Lengai, Ol Doinyo

About Lengai, Ol Doinyo

The symmetrical Ol Doinyo Lengai is the only volcano where the eruption of carbonatite tephras and lavas has been observed. The prominent stratovolcano, known to the Maasai as "The Mountain of God," rises above the broad plain south of Lake Natron in the Gregory Rift Valley. The cone-building stage ended about 15,000 years ago and was followed by periodic ejection of natrocarbonatitic and nephelinite tephra during the Holocene. Reported eruptions have consisted of smaller tephra ejections and emission of numerous natrocarbonatitic lava flows on the floor of the summit crater and occasionally down the upper flanks. The depth and morphology of the northern crater has changed dramatically during the course of recent observed eruptions, ranging from steep crater walls about 200 m deep in the mid-20th century to shallow platforms mostly filling the crater to lava overflowing the crater rim.