In eastern Africa, tectonic plates are not behaving quite the way geologists expect them to. Not far from the capital of Kenya, Nairobi, a giant crack formed after heavy rains back in 2018: up to 20 meters wide, up to 15 meters deep, and stretched for several kilometers, including across the highway.
Geologists then immediately explained that this is only a small manifestation of a mega-process that has been going on for millions of years not only in Kenya, but also in Ethiopia, Tanzania and Mozambique.
This process consists in the gradual separation of lithospheric plates. Volcanoes have formed in places on the border between them and in general there is strong geological activity: the so-called East African Fault passes there.
That part of Africa, which is to the right of the fault, belongs to the so-called Somali plate, that to the left is the Nubian plate. The Arabian Peninsula is already the Arabian Plate. So, according to the forecasts of scientists, everything goes to the fact that the movement of the Somali plate will tear off the east of Africa from the rest of the continent, and this separated part of it will become an island for a while, and then hit the Arabian plate.
From this collision in the south of Yemen, apparently, mountains are formed. This will happen, according to rough estimates, in a few million years.
Geologists have compared this very gradual separation of the plates with the kids gooey “slime” toy, a sticky viscous mass: if you hit it with a hammer, it will immediately burst, but if you gradually stretch it, then it becomes thinner, without breaking. This is approximately what happens to the earth’s crust along the East African Rift, the researchers explain.
But the fact is that they have long been alarmed in this process by one interesting thing. Logically and from observations of similar faults on the planet, geologists expect that the two plates should diverge in opposite directions, that is, move, as it were, perpendicular to the fault, to the left and right of it.
And so it really happens but in addition, these plates also “walk” along the fault, that is, parallel to it. This confirms the comparison of data from 30 satellites and scientists cannot understand this displacement along the fault.
There are two phenomena that are suspected of this longitudinal, parallel “walking”. One phenomenon is the so-called lithosphere buoyancy. This is such a property of the earth’s crust, thanks to which it is held on top and does not sink in the mantle – just like icebergs do not sink in water. This happens for exactly the same reason that icebergs “float”: the density of ice is less than that of water. Accordingly, the density of the solid crust is less than that of the viscous mantle. That is, both that and the other, as it were, pushes outward and there is a version that the mysterious parallel movement of the plates is caused by some manifestations of this buoyancy, this expulsion.
The second suspected phenomenon is a truly curious phenomenon that seismologists discovered: they “listened” to how earthquake shock waves pass through the bowels of the Earth, and realized that there are two mysterious gigantic structures inside our planet that are slightly denser than the rest of the surrounding mantle. That is, it is some slightly different material, it is different.
One such “alien” piece is located under the Pacific Ocean, and the second is just under Africa. By the way, there is even such a hypothesis that these are parts of another planet that collided with the Earth billions of years ago, in the “childhood” of the solar system.
These structures are called superplumes and s geologists have established, flows of mantle mass spread from them in the upper part of the mantle under the lithosphere, and they move the plates above them.
To resolve the dispute, they made a three-dimensional modeling of the geological process taking place in East Africa and it turned out that the superplume is to blame: it causes the mantle to move from the southwest to the northeast of the continent, that is, in fact, along the fault.
But again, it is worth emphasizing that this huge mass of mysterious substance under Africa causes precisely the longitudinal displacement of the plates, and the fault itself as a whole is the result of the totality of everything that happens in the bowels of our planet.