This is a photo of Suswa's crater rim
During the past 3 to 5 million years, faulting occured in this region and was renewed within the last million years. Suswa along with other local volcanoes such as Longonot and Menengai also erupted during this time period .
Over time a 10 km (6 mile) wide caldera was formed along with a subsidiary stratovolcano in its southern quadrant. The northern portion of Suswa subsided and a new circular crater was formed. This volcano has not erupted in historic geological time but maybe within the last 10,000 years.
More images of Suswa.
Richard J.J.,Neumann van Padang M, 1957 Africa and the Red Sea. Catalog of Active Volcanoes of the World, Rome: IAVCEI 4, p.62-64.
Images of Volcanoes To VolcanoWorld