AFRICA'S NEW OCEAN A Continent Splits Apart

[Cricket]

AFRICA'S NEW OCEAN
A Continent Splits Apart
By Axel Bojanowski

Normally new rivers, seas and mountains are born in slow motion. The
Afar
Triangle near the Horn of Africa is another story. A new ocean is
forming there
with staggering speed -- at least by geological standards. Africa will
eventually lose its horn.

Geologist Dereje Ayalew and his colleagues from Addis Ababa University
were
amazed -- and frightened. They had only just stepped out of their
helicopter
onto the desert plains of central Ethiopia when the ground began to
shake under
their feet. The pilot shouted for the scientists to get back to the
helicopter.
And then it happened: the Earth split open. Crevices began racing
toward the
researchers like a zipper opening up. After a few seconds, the ground
stopped
moving, and after they had recovered from their shock, Ayalew and his
colleagues
realized they had just witnessed history. For the first time ever,
human beings
were able to witness the first stages in the birth of an ocean.


Normally changes to our geological environment take place almost
imperceptibly.
A life time is too short to see rivers changing course, mountains
rising
skywards or valleys opening up. In north-eastern Africa's Afar
Triangle, though,
recent months have seen hundreds of crevices splitting the desert
floor and the
ground has slumped by as much as 100 meters (328 feet). At the same
time,
scientists have observed magma rising from deep below as it begins to
form what
will eventually become a basalt ocean floor. Geologically speaking, it
won't be
long until the Red Sea floods the region. The ocean that will then be
born will
split Africa apart.

The Afar Triangle, which cuts across Ethiopia, Eritrea and Djibouti,
is the
largest construction site on the planet. Three tectonic plates meet
there with
the African and Arabian plates drifting apart along two separate fault
lines by
one centimeter a year. A team of scientists working with Christophe
Vigny of the
Paris Laboratory of Geology reported on the phenomenon in a 2006 issue
of the
Journal of Geophysical Research. While the two plates move apart, the
ground
sinks to make room for the Red Sea and the Gulf of Aden.

Bubbling magma and the smell of sulphur

A third crevice cuts south, splitting not far from Lake Victoria. One
branch of
the rift runs to the east, the other to the west of the lake. The two
branches
of this third crevice are moving apart by about one millimeter a year.


The dramatic event that Ayalew and his colleagues witnessed in the
Afar Desert
on Sept. 26, 2005 was the first visual proof of this process -- and it
was
followed by a week-long series of earthquakes. During the months that
followed,
hundreds of further crevices opened up in the ground, spreading across
an area
of 345 square miles. "The earth has not stopped moving since,"
geophysicist Tim
Wright of the University of Oxford says. The ground is still splitting
open and
sinking, he says; small earthquakes are constantly shaking the region.

Scientists have made repeated trips to the area since the drama of
last
September. Locals have reported a number of new cracks opening in the
ground,
says geologist Cynthia Ebinger from the University of London, and
during each
visit, new crevices are discovered. Fumes as hot as 400 degrees
Celsius (752
degrees Fahrenheit) shoot up from some of them; the sound of bubbling
magma and
the smell of sulphur rise from others. The larger crevices are dozens
of meters
deep and several hundred meters long. Traces of recent volcanic
eruptions are
also visible.

In a number of places, cracks have opened up beneath the thin layer of
volcanic
ash that covers the region. As there is no ash in the fissures, it's
clear that
they opened up after the volcanic eruptions, most of which took place
at the end
of September or in October, 2005. A number of locals who fled the
eruptions have
reported that a black cloud of ash -- spewed out of the Dabbahu
volcano --
darkened the sky for three days.

A new ocean floor on the Earth's surface

Basalt magma has risen into some of the crevices. For the moment,
Ayalew
explains, the lava seems not to be rising further. A number of recent
eruptions,
though, have left layers of new basalt lava on the Earth's surface.
And it's the
exact same kind of lava that spews out of volcanic ridges deep under
the ocean
-- a process which slowly pushes older lava sediments away on either
side. The
process has only just begun in the Afar Triangle -- and scientists for
the first
time can witness the birth of a new ocean floor.


The source of the African magma looks to be a gigantic stream of
molten rock
rising from beneath the Earth's crust and slicing through the African
continental plate like a blow torch. It's a process that began thirty
million
years ago when lava broke through the continent for the first time,
separating
the Arabian Peninsula from Africa and creating the Red Sea.

Now, it's the Afar Triangle's turn and it's sinking rapidly. Large
areas are
already more than 100 meters (328 feet) below sea level. For now, the
highlands
surrounding the Denakil Depression prevent the Red Sea from flooding
these
areas, but erosion and tectonic plate movement are continually
reducing the
height of this natural barrier. The Denakil Depression, which lies to
the east
of Afar, is already prey to regular floods -- each flood leaving
behind a crust
of salt.

Africa to lose its horn

The chain of volcanoes that runs along the roughly 6,000 kilometer
(3,730 mile)
long East African Rift System offers further testimony to the breaking
apart of
the continent. In some areas around the outer edges of the Rift
System, the
Earth's crust has already cracked open, making room for the magma
below. From
the Red Sea to Mozambique in the south, dozens of volcanoes have
formed, the
best known being Mt. Kilimanjaro and Mt. Nyiragongo.

These fiery mountains too will one day sink into the sea.
Geophysicists have
calculated that in 10 million years the East African Rift System will
be as
large as the Red Sea. When that happens, Africa will lose its horn.