Observations on changes in the active crater of Ol Doinyo Lengai from 1960 to 1988
Drastic changes in the morphology of the summit crater of Ol Doinyo Lengai volcano have occurred over the last 3 decades. The wide flat-floored crater that persisted between 1960 and mid 1966 was filled in with volcanic ash during the explosive eruption of August–September 1966. Soon after, a deep narrow pit crater was formed, probably by collapse along circular fractures. This remained essentially unchanged until early 1983, when eruptive activity was resumed in its floor. Since then, frequent episodes of activity have occurred, with the eruption of highly fluid lava that has built up the level of the crater floor. The crater in 1988 was wide and relatively shallow, while small scale activity continued to take place.