Isluga

Geography & Climate

Isluga is located in Chile, within the Central Andean Volcanic Arc of the broader South America Volcanic Regions. Situated at 19.15° S, 68.83° W in the Southern Hemisphere, the volcano lies within a tropical climate zone. At 5,550 meters above sea level, Isluga 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

Isluga 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 near Isluga, 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

Isluga has 8 recorded eruptions in the geological database, spanning from 1863 CE to 1960 CE. The most powerful recorded event was an explosive event producing ash plumes up to several kilometers in 1960 CE, reaching VEI 2 on the Volcanic Explosivity Index. This eruption frequency indicates a moderately active volcanic system with periodic reawakenings. The most recent eruption in 1960 CE places this volcano within the modern era of volcanological observation.

Significance

With 8 recorded eruptions on file, Isluga has enough documented activity to help scientists identify patterns in its eruptive behavior. Given its recent activity, Isluga is closely monitored by geological survey organizations to provide early warning of future unrest.

GVP Reference Summary

The broad Isluga volcano lies 7 km W of the Chile/Bolivia border at the W end of a group of volcanoes extending to Tata Sabaya volcano in Bolivia. A stratovolcano, it contains a well-preserved, 400-m-wide summit crater at the W end of the elongated, snow-covered summit region. Numerous postglacial lava flows, many showing distinct levees, are most prominent along a broad front on the lower S flank. Activity from the summit crater was reported in the 19th and 20th centuries. A lava flow in 1878 destroyed several towns.

— Smithsonian Institution, Global Volcanism Program