The 'Great Rift Valley' is one of the geological wonders of the world, a name given by the British Explorer John Walter Gregory in the late 1800s for the continuos geographic trench that runs from Syria in the north through to Mozambique in the south, a distance of roughly 6,000 kilometres.
The rifting process is the start of an ocean formation. As a valley (such as the Rift Valley) continues to split, it opens up to the oceans, allowing sea water to enter the valley (eg The Red Sea). As the plates continue to spread, the sea widens to form an Ocean.
The modern geological name for the Rift is The East African Rift System or EARS. This system, containing separate, yet related rift and fault systems is an area where tectonic forces are splitting apart an established plate. It is essentially a fracture in the earth's surface that is continuing to widen over time. This 'rifting' will create a 'new' plate to the west, called the Nubian (African) plate; and a smaller plate moving to the east called the Somalian Plate. These two plates are moving away from one another, as well as away from the Arabian Plate to the north. The boundary of these three plates in northern Ethiopia is called the Afar Triple Junction.
Further south, in East Africa, the Rift Valley divides into two - the Western Rift Valley and the Eastern Rift Valley
This whole system comprises of a number of rift features; the oldest and most defined is in the Afar region of Ethiopia, known as the Ethiopian Rift. A series of rifts are also found further south, including the western 'Albertine Rift' which is edged by some of the highest African mountains such as Rwenzoris, Virunga Moutnains, and Mitumba Mountains. This Western Rift in Uganda, containing the East African Great Lakes Albert, Edward, Kivu, and Tanganyika.
Lake Victoria lies in the basin between the Western and Eastern Rift systems.
The Eastern Rift Valley runs south from Ethiopia, bisecting Kenya in half along a line slightly west of Nairobi, and continues south into Tanzania. The lowest part of the valley floor is near Lake Turkana, where there are no escarpments or valley walls. Heading further south, the cliffs are very evident, over 6,000ft near Lakes Baringo, Nakuru, Elmentaita and Naivasha. The lakes in the eastern rift are shallow, and have no outlet to the sea leading them to have a high mineral content due to evaporation leaving salts from the eroded alkaline base rocks behind. Lakes Magadi and Natron have high concentrations of Soda (Sodium Carbonate), Lakes Elmentaita, Bogoria and Nakuru are highly alkaline. This alkalinity is an ideal breeding ground for algae, which in turn provides a food source for a wide variety of birds and fish, including the iconic Lesser and Greater Flamingos.
A number of active and semi-active volcanos are located in the Rift Valley system, including Mt Longonot and Lengai.