<P> The East African Rift (EAR) is an active continental rift zone in East Africa . The EAR began developing around the onset of the Miocene, 22--25 million years ago . In the past, it was considered to be part of a larger Great Rift Valley that extended north to Asia Minor . </P> <P> The rift is a narrow zone that is a developing divergent tectonic plate boundary, where the African Plate is in the process of splitting into two tectonic plates, called the Somali Plate and the Nubian Plate, at a rate of 6--7 mm (0.24--0.28 in) annually . As extension continues, lithospheric rupture will occur within 10 million years, the Somali plate will break off, and a new ocean basin will form . </P> <P> A series of distinct rift basins, the East African Rift System extends over thousands of kilometers . The EAR consists of two main branches . The Eastern Rift Valley (also known as Gregory Rift) includes the Main Ethiopian Rift, running eastward from the Afar Triple Junction, which continues south as the Kenyan Rift Valley . The Western Rift Valley includes the Albertine Rift, and farther south, the valley of Lake Malawi . To the north of the Afar Triple Junction, the rift follows one of two paths: west to the Red Sea Rift or east to the Aden Ridge in the Gulf of Aden . </P>

The east african rift valleys are good examples of what type of plate boundary