What is a rift valley ? How did it come to be?

Rift. Rift.

rift valley

The surface depression structure of the earth's deep formation, which is bounded by high-angle faults and is a long strip of crustal descent zone, is a large geological tectonic unit hundreds to thousands of kilometers long. The Englishman Gregory first proposed it in 1894. Rift is a tectonic type in the initial stage from continental collapse to ocean opening during plate tectonic movement, and it is also a tectonic type of lithospheric plate growth boundary, which is developed on the mid-ocean ridge in the continental crust region.

At present, the largest rift valley is developed on the mid-ocean ridge of the major ocean basins, and the rift morphology is maintained well and the characteristics are obvious. In general, the valley is 25 30 km wide, 2 3 km above the deepest ocean floor, and the difference in elevation from the nearby ocean floor is one km. The total length of the global mid-ocean ridge rift is more than 60,000 kilometers.

Although the mid-ocean ridge rift zone is often truncated and staggered by conversion faults, it is still clearly coherent. Continental rifts can be divided into two types: active rift and passive rift according to the different formation methods. Active rift is the long-term action of the rising heat convection of the earth's mantle, which causes the continental lithosphere to thin and uplift and rupture, and then it collapses to form rift valleys, such as the East African rift valley and the Gulf of Aden in the Red Sea.

Passive rifting is the formation of rift due to the thinning and rupture of the lithosphere due to the extension or shearing of the earth's crust.

More than 10 million years ago, the fracture of the Earth's crust formed this huge subsidence zone. According to the theory of plate tectonics, this is where the land masses separated, i.e., eastern Africa is located in a zone where the upward flow of mantle material is strong. Under the action of upwelling, the crust of East Africa is uplifted to form a plateau, and the dispersion of the upwelling in opposite directions on both sides causes the fragile part of the earth's crust to open up and subside, and become a rift zone.

The average rate of tensioning is 2 cm 4 cm per year, and this action has continued to this day, and the rift zone continues to expand to both sides. Because this is a zone of active crustal movement, there are many volcanoes**.

The Great Rift Valley is a geographical wonder that runs through East Africa, the world's largest fault collapse zone, known as the scar of the earth, and is said to have been formed by the fracture of the strata in eastern Africa due to the movement of the earth's crustal plates about 30 million years ago. Geographers predict that in the future, the African continent will break along the rift valley into two continental plates.

According to the research of geologists, about 30 million years ago, due to the strong crustal fracture movement, the same as the Arabian.

Continental drift of paleocontinental facies separation.

movement to form this rift. At that time, the crust in this area was in a period of great movement, and the whole area was uplifted, and the mantle beneath the crust.

The matter ascends and shunts, creating a tremendous tension. It is precisely under the action of this tension that the ridge of matter causes a large fracture in the earth's crust, thus forming a rift.

Due to the continuous uplift, the fractures of the earth's crust continue to occur, and the underground lava town rock continues to gush out, gradually forming a tall lava plateau. The volcanoes on the plateau become numerous peaks, and the subsidence of the fault becomes the valley floor of the Great Rift Valley.