African Rift Creation Observed: New Aqua Landscape Predicted
In 2005, a volcano eruption in the northeast corner of the African continent created a land feature that was once assumed to take millions and millions of years to form.
Geologists generally assumed that large cracks in the Earth's crust form when two techtonic plates move over each other, and at a pace of less than an inch per year, creates a depression that would eventually fill with water to form a sea or ocean. This process was thought to take at least tens of millions of years.
A map showing Dabbahu volcano in the Afar triangle, along with epicenters from the earthquake swarm of 14 September to 4 October 2005 The solid triangles indicate Holocene volcanoes, although the one for Dabbahu is swamped by the pattern of epicenters. The Alayta shield volcano (labeled "A") sits 32.7 km NNE of Dabbahu's summit and erupted several times in the early 1900's. Epicenters were compiled from the U.S. Geological Survey (USGS) National Earthquake Information Center website. Image Credit: U.S. Geological Survey (USGS) National Earthquake Information Center
This depression, crack, or rift in the Earth's crust created by a volcano named Dabbahu, located in the northern part of Ethiopia, formed when it began to erupt and push magma up through the landscape, effectively unzipping a large portion of this Oblate Spheroid in just days. This rift has now grown to be measured at about 35 miles long and as wide as 20 feet and is expected to become an ocean or sea in about one million years.
Feleke Worku, a surveyor from the Ethiopian Mapping Agency, examines a ground rupture created during the September 2005 rifting event. Image Credit: Tim Wright, University of Leeds
This excerpted and edited from Life Science -
Giant Crack in Africa Will Become New Ocean
Life Science, Tuesday, November 03, 2009
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 new sea is in the region's future.
The same rift activity is slowly parting the Red Sea, too.
A red thumbtack locates Dabbahu, a volcano at the northern end of a rift geophysicists say will become an ocean. Image Credit: Google Maps
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 today.
"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 more serious hazard to populations living near the rift than would several smaller events, Ebinger said.
Looking NNW from the central part of the Dabbahu rift segment towards the Dabbahu volcano (~30 km away). Image Credit: Cindy Ebinger, University of Rochester, USA
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 body of water 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.
Central section of 60 km-long rift zone that opened south of Dabbahu volcano. Image Credit: Julie Rowland, University of Auckland
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.