African desert rift confirmed as new ocean in the making

Nov 02, 2009

(PhysOrg.com) -- In 2005, a gigantic, 35-mile-long rift broke open the desert ground in Ethiopia. At the time, some 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 the beginning of a new sea.

The new study, published in the latest issue of , 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 of earth and environmental sciences at the University of Rochester and co-author of the study.

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"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, and who 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."

"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."

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 20 feet in width in just days. Along with the seismic information from Ethiopia, Ayele combined data from neighboring 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 Center. The map he drew of when and where earthquakes happened in the region fit tremendously well with the more detailed analyses Ebinger has conducted in more recent years.

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 35-mile 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 Ebinger.

Since the 2005 event, 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 Ebinger. She explains that since the areas where the seafloor is spreading are almost always situated under miles of , it's nearly impossible to monitor more than a small section of the ridge at once so there's 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."

Ebinger and her 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.

Source: University of Rochester (news : web)

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bhiestand
5 / 5 (8) Nov 02, 2009
Had to do a little searching for pictures since the article didn't include any... I believe http://www.bgs.ac...arge.jpg is the right spot.
John_balls
Nov 02, 2009
This comment has been removed by a moderator.
pres68y
1.5 / 5 (2) Nov 03, 2009
Yes, thank you for the picture.

Looks like a mini Grand Canyon formed in just days?
(millions of years reduced to millions of seconds!)
LKD
not rated yet Nov 03, 2009
Thank you, bhiestand. I really needed that link as I couldn't tell what they were trying to show on Google maps.

Very interesting. Will the gap actually tear a line through Djibouti and then spread out a great distance like the Red?
bhiestand
not rated yet Nov 03, 2009
My pleasure, LKD. Pictures were definitely needed on this one.

Yeah, pres68y, it's wonderful to be able to witness the quick ones. I think there's something fundamentally awe-inspiring about rapid geologic changes on these scales. In the last few decades we've learned that rapid/sudden change really does happen. My bet is that we'll discover it happens more often than we think.

I honestly don't know how it will continue. http://pubs.usgs....ica.html shows a pretty good map of it. I've heard that East Africa could end up an island of its own, but I imagine that would involve multiple new rifts and quite a lot of time.

In the mean time, they're investing in geothermal energy plants :) (not on the rift itself, of course)
LKD
not rated yet Nov 03, 2009
Very useful link once more. Thank you. I wonder? Which will go first? East Africa, or LA sinking into the ocean? :)

Absolutely amazing forces at work here. It is such a shame that this kind of information is not taught in schools, but comes after you no longer have the time to really appreciate the effects.
bhiestand
not rated yet Nov 03, 2009
Great timing to ask that question, LKD. Just saw this one today: http://www.physor...243.html

"The ocean's formation is happening slowly, likely to take a few million years. It will stretch from the Afar depression (straddling Ethiopia, Eritrea and Djibouti) down to Mozambique," he said.


I suppose our (California's) fate depends on how long it takes Texas to develop the technology to speed the process :)

The biggest shame is that our brightest minds are working on everything but educating children, meanwhile our children are being taught that education is overrated and you only go to college because it's a job requirement. All this at a time when information is more readily available than food!
LKD
not rated yet Nov 04, 2009
"I suppose our (California's) fate depends on how long it takes Texas to develop the technology to speed the process :)"

Oh, that's hilarious. I haven't laughed this hard all week!

The link is good, but really should have been part of the original article. I wonder why the writers felt that this needed to be revisited to explain all of 1 more point?

As for education, that about sums up most people's view on college and the whole process. It's a shame, but what can you do when the first 20 years of your life are spent desperately trying to grow up as fast as possible, then spending the rest of your life trying to fight it?
fixer
not rated yet Nov 07, 2009
Is this rift below sea level? and if so will the volume be enough to cause a drop in sea level.