The East African Rift or EET is an old, active continental rift system off the east coast of Africa. It shares its border with the Indian Ocean and the Arabian Sea. The EAR started developing around the start of the Miocene, twenty million years ago. In the last century it has been recognized as a separate and unique section of the larger Rift Valley. Geologists call it the East African Rift Valley (EARV) because it lacks the chain of permanently south-westerly trending crevices that divide the rest of the Rift valley into the southernmost sections.
Major geological feature of the EET
The major geological feature of the EET is the massive ‘plateaus’ or ridges and depressions on the flat geological surface of the southern margin of the rift valley. These ridges are not steep but have sharp grade-bars and sharp ridges. Geologists and geophysicists refer to these features as ‘globes’. One of the major rift valley tectonic events is the collision and explosion of the super volcanoes. This process left the landmasses which now form the African continent with parallel slope topography. The formation of plateaus on the East African rift valley has made it an archaeological region as many artifacts, including Preolithic art, have been discovered in the area.
Another division of the Earth’s crust is evident in the formation of mountain ranges. There are several examples in east Africa where mountains were formed by the movement of plateaus across the surface of the earth. These mountains range from the Green belt to the most rugged region known as the Black Belt. The formation of mountains can be traced back to the great explosion of super volcanoes. The rift valley was also a major part of this volcanic activity.
Another division of the Earth’s crust can be found in the movement of tectonic plates across the African rift valley. This movement of plates is evident in the outlines of the continents as they overlap one another. The outlines of North America, South America, Africa, Australia and Asia can be seen to have overlapped by these plateaus. The formation of the Indian and American continent is evident by the Himalayas. Similarly, the formation of the Australian and Indian plates is found along the edges of the rift valleys which are still parallel to each other.
Major rift valley earthquakes
One of the major rift valley earthquakes is the Ashau Valley earthquake which was a 6.2 magnitude earthquake. This earthquake also marked the beginning of the new super volcano operation which is what we know now as the Volcanoes National Park. In this event, there was a major eruption which released lava and spewed rocks high into the air. It is not uncommon for the crust of the earth to move or reverse movement due to pressure or an over pressurization caused by tectonic plates.
Movement of the lithosphere
The movement of the lithosphere is also a key player in the dynamics of the Earth. On the timescales that these shifts take place, it is possible to see major changes in the climate. Some scientists believe that the African rift valley has been affected by new ocean rifts which have formed due to plate movements. They also believe that there may be links between the Amazon and the East African Rift Valley, which may have resulted in the massive flood which ultimately buried the dinosaurs.
How did the massive volcanic eruptions occur ?
There are several theories on how the massive volcanic eruptions occurred. The most accepted theory is that the explosion came from the magma. This theory can be applied even in non-volcanic events where tectonic plate movement caused the movement of the landmasses. If you go even further back in time, you will find that the entire Rift Valley was formed through a massive bombardment of space debris. When the space debris impacted the Earth, the vaporized material became molten and re-formed into the mountains that we now know as the Himalayas and Indus valleys.
Even when the erupting volcano sends lava tumbling to the surface, it does not usually impact the surface in a significant way. Lava flows tend to pool near the volcano perimeter and this mass of melted rock acts as an insulator which keeps the warm air around the volcano constant. This cooling effect causes the lava to stay solid on the edges of the crater and it rarely flows out into the nearby surrounding areas. In this way, the volcano remains fairly cool and does not suffer significant temperature fluctuations that could affect the climate in the area. Changes in the weather can sometimes affect rifting in the EET, but the evidence is too thin to make a valid prediction.