Thursday, January 7, 2010

New ocean to split Ethiopia

Afrol News, 5 November 2009

Since a gigantic rift broke open the desert ground in Ethiopia in 2005, scientists have speculated the rift was the first step in a process that will split eastern Ethiopia and Somalia from the African continent by a new ocean. Now, they have found proof it indeed will.

As the 56 kilometres large rift was created in 2005, it went almost un-noted due to the sparse population in the Ethiopian desert, but satellite images clearly showed the landscape had changed. At the time, many geologists believed the rift was the beginning of a new ocean as two parts of the African continent pulled apart, but the claim was controversial.

Now, scientists from several countries have confirmed that the volcanic processes at work beneath the Ethiopian rift are nearly identical to those at the bottom of the world's oceans, and the rift is indeed likely to be the beginning of a new sea.

A new study, published in the latest issue of 'Geophysical Research Letters', suggests that the highly active volcanic boundaries along the edges of tectonic ocean plates may suddenly break apart in large sections, instead of little by little as has been predominantly believed. In addition, such sudden large-scale events on land pose a much more serious hazard to populations living near the rift than would several smaller events, says Cindy Ebinger, professor at the University of Rochester (US) and co-author of the study.

"The whole point of this study is to learn whether what is happening in Ethiopia is like what is happening at the bottom of the ocean where it's almost impossible for us to go," adds Ms Ebinger. "We knew that if we could establish that, then Ethiopia would essentially be a unique and superb ocean-ridge laboratory for us. Because of the unprecedented cross-border collaboration behind this research, we now know that the answer is yes, it is analogous."

Atalay Ayele, professor at the Addis Ababa University in Ethiopia, led the investigation, painstakingly gathering seismic data surrounding the 2005 event that led to the giant rift opening more than 30 kilometres in width in just days.

Along with the seismic information from Ethiopia, Mr Ayele combined data from neighbouring Eritrea with the help of Ghebrebrhan Ogubazghi, professor at the Eritrea Institute of Technology, and from Yemen with the help of Jamal Sholan of the National Yemen Seismological Observatory Centre. The map he drew of when and where earthquakes happened in the region fit tremendously well with the more detailed analyses Ms Ebinger had conducted in more recent years.

Mr Ayele's reconstruction of events showed that the rift did not open in a series of small earthquakes over an extended period of time, but tore open along its entire 56-kilometre length in just days. A volcano called Dabbahu at the northern end of the rift erupted first, then magma pushed up through the middle of the rift area and began "unzipping" the rift in both directions, says Ms Ebinger.

Since the 2005 event, Ms Ebinger and her colleagues have installed seismometers and measured 12 similar - though dramatically less intense - events.

"We know that seafloor ridges are created by a similar intrusion of magma into a rift, but we never knew that a huge length of the ridge could break open at once like this," says Ms Ebinger.

She explains that since the areas where the seafloor is spreading are almost always situated under miles of ocean, it is nearly impossible to monitor more than a small section of the ridge at once so there is no way for geologists to know how much of the ridge may break open and spread at any one time. "Seafloor ridges are made up of sections, each of which can be hundreds of miles long. Because of this study, we now know that each one of those segments can tear open in a just a few days."

Mr Ayele and his colleagues are continuing to monitor the area in Ethiopia to learn more about how the magma system beneath the rift evolves as the rift continues to grow.

None of the researcher however expects to observe the separation of Ethiopia in their lifetimes. The creation of a new seafloor happens at the speed of millions of years. But if the geological processes now active in Ethiopia remain in place, what is now the African Horn - and maybe even parts of Kenya - will one day become an island continent on its own. It is for our ancestors to see.