The media around the world reported a few days ago the appearance of a large crack in the surface near Mai Mahiu, a southern Kenyan city located in the Great Rift Valley, the geological fracture of almost 5,000 kilometers of length that crosses the east of the African continent from north to south, between Eritrea and Mozambique.
The fissure is more than a kilometer long, up to 50 meters deep and about 10 meters wide (photo), and many take it as proof that Africa is splitting in two. They are right?
An old separation
In reality, Africa has been splitting for at least 20 million years. The region delimited by the Rift separates from the rest of the continent at a rate of 6 or 7 millimeters per year, but let no one be alarmed: the rupture will not be complete for 10 million years. When finished, it will create a large island seven times the size of Madagascar.
Plate tectonics is the geological theory that explains this phenomenon: a series of rigid plates covers the Earth, and they have not stopped moving for hundreds of millions of years. Wherever they touch, the seismic and volcanic activity is greater. The currents caused by radioactivity of isotopes present in the planet’s mantle and core are transmitted to the surface by the mantle, and the consequent differences in temperature create convection currents that move oceans and continents at an imperceptible rate on a human scale.
The huge Rift Valley marks the division between the African plate, the Somali plate, the Indian plate, and the Arabian plate. In that place, part of the earth’s crust separates and the bottom is filled with volcanic rocks, because the earth’s mantle is rising, which results in constant eruptions and earthquakes of varying intensity. Geologists predict that the land will sink along the Rift, which will be flooded by water. This great geological move will end the partition of Africa in two.
Does this have something to do with the rift in Kenya? It seems not. According to the scientists, the most likely explanation is that the intense rains that have fallen in the area in recent weeks have eroded the terrain to cause the spectacular fracture. Seismic activity is not responsible, although it is frequent there, as it happens throughout the Rift Valley, for the reasons explained.
Continents always adrift
The phenomenon of continental drift had been suspected since the 18th century, when it was realized that the shapes of some continents fit together like the pieces of a puzzle. The most obvious example is obvious when looking at the outline of West Africa and South America on a map. Had they been together? Yes, and the proof lies under the sea. The Atlantic Ridge, the underwater volcanic ridge that divides the Atlantic Ocean from North to South, is like a seam that attests to the existence of plate tectonics.
190 million years ago, Africa and South America were united by what is now the Atlantic Ridge, but the geological waltz separated them, and has continued to do so for at least 150 million years, at a rate of a few centimeters per year . About 240 million years ago, the continents formed a large structure called Pangea, something that has been known thanks to fossils and the silhouette of today’s continents.
