It is the largest volcano caldera in Kenya and the second largest volcano caldera in Africa. Farmland occupies its flanks. The crater is located on the floor of the Rift Valley.
The volcano formed about 200,000 years ago and the prominent 12 x 8 km caldera formed about 8000 years ago. Menengai is located 10 km (6 mi) north of Nakuru.
The caldera floor is covered with numerous post caldera lava flows. The Menengai volcano is considered one of the best-preserved Krakatau-style calderas in the world. Menengai has very little sediment in the caldera which is a thick mass of lava boulders and inaccessible ridges. Volcanic activity continues and is used for geothermal power generation.