 The terrain is cut by several different fault systems; one of these, the northeastward striking Sepina fault has been seismically active in the 20th and 21st centuries and seems to have controlled the development of the Ampato and Sabancaya volcanoes.Ampato has erupted different volcanic rocks at different stages, with the earliest ones generating andesite and dacite and which define a potassium-rich suite.The rocks contain amphibole, biotite, iron oxide, olivine, plagioclase, pyroxene and titanium oxide.