The Gedamsa Caldera is a 7 x 9 km caldera in the Main Ethiopian Rift valley. The caldera has steep sides with high walls, the upper parts of which consist predominantly of rhyolitic lava flows deposited in a series of trachite ignimbrite eruptions. There are small basaltic spatter cones and fumarolic activity inside the caldera floor along with a series of (Late Pleistocene to Holocene) rhyolite and pumice deposits and a Holocene lava dome/flow.