Maasai warriors stride across the golden grass plains at the foot of Ol doinyo Lengai - the Maasai's 'Mountain of God'. Ol doinyo Lengai is the only active volcano in the Gregory Rift, an important section of the eastern branch of Africa's Great Rift Valley system that stretches from northern Kenya into Northern Tanzania.Ol doinyo Lengai rises 7,000 feet above the surrounding plains to stand 9,400 feet high. The last explosive eruption took place in 1966 but many small-scale eruptions within its summit crater have occurred since 1983.