News Update: New African Ocean Emerged with Spectacular Speed


In 2005 an Ethiopian volcano erupted, tearing a thirty-five mile rift in the country in a matter of days -incredibly fast in geological terms – especially since this may well be the first sign of an incoming Ethiopian Ocean.  Nature seems to like keeping us on our toes. 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.

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.

It's known that new oceans form as magma forces its way into rifts between tectonic plates, but since every other such system worked – and is now under miles of ocean – we can't actually get down there for a detailed look.  Instead, an international collaboration of scientists both local and abroad studied the sudden "mega-dike intrusion" (a much less scary way of saying "holy hell our country just ripped open") and found that it matches all the signs for a prototype ocean bed.

"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.

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

The spectacular speed is what stunned scientists: it was assumed that such events occurred slowly in smaller steps, not sudden tectonic upheavals of the kind that cut the Earth itself open in less than a week.  We were wrong about that.  This raises important questions, both in terms of geophysical processes which shape the Earth we live on, and for anyone living within an earthquake of such a region.

Even with earthquake acceleration it'll be a long time before an Ethiopian port becomes an issue.  But this sudden starting point will be an international hub of oceanographic interest until then – and with oceanographers carefully studying the African desert, it's proof that Nature has a sense of irony.


The Daily Galaxy via University of Rochester


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