19 May 2007 04:14

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  • Title: [SW Country](AFP) Africa gives birth to new ocean : study
  • From:[]
  • Date :[Fri, 10 Mar 2000 08:02:43 ]

Friday, March 10 1:35 PM SGT
Africa gives birth to new ocean: study
ASMARA, March 10 (AFP) -
The Arabian geological plate, the land mass that is now Saudi Arabia and
Yemen, is struggling to break free and drift north of the fixed Nubia and
Somalia plates, which also hold Ethiopia, Eritrea and Djibouti, scientists
say.
The tectonics battle has raged for 30 million years, according to Isabelle
Manighetti, a researcher in active tectonics at the Paris-based Institute de
Physique de Globe.
"There is no equivalent anywhere else on earth," said Manighetti, the
institute's co-coordinator of the Horn of Africa study project.
"We are seeing a continent give birth to an ocean, the youngest ocean on
earth," said Manighetti.
The three-member research team was in Eritrea last month to arrange
scientific cooperation with Asmara University for the research project,
which has so far lasted nearly a decade and has involved several
universities in France.
"The region makes for a very unique laboratory. Here we can understand the
basic mechanism of the creation of an oceanic floor, and we can do detailed
studies because everything is visable," she said, noting that the process
seen today is the same geological process that created the North Atlantic
Ocean more than 80 million years ago.
Showing a map of the region, Manighetti points out how perfectly the corner
of Arabia fits into the Horn of Africa's Afar region near Djibouti.
"When the two plates broke apart, they created the Afar triangle," explained
Manighetti, pointing to the bottom of the "V" shape where the Red Sea and
Gulf of Aden meet.
That break opened up two new oceanic basins, but Manighetti notes the
unusual break is not yet complete.
"For some reason there was no break at the corner, so the plates remain
attached at Yemen, Djibouti and Eritrea," she said.
"Our project is to understand how that break will happen," she said.
The current hypothesis is an enormous hot spot coming from deep in the earth
which began erupting 30-million years ago, and continued over the relatively
short geological time of one-million years.
"It was a catastrophic event, probably changing the climate of the earth and
causing several species to become extinct," explained fellow project
coordinator, Michel Cara, a geological physics professor at Strasbourg
University.
The evidence today is a lava field stretching 1,000 kilometers (600 miles)
across, and two to three kilometers deep, with several small hot spots
remaining throughout in the region.
Scientists believe the force of the eruptions caused Arabia to begin
breaking away, thereby creating two large fissures which became the Red Sea
and Gulf of Aden, but it is in the Afar region, the epicentre of the hot
spot, where the composition is too soft to make a clean break, thereby
preventing the two fissures from meeting.
"They are about 100 kilometers apart, but all fissures in the region between
them go parallel instead of perpendicular, which would connect them," said
Manighetti, noting that the field of fissures and faults is about 10
kilometers wide and 40 kilometers long.
The research team believes that over the next four million years the zone
will become weakened and part of the Afar region, probably the section in
Eritrea, will break away with Arabia.
"There is a constant struggle for the plates to fully break apart, with
movement measured at the very fast geological rate of two centimeters per
year," said Manighetti.
The result is a major earth quake zone stretching underneath the Red Sea and
Aden Sea, and down the Rift Valley through Eritrea, Djibouti and Ethiopia.
A map of previous earth quakes in the region shows the vulnerability of the
Horn.
"Asmara could be destroyed by an earthquake," said Cara. "The seismic risk
is significant."
Part of the project is to install seismometers, a high-tech mapping devise
that can also help scientists to understand the earth's deep structures, and
hopefully in the future predict earthquakes.
"The area is really very poorly covered," explained Cara, noting that in
California there are thousands of seismometers, but from Saudi Arabia to the
Seychelles Islands four thousand kilometers away, there are only five.          


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