Irruputuncu

Geography & Climate

Irruputuncu is located in Chile-Bolivia, within the Central Andean Volcanic Arc of the broader South America Volcanic Regions. Situated at 20.73° S, 68.55° W in the Southern Hemisphere, the volcano lies within a tropical climate zone. At 5,163 meters above sea level, Irruputuncu reaches well into the permanent snow and ice zone. Glaciers and snowpack on the upper slopes create the potential for lahars — destructive volcanic mudflows — during eruptions, as heat rapidly melts ice and snow. The volcanic landform is characterized as a composite, which describes the physical shape and structure of the volcanic edifice as observed from the surface.

Geological Context

Irruputuncu sits in a subduction zone, where one tectonic plate dives beneath another, creating intense heat and pressure that generates magma. Subduction zones are responsible for many of the world's most explosive volcanoes and deadliest eruptions. For communities in Chile-Bolivia near Irruputuncu, this tectonic setting means the volcano is capable of producing powerful explosive eruptions, pyroclastic flows, and lahars that can threaten populated areas within tens of kilometers of the summit. The dominant rock type is andesite / basaltic andesite, a dark, fine-grained volcanic rock that forms from rapidly cooling, low-viscosity lava. Basaltic eruptions tend to be less explosive and produce fluid lava flows that can travel long distances. While less immediately dangerous than explosive eruptions, basaltic lava flows can destroy structures and infrastructure in their path, and volcanic gases released during these eruptions can affect air quality over a wide area.

Eruption History Summary

Irruputuncu has 2 recorded eruptions in the geological database, spanning from 1989 CE to 1995 CE. The most powerful recorded event was an explosive event producing ash plumes up to several kilometers in 1995 CE, reaching VEI 2 on the Volcanic Explosivity Index. These eruptions span roughly 6 years of volcanic history. The most recent eruption in 1995 CE places this volcano within the modern era of volcanological observation.

GVP Reference Summary

Irruputuncu is a small stratovolcano that straddles the Chile/Bolivia border. It is the youngest and most southerly of a NE-SW-trending chain of volcanoes. It was constructed within the collapse scarp of a Holocene debris avalanche whose deposit extends to the SW. Subsequent eruptions filled much of this scarp and produced thick, viscous lava flows down the W flank. The summit complex contains two craters, the southernmost of which is fumarolically active. The first unambiguous historical eruption took place in November 1995, when phreatic explosions produced dark ash clouds.

— Smithsonian Institution, Global Volcanism Program