Great Rift Valley also Rift Valley A geologic depression of southwest Asia and eastern Africa extending from the Jordan River valley to Mozambique. The region is marked by a series of faults caused by volcanic action.
rift valley n. A valley that has developed along a rift, especially one bounded by normal faults in an area of lithospheric thinning.
graben (grä'bən) Pronunciation Key
A usually elongated block of rock that is bounded by parallel geologic faults along its two longest sides, and has a lower elevation than the rock at its sides. Grabens form where rock is being pulled apart by tectonic forces. The East African Rift Valley is a graben.
rift valley
A long, narrow valley lying between two normal geologic faults. Rift valleys usually form where the Earth's lithosphere has become thin through extension associated with plate-tectonic processes. Unlike river valleys and glacial valleys that form primarily through erosional processes, rift valleys form by the subsidence of the intermediate land as the faults are pulled apart. They are on the order of thousands of kilometers long and wide. See more at normal fault.
The deep undersea valley located along the center of the mid-ocean ridge. It is associated with the crustal thinning and extensional forces that cause magma to upwell onto the ocean floor.
[grah-buh