Giant Crack In Africa May Create A New Ocean

A 35 mile rift in the desert of Ethiopia is one manifestation of a rift that may eventually give rise to a new ocean, scientists say. The crack, 20 feet wide in spots, opened in
giant crack in africa may create a new ocean -...
PTI November 06, 2009 10:14 IST

A 35 mile rift in the desert of Ethiopia is one manifestation of a rift that may eventually give rise to a new ocean, scientists say.

The crack, 20 feet wide in spots, opened in 2005 and some geologists believed then that it would spawn a new ocean. But that view was controversial, and the rift had not been well studied.

A new study involving an international team of scientists and reported in the journal Geophysical Research Letters finds the processes creating the rift are nearly identical to what goes on at the bottom of oceans, further indication a sea is in the region's future.

The same rift activity is slowly parting the Red Sea, too.

Using newly gathered seismic data from 2005, researchers reconstructed the event to show the rift tore open along its entire 35-mile length in just days. Dabbahu, a volcano 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, the researchers explained in a statement  on Wednesday.

"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," said Cindy Ebinger, professor of earth and environmental sciences at the University of Rochester and co-author of the study.

The result shows that highly active volcanic boundaries along the edges of tectonic ocean plates may suddenly break apart in large sections, instead of in bits, as the leading theory held. And such sudden large-scale events on land pose a much moreserious hazard to populations living near the rift than would several smaller events, Ebinger said.

"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," says 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."

The African and Arabian plates meet in the remote Afar desert of Northern Ethiopia and have been spreading apart in a rifting process — at a speed of less than 1 inch per year — for the past 30 million years.

This rifting formed the 186-mile Afar depression and the Red Sea. The thinking is that the Red Sea will eventually pour into the new sea in a million years or so. The new ocean would connect to the Red Sea and the Gulf of Aden, an arm of the Arabian Sea between Yemen on the Arabian Peninsula and Somalia in eastern Africa.

Atalay Ayele, professor at the Addis Ababa University in Ethiopia, led the investigation, gathering seismic data with help from neighboring Eritrea and Ghebrebrhan Ogubazghi, professor at the Eritrea Institute of Technology, and from Yemen with the help of Jamal Sholan of the National Yemen Seismological Observatory Center. 

The crack in the Earth's crust – which could be the forerunner to a new ocean – ripped open in just days in 2005, the new study suggests.

The opening, located in the Afar region of Ethiopia, presents a unique opportunity for geologists to study how mid-ocean ridges form.

The crack is the surface component of a continental rift forming as the Arabian and African plates drift away from one another. It began to open up in September 2005, when a volcano at the northern end of the rift, called Dabbahu, erupted.

The magma inside the volcano did not reach the surface and erupt as a fountain of lava – instead, it was diverted into the continental rift underground. The magma cooled into a wedge-shaped "dike" that was then uplifted, rupturing the surface and creating a 500-metre-long, 60-metre-deep crack.

Using sensor data collected by universities in the region, researchers led by Atalay Ayele of Addis Ababa University in Ethiopia reconstructed the sequence of seismic events that led to the crack's formation. They found that a 60-kilometre-long, 8-metre-wide dike of solidified magma formed in the rift, causing the crack, in a matter of days.

The rift began when Mount Dabbahu erupted, for the first time in recorded history, and in a matter of just three weeks spread to up to 25' wide along a fault line in the Afar desert. Heading towards the Red Sea, it could eventually split off Eritrea, Djibouti and part of Ethiopia from the rest of the continent.

The location of the start of the rift is marked as 'A' in this image from Google Maps.

Rather than opening up in a series of small earthquakes, magma was pushed up in the middle of the rift and the whole thing began "unzipping" in either direction.

Report co-author Cindy Ebinger of the University of Rochester said, "We know that seafloor ridges are created by 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."In all, the processes at work here are "nearly identical to those at the bottom of the world's oceans" the report said.


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