Arjuno-Welirang

Geography & Climate

Arjuno-Welirang is located in Indonesia, within the Sunda Volcanic Arc of the broader Sunda-Banda Volcanic Regions. Situated at 7.73° S, 112.58° E in the Southern Hemisphere, the volcano lies within a tropical climate zone. At 3,343 meters above sea level, Arjuno-Welirang rises above the surrounding terrain into montane or subalpine conditions. The elevation creates distinct ecological zones along its flanks, from forested lower slopes to exposed rocky terrain near the summit. 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

Arjuno-Welirang 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 Indonesia near Arjuno-Welirang, 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

Arjuno-Welirang has 3 recorded eruptions in the geological database, spanning from 1950 CE to 1991 CE. The most powerful recorded event was an explosive event producing ash plumes up to several kilometers in 1950 CE, reaching VEI 2 on the Volcanic Explosivity Index. These eruptions span roughly 41 years of volcanic history. The most recent eruption in 1991 CE places this volcano within the modern era of volcanological observation.

GVP Reference Summary

The Arjuno and Welirang volcanoes anchor the SE and NW ends, respectively, of a 6-km-long line of volcanic cones and craters. The complex overlies most of the Gunung Ringgit edifice, whose summit is about 3 km NE from the main ridge. Pyroclastic cones are located on the north flank of Gunung Welirang and along an E-W line cutting across the southern side of Gunung Arjuno that extends to the lower SE flank. Fumarolic areas with sulfur deposition occur at several locations on Welirang.

— Smithsonian Institution, Global Volcanism Program