Wednesday, November 11, 2009

The Creation of a New Sea

Photo courtesy: © thebigmonkey via flickr.

None of us alive today will live to see the end of this event; but, we are witnessing a miracle of nature - a new sea is forming in the Ethiopian desert. In 2005, in Afar, Ethiopia, a 35-mile long volcanic rift opened in the desert. There was speculation at the time that this might be the beginning of a new ocean; but, the scientific community as a whole felt this was not the case; and, all but, dismissed the idea. It has since been determined that this is indeed the beginning of a new ocean as detailed in the paper written by an international team of scientists which has been published in the Geophysical Research Letters journal.

The rift began opening when Mount Dabbahu erupted for the first time in recorded history. The rift took just three weeks to spread up to 25’ wide in places along a fault line in the Afar desert. This massive chasm is threatening to tear the continent of Africa into two pieces. With the rift heading in the direction of the Red Sea, Erithea, Djibouti and part of Ethiopia could eventually split off 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 as traditional wisdom would indicate, magma was pushed up in the middle of the rift and the whole thing began "unzipping" in either direction. This 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.

On a more human level, this means that populations that live in areas near the rift are in greater danger than previously thought. More damage is done by one major eruption than several more minor ones.

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

The report went on to say that the rift is developing in a way that is "nearly identical to those at the bottom of the world's oceans".

"This work is a breakthrough in our understanding of continental rifting leading to the creation of new ocean basins," says Ken Macdonald, professor emeritus in the Department of Earth Science at the University of California, Santa Barbara. It should be noted that Professor Macdonald is not affiliated with the research.

"For the first time they demonstrate that activity on one rift segment can trigger a major episode of magma injection and associated deformation on a neighboring segment. Careful study of the 2005 mega-dike intrusion and its aftermath will continue to provide extraordinary opportunities for learning about continental rifts and mid-ocean ridges," Macdonald continues.

"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 investigation was led by Atalay Ayele, a professor at the Addis Ababa University in Ethiopia. He and his colleagues painstakingly gathered seismic data surrounding the 2005 volcanic eruption that opened the rift to more than 20’ in just a matter of days.

Ayele combined his data from Ethiopia with data from Eritrea collected with the help of Ghebrebrhan Ogubazghi, a professor at the Eritrea Institute of Technology; and, data from Yemen collected with the help of Jamal Sholan of the National Yemen Seismological Observatory Center.

Ayele's reconstruction of events showed that the rift did not open in a series of small earthquakes over an extended period of time as previously thought; but, tore open along its entire 35-mile length in just days.

"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 Ebinger.

Ebinger points out that the areas where the seafloor is spreading are almost always situated under miles of ocean. This makes it nearly impossible to monitor more than a small section of ridge at any one time; so, there is no way for geologists to quantify 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."

Cindy Ebinger and her team will continue to monitor the rift.

The rift from different angles:

The rift in Afar, Ethiopia (credit University of Rochester).

The rift in Afar, Ethiopia (credit University of Rochester).

Via TreeHugger, University of Rochester News,

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