an active volcano in Tanzania (East Africa) in the Eastern Rift. It is composed of andesite and trachydolerite lavas and leucite-nepheline tuffs. The caldera, which is up to 1,300 m deep, is open in the east; near its western wall is an active cone, 3,669 m in elevation. The highest elevation is on the caldera’s western ridge (4,567 m). On the lower slope of the main cone are several secondary slag cones and craters. There are lakes ringed with lava on the eastern and southern slopes. Mount Meru last erupted in 1910. Shrub savanna and savanna forests grow on slopes with elevations up to 1,100 m; higher are secondary forests and plantations of tropical crops. Above 1,800 m are tropical rain forests, high-mountain meadows, and cliffs.