Geological events in Ethiopia

What do you know about geological events in Ethiopia? What happened during the cenozoic era in Ethiopia?

The whole of Africa essentially consists of a basement of ancient crystalline rock. During the Precambrian era, Ethiopia was made up of huge mountains which were folded and faulted. During the Paleozoic era, the land was greatly affected by persistent denudation (erosion) and peneplanation. In many parts of Ethiopia, there was no significant rock formation in this era.

At the beginning of the Mesozoic era, the land surface sank, very slowly. As a result, the sea invaded the land from the southeast towards the northwest. In this process, layers of sandstone and limestone were deposited, one over the other. The layers of sandstone, referred to as Adigrat sandstone, were formed first, followed by deposition of layers of limestone called Hintalo limestone. Gradually, the landmass which was under the sea started uplifting, and the land emerged out of the sea toward the end of Mesozoic era. Following this, the sea started to retreat in the southeast direction, and it deposited other layers of sandstone called Upper sandstone. Hence, by the end of the Mesozoic era, many parts of Ethiopia were covered by the three layers of Mesozoic marine sediment.

During the Cenozoic era, Ethiopia experienced two major geological events:

I - The uplift of the Ethiopian landmass, followed by crustal deformations and the emission of an immense lava flow, Trapean (old) lava series, to the surface. This process produced the Ethiopian highlands.

II - During the middle tertiary, the land was subjected to major vertical displacements, which produced the formation of the Ethiopian Rift Valley. This divided the Ethiopian highlands into the Western Highlands and the Southeastern Highlands.

In the quaternary period, the earth experienced a marked climatic change resulting in rains known as the Pluvian Rains in Africa. During this period the Ethiopian plateaus were affected by heavy erosion.

Later on, the heavy rains were replaced by a dry climate which increased the rate of evaporation. As a result the rift valley lakes were reduced in size.

Within the Afar depression, there was believed to be a large lake. Due to absence of rivers flowing into the lake and a continuous rate of evaporation, it disappeared. Finally, salt, potash and pockets of saline water were left behind.