Ol Doinyo Lengai (Oldoinyo Lengai), “Mountain of God” in the Maasai language, is an active volcano located in the Gregory Rift, south of Lake Natron on the border of Longido and Ngorongoro Districts of Arusha Region in Tanzania, Africa. Part of the volcanic system of the East African Rift, it uniquely produces natrocarbonatite lava. The 1960 eruption of Ol Doinyo Lengai led to geological investigations that finally confirmed the view that carbonatite rock is derived from magma.