Oldoinyo Lengai, Tanzania: Earth's Only Active Carbonatite Volcano

摘要

The cylindrical cone of Oldoinyo Lengai (2,880 m) rises spectacularly above the Gregory Rift Valley, northern Tanzania. Lengai is Earth's only known active carbonatite volcano and has been widely studied as it includes chemically unique lava flows (Dawson et al., 1990). The mountain is situated wholly within the rift, close to the prominent, western escarpment (Fig. 2). The rift valley in this area is a rugged, sparsely populated region, part of the traditional tribal area occupied by the Maasai who named the volcano "Mountain of Cod". From a distance, the pale grey-white lavas and ashes that cloak the uppermost slopes resemble the ice capped summit of Kilimanjaro, visible some 150 km to the southeast. The climate in this part of the rift valley is hot and dry almost all year round; the semi-desert environment contrasts with the fertile plains and forested slopes associated with volcanic peaks on the adjacent plateaus.