Lengai, Ol Doinyo (Tanzania)
Status Unknown Eruption 2019 2962m
Stratovolcano (Rift zone / Continental crust (> 25 km))
The symmetrical Ol Doinyo Lengai is the only volcano known to have erupted carbonatite tephras and lavas in historical time. The prominent stratovolcano, known to the Maasai as "The Mountain of God," rises abruptly 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. Historical 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 have changed dramatically during the course of historical eruptions, ranging from steep crater walls about 200 m deep in the mid-20th century to shallow platforms mostly filling the crater. Long-term lava effusion in the summit crater beginning in 1983 had by the turn of the century mostly filled the northern crater; by late 1998 lava had begun overflowing the crater rim.
A herd of wildebeasts grazes in the foreground, oblivious to an explosive eruption from Tanzania's Ol Doinyo volcano in 1966. Explosive activity began in August 1966, near the end of an eruption beginning in 1960 that consisted of quiet emission of lava flows in the summit crater. Ash deposits from previous eruptions whiten the volcano's slopes like snow. The symmetrical Ol Doinyo Lengai stratovolcano is the only volcano known to have erupted carbonatite tephras and lavas in historical time.
Photo by Gordon Davies, 1966 (courtesy of Celia Nyamweru, Kenyatta University).
Last updated 2019-08-25 10:00:03