Normally, geological changes to our environment are gradual, subtle and perhaps take place over lifetimes. In the Afar Triangle, in northeastern Africa, however, recent months have seen hundreds of crevices split the desert floor, and the ground has slumped by as much as 100 meters (328 feet) Meanwhile, magma has risen from deep below the surface as it begins to form what will eventually become a basalt ocean floor.

In time, the Horn of Africa will separate from the continent and there will be a large body of water between the two land masses, a body of water about the size of the Red Sea.

Geologist Dereje Ayalew and his colleagues from Addis Ababa University witnessed the first visual proof of the ocean-birth process, in the Afar Desert in mid-September last year. Three tectonic plates meet in the Afar Triangle, which cuts between Ethiopia, Eritrea and Djibouti, with the African and Arabian plates drifting apart along two separate fault lines by one centimeter per year. While the two plates move apart, the ground sinks to make room for the Red Sea and the Gulf of Aden. A third crevice cuts south; one branch of the rift runs to the east, the other to the west of Lake Victoria. The two branches of this third crevice are moving apart by about one millimeter a year.

In the far-distant past, oceans such as the Atlantic have formed when supercontinents have torn apart. Indeed, North America and Europe are still moving in opposite directions at about the pace fingernails grow. Researchers have long recognized that the Afar region, an inhospitable depression in northeastern Ethiopia, has been contorted by similar forces in recent geological time. Although the idea of Africa splitting is not new, the event in September is said to be unprecedented in scientific history: it was witnessed.

Week-long series of earthquakes struck following Ayalew and his colleagues' dramatic experience. During the following months, hundreds more crevices opened up in the ground, spreading across an area of 345 square miles. Scientists repeatedly have been back to study the area, and new crevices are discovered each time. Locals also have reported a number of new cracks opening in the ground. From some of the cracks shoot fumes as hot as 400 degrees Celsius (752 degrees Fahrenheit). As well, "the sound of bubbling magma and the smell of sulphur rise from others," reports SPIEGEL online.

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. Many 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.

Image: C.Ebinger - BBC

Particularly of note, though, is that basalt magma has risen into some crevices, and recent eruptions have left layers of new basalt lava on the earth's surface. And, according to SPIEGEL, "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.

While the process has only just begun in the Afar Triangle, scientists — nay, humans — for the first time can witness the birth of a new ocean floor.

Thirty-million years ago, lava broke through the continent for the first time, separating the Arabian Peninsula from Africa and creating the Red Sea. That process provides the source of the present African magma, which seems to be a gigantic stream of molten rock rising from beneath the earth's crust and slicing through the African continental plate "like a blowtorch." The magma, which is identical to lava that spews out of deep oceanic volcanic ridges, is what will form the new ocean floor in time.

Now the Afar Triangle is sinking rapidly. Large areas already are 328 ft. below sea level. SIEGEL notes, "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."

Geophysicists calculate that even the dozens of volcanoes between the Red Sea and Mozambique, including perhaps the best-known — Mt. Kilimanjaro — one day will sink into the sea, and that in 10 million years the East African Rift System will be as big as the Red Sea…at which point Africa will lose its horn.

Resources

Africa's New Ocean: A Continent Splits Apart
by Axel Bojanowski
SPIEGEL, March 15, 2006

Geologists Witness 'Ocean Birth'
by Roland Pease
BBC News, Dec. 8, 2005

Volcanoes threaten to divide Africa
BBC News, Feb. 18, 2002