Irruputuncu is a stratovolcano which straddles the border between Chile and Bolivia. It is a relatively small peak, lying within the collapse scarp of a debris avalanche from earlier in the Holocene. Succeeding eruptions filled much of this scarp and produced thick, viscous lava flows the western flank. Irruputuncu volcano is 5,163 m high and had two craters on top, with the one to the south displaying fumaroles. The first eruption in recorded history occurred in 1995 in the form of a phreatic eruption.