Origins of the Rift Valley
The Rift Valley – a giant scar stretching some 4000 kilometres from the Red Sea down to Mozambique – is the most obvious feature of the Earth that is visble from space; a fact predicted by the first Geologist to reach it in order to make a transect to take rock samples, after leaving England in 1892 - John Walter Gregory. He actually gained his first sight of it above Naivasha, but pressed on further north to the area of Lake Baringo, because the Maasai were too agressive to travellers in this location!
Gregory believed in the theory of another geologist, a Swiss named Suess, that once there was a supercontinent named Gondwanaland and that continents have been moving apart ever since then. This was only a theory, developed from the reports and maps of explorers and fossil anomalies, but Gregory gained hard evidence in the form of a transect of rock types from east to west at the Baringo latitudes and coined the term "Rift Valley" for the new geological phenomenon he was describing. Early in the 20th Century a meteorologist, Alfred Wegener, then proposed the term 'Continental Drift' to the theory, but it took another 50 years until it was fully accepted by scientists as a correct explanation of the earth's past thousand million years of geologcal history, under the new term "Plate Tectonics"
The sides of the African Rift valley are still slowly moving apart and there are a few active volcanoes within it. The most recent to erupt was Ol Donyo Lengai – the 'Mountain of God' in Maasai – near Lake Natron in northern Tanzania, which showered its surroundings in volcanic dust in 2009. Ol Donyo Lengai, together with the chain of relatively shallow lakes from Natron through Kenya into Ethiopia, lies in the Eastern Rift, called the Gregory Rift. Two branches of the Rift encircle Lake Victoria, the western arm being much larger and with deep and very ancient lakes, such as lakes Tanganyika and Malawi, within it.
