Iliwerung

Geography & Climate

Iliwerung is located in Indonesia, within the Sunda Volcanic Arc of the broader Sunda-Banda Volcanic Regions. Situated at 8.53° S, 123.57° E in the Southern Hemisphere, the volcano lies within a tropical climate zone. With a summit elevation of 583 meters above sea level, Iliwerung is a moderately sized peak that remains accessible to hikers and researchers for much of the year. 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

Iliwerung 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 Iliwerung, 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 basalt / picro-basalt, 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

Iliwerung has 16 recorded eruptions in the geological database, spanning from 1870 CE to 2021 CE. The most powerful recorded event was a severe eruption capable of regional ash fall and pyroclastic flows in 1870 CE, reaching VEI 3 on the Volcanic Explosivity Index. This level of eruptive frequency indicates a persistently active volcanic system that warrants ongoing monitoring. With eruptive activity as recently as 2021 CE, Iliwerung remains an actively monitored volcano.

Significance

With a maximum recorded VEI of 3, Iliwerung has produced eruptions capable of generating pyroclastic flows and significant ash fall in the surrounding area. While not among the largest eruptions globally, VEI 3 events pose serious hazards to local populations and can disrupt regional air travel. With 16 recorded eruptions, Iliwerung has a substantial eruptive history that provides valuable data for understanding volcanic behavior and assessing future hazards in the Sunda-Banda Volcanic Regions region. Given its recent activity, Iliwerung is closely monitored by geological survey organizations to provide early warning of future unrest.

GVP Reference Summary

Constructed on the southern rim of the Lerek caldera, Iliwerung forms a prominent south-facing peninsula on Lembata (formerly Lomblen) Island. Craters and lava domes have formed along N-S and NW-SE lines on the complex volcano; activity has been observed at vents from the summit to the submarine SE flank. The summit lava dome was formed during an eruption in 1870. In 1948 the Iligripe lava dome grew on the E flank at 120 m elevation. Beginning in 1973-74, when three ephemeral islands were formed, submarine eruptions began on the lower ESE flank at a vent named Hobal; several other eruptions have since taken place at this vent.

— Smithsonian Institution, Global Volcanism Program