Reventador is part of a chain of volcanoes in the Cordillera Real, much further east than the main volcanic axis of the region. The volcano rises above the jungles of the western Amazon basin and the flanks are densely clad in forests. The volcano has a caldera that is across; there is a wide gap in the caldera wall to the east, formed by a collapse of the structure. There is an unvegetated stratovolcano rising about from inside the caldera, and this is the main seat of current volcanic activity. The lavas are andesitic.