The
Gregory Rift is the eastern branch of the
East African Rift fracture system. The rift is being caused by the separation of the
Somali plate from the
Nubian plate, driven by a
thermal plume. Although the term is sometimes used in the narrow sense of the
Kenyan Rift, the larger definition of the Gregory Rift is the set of faults and
grabens extending southward from the
Gulf of Aden through
Ethiopia and
Kenya into Northern
Tanzania, passing over the local uplifts of the Ethiopian and Kenyan domes. Ancient fossils of early
hominins, the ancestors of humans, have been found in the southern part of the Gregory Rift.