process which slowly pushes older lavasediments away on either side. The process has only just begun in the AfarTriangle -- and scientists for the first time can witness the birth of a newocean floor.The source of the African magma looks to be a gigantic stream of molten rockrising from beneath the Earth's crust and slicing through the Africancontinental plate like a blow torch. It's a process that began thirtymillion years ago when lava broke through the continent for the first time,separating the Arabian Peninsula from Africa and creating the Red Sea.Now, it's the Afar Triangle's turn and it's sinking rapidly. Large areas arealready more than 100 meters (328 feet) below sea level. For now, thehighlands surrounding the Denakil Depression prevent the Red Sea fromflooding these areas, but erosion and tectonic plate movement arecontinually reducing the height of this natural barrier. The DenakilDepression, which lies to the east of Afar, is already prey to regularfloods -- each flood leaving behind a crust of salt.Africa to lose its hornThe chain of volcanoes that runs along the roughly 6,000 kilometer (3,730mile) long East African Rift System offers further testimony to the breakingapart of the continent. In some areas around the outer edges of the RiftSystem, the Earth's crust has already cracked open, making room for themagma below. From the Red Sea to Mozambique in the south, dozens ofvolcanoes have formed, the best known being Mt. Kilimanjaro and Mt.Nyiragongo. These fiery mountains too will one day sink into the sea. Geophysicists havecalculated that in 10 million years the East African Rift System will be aslarge as the Red Sea. When that happens, Africa will lose its horn. : Blogs discussing this story<http://technorati.com/search/http://service.spiegel.de/cache/international/ spiegel/0,1518,405947,00.html?partnerid=160>