The Rift Valley stretches some 6000 km from Dead Sea in the Middle East through the Red Sea down to Mozambique through Eastern Africa. This Rift was formed some 15 Million Years ago due to tectonic movement. The formation of rifts is usually accompanied by volcanic activity. Huge volcanoes were formed and the surrounding land got covered by layers and layers of molten lava.

The cones finally collapsed and in process the second largest caldera with 40 km diameter was formed in the Ngorongoro Highlands. Kilimanjaro, Mt. Kenya, Mt. Elgon, Ruwenzori and Mt. Meru are situated along the intersections of important tectonic lines. They were formed between 3 million and 1.5 million years ago, and their cones reached heights of over 6000 m. When the cones finally collapsed they left huge calderas behind. Due to erosion the cone shape and the caldera walls have changed. While the cone shape of Mt. Meru and Longonot is quite intact, the cone and the caldera of Mt. Kenya is hardly recognizable and present itself as a series of jagged peaks.

The last witness in present day Rift valley of volcanic activity is the Oldonyo Lengai, “the mountain of god “. This 2000m high volcano is still active and last major eruption was in 1966, while the last smaller eruption was witnessed in 2007.