the volcanism appear to come from fissure vents and the volcanoes have been affected by faulting. these deposits reach thicknesses of and also occur on neighbouring volcanic centres. purupuruni has formed on the rim of a depression, which is surrounded by eroded quaternary volcanoes and appears to be a wide caldera. the volcano lies east-southeast from yucamane volcano and just south of the mauri river; the mauri river is part of the lake titicaca watershed.