Friday, December 09, 2005

Scientists: Fissure Could Be a New Ocean

Image: Dabbahu
A 1999 satellite image shows the area around Ethiopia's Dabbahu volcano, also known as Boina. Researchers say a fissure is opening up in the desert near the volcano, and eventually may become a new ocean basin. (MSNBC)

Yahoo! News via AP -- Ethiopian, American and European researchers have observed a fissure in a desert in the remote northeast that could be the "birth of a new ocean basin," scientists said Friday.

Researchers from Britain, France, Italy and the U.S. have been observing the 37-mile long fissure since it split open in September in the Afar desert and estimate it will take a million years to fully form into an ocean, said Dereje Ayalew, who leads the team of 18 scientists studying the phenomenon.

The fissure, now 13 feet wide, formed in just three weeks after a Sept. 14 earthquake in a barren region called Boina, some 621 miles north east of the capital, Addis Ababa, said Dereje.

"We believe we have seen the birth of a new ocean basin," said Dereje of Addis Ababa University. "This is unprecedented in scientific history because we usually see the split after it has happened. But here we are watching the phenomenon."

The findings have been presented at a weeklong American Geophysical Union meeting taking place in San Francisco that ends Friday.

"It's amazing," the BBC quoted one of the Afar researchers, Cindy Ebinger of the Royal Holloway University of London, as saying in San Francisco. "It's the first large event we've seen like this in a rift zone since the advent of some of the space-based techniques we're now using, and which give us a resolution and a detail to see what's really going on and how the earth processes work."

The Ethiopian Afar Geophysical Lithospheric Experiment,
involving scientists from Royal Holloway and the universities of Leicester, Leeds and Addis Ababa, is using sensitive instruments to study what is happening deep within the earth.

Dereje said that the split is the beginning of a long process, which will eventually lead to Ethiopia's eastern part tearing off from the rest of Africa, a sea forming in the gap. The Afar desert is being torn off the continent by about 0.8 inches each year.

"The crust under Afar is becoming like the crust found in the Red Sea," said Dereje, head of earth science at Addis Ababa University. "Once the crust is formed you will have water because it is a low area and the water will migrate from the Red Sea and the Gulf of Aden. It becomes a basin."

The scientists plan to set up an observatory to watch the split and see how it develops.



Why should we study the Rift?
Our aim is to understand one of the fundamental processes occurring on our Earth, namely the break-up of continents. But there are also immediate economic, environmental and cultural objectives. We hope to identify possible geothermal fields in the Rift. Oil and geothermal exploration geologists also need to know about the embryonic stages of continental break-up to work out how to discover and exploit reserves along other continental margins where plates have successfully rifted, e.g. the oilfields offshore west Africa. The Rift is environmentally hazardous and our studies will help in both earthquake and volcanic risk assessment. The region of Afar is an area closely linked to the development of Man. Anthropologists, archaeologists and geographers, in their studies of early Man and his interaction with the environment, need to know about the active processes of rifting; the type of faulting; the amount and timing of crustal subsidence and uplift; the distribution of volcanic centres and their associated volcanic rocks.

EAGLE is an international project. It has involved over 80 scientists in a series of seismic projects in the Ethiopian Rift Valley and the south-western corner of Afar over a period of two years. Two large deployments of seismic recording instruments took place between October 2001 and January 2003. In the first deployment 80 instruments including seismometers, data loggers, batteries, solar panels and GPS receivers have been distributed over a 250x250km2 area covering the rift and centred on the Nazret ‘volcanic segment’ to the south-east of Addis Abeba. This segment lies within a new zone of active crustal deformation marked by aligned chains of volcanoes, vents, faults and a 60km long ‘dyke’ zone comprising vertical intrusions of magma from deep magma reservoirs. The instruments recorded seismic waves from global and local earthquakes. The collected data is now being worked on in laboratories in Ethiopia, the US and the UK. The seismic waves travelled up beneath the rift and are now providing an image of the Earth’s crust and mantle to depths of a few hundred kilometres, illuminating the hot mantle zone and pockets of molten rock that are believed to underlie this region. The local earthquakes are providing direct evidence of active faulting and deformation within the rift. In January 2003, some 80 scientists were involved in the second major experiment, deploying a further 1000 seismic instruments on two 400km long profiles, the first from the Blue Nile in the Ethiopian Highlands to the north of Addis Ababa, across the Rift and the Nazret volcanic segment, and up and over the south-eastern flank of the Rift. The second profile was along the Rift Valley from Awasa in the south through Nazret to Gewane in the north. The project required the use of 40 4x4 all-terrain vehicles, drilling rigs, equipment trucks, infield communication systems and other supply systems. A total of 20 shotpoints at which a total of 22 tonnes of explosive was detonated at the bottom of deep boreholes and in two lakes, provided seismic energy which is now producing a very high resolution image of the crust and upper mantle to depths of about 50km.Early results from the whole project show data of excellent quality with important implications for both the rupture of continents, as well as volcanic and seismic hazards and hydrothermal exploration in Ethiopia. Some of the results are currently under review by peers, and these results will be posted when the review process is complete. One conclusion can be drawn, even at this early stage: large amounts of volcanic material have been intruded into the crust beneath the rift, particularly in the central rift near the lines of active and dormant volcanoes. Future work involves evaluation of the local seismicity and its relation to magmatism, as well as modelling of the geological processes that have led to the formation of the Ethiopian rift and its transition northwards into Afar.
In Closing –

The project has been one of the largest seismic projects ever undertaken by a group of UK – US universities. It has generated important links with colleagues from the University of Addis Ababa and the Ethiopian Geological Survey. It has involved young Ethiopian, US and UK scientists at the outset of their careers and forging immensely strong links between the international colleagues. The results will be of importance to all Earth Scientists and as well as being published in the international scientific journals and popular literature, will be presented at a major international Earth Science meeting on ‘The East African Rift System: Development, Evolution and Resources’ to be held in Addis Ababa in June 2004.

It has been a project for the beginning of the 21st Millenium.


According to the website, one of the objectives of the US-Africa Workshop on Anatomy of Continental Rifts was:
- To fully involve USA partners in the assessment and evaluation of East African Rift System resource potential (oil, coal and gold deposits, geothermal energy, groundwater, agricultural and construction materials) that is necessary for African development.

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