Rift Valley

In the original definition by John W. Gregory (1894) a rift valley is "a linear valley with parallel and almost vertical sides, which has fallen owing to a series of parallel faults". The typical morphology is characterized by a valley floor, between30 and 100 km wide, separated from the surrounding plateaus by huge scarps that may vary in height from a few hundreds to a few thousandsof meters.Archetypeof thismorphology is the East African rift valley, where the concept has been originally introduced. In this region the rift valley extends in a roughly north-south direction from the Afar depression, where the system of tectonic troughs joins the oceanic domains of the Red Sea and Gulf of Aden, to the Zambeziriver in Mozambique.

    The floor of the eastern arm of the Great Rift Valley houses the Kenya Lake System which covers three of Africa's most spectacular lakes(Lakes Nakuru, Bogoria and Elmenteita). 

This is an area where the Earth is splitting apart, and the lakesare nestled in the valley floor in a landscape dominatedby dramaticescarpmentsand punctuated by volcanic cones,steamingfumeroles and hotsprings. Straddling the equator, these three alkaline‘soda' lakes are the settingfor oneof the Earth'sgreatestwildlifespectacles- the feedingand movementof massive flocksof lesser flamingos. Numberingup to 4 million birds,they movebetweenthe threelakes(and furtherafield) in responseto episodicand seasonalchangesin the abundanceof the algae on whichthey feed.

    The East African Rift Systemhowever, is an excellentfield laboratoryto studya modern, actively developingrift system.

  Recently, basalteruptionsand activecrevice formationhave beenobservedin the EthiopianRift whichpermitsus to directlyobservethe initial formationof ocean basinson land. This is oneof the reasonswhy the East African Rift Systemis so interestingto scientists.Mostrifts in other parts of the world have progressedto the pointthatthey are now either underwater or have beenfilledin with sedimentsand are thushard to studydirectly.