Rinjani

Geography & Climate

Rinjani is located in Indonesia, within the Sunda Volcanic Arc of the broader Sunda-Banda Volcanic Regions. Situated at 8.42° S, 116.47° E in the Southern Hemisphere, the volcano lies within a tropical climate zone. Standing at 3,726 meters above sea level, Rinjani towers above the alpine zone, where vegetation gives way to bare rock, snow, and ice for much of the year. The high elevation means the upper slopes experience significantly colder temperatures than surrounding lowlands. 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

Rinjani 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 Rinjani, 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

Rinjani has 20 recorded eruptions in the geological database, spanning from 1257 CE to 2016 CE. The most powerful recorded event was a super-colossal eruption, among the largest in recorded geological history in 1257 CE, reaching VEI 7 on the Volcanic Explosivity Index. Notable eruptions include 1994 CE (VEI 3), 1257 CE (VEI 7). With an average interval of roughly 38 years between eruptions over a span of 759 years, this is one of the more frequently active volcanoes in the database. This persistent activity suggests a robust and well-supplied magma system beneath the volcano. With eruptive activity as recently as 2016 CE, Rinjani remains an actively monitored volcano.

Significance

Rinjani has produced at least one eruption of VEI 7 or higher, placing it among the most powerful volcanic systems ever documented on Earth. Eruptions of this magnitude eject hundreds of cubic kilometers of material, can cause volcanic winters lasting years, and have historically led to crop failures and famine across continents. Its 20 recorded eruptions make it one of the most prolific volcanoes in our database, reflecting a persistent and well-documented eruptive history that has provided volcanologists with extensive data for understanding eruption patterns and forecasting future activity. Given its recent activity, Rinjani is closely monitored by geological survey organizations to provide early warning of future unrest.

GVP Reference Summary

Rinjani volcano on the island of Lombok rises to 3726 m, second in height among Indonesian volcanoes only to Sumatra's Kerinci volcano. Rinjani has a steep-sided conical profile when viewed from the east, but the west side of the compound volcano is truncated by the 6 x 8.5 km, oval-shaped Segara Anak (Samalas) caldera. The caldera formed during one of the largest Holocene eruptions globally in 1257 CE, which truncated Samalas stratovolcano. The western half of the caldera contains a 230-m-deep lake whose crescentic form results from growth of the post-caldera cone Barujari at the east end of the caldera. Historical eruptions dating back to 1847 have been restricted to Barujari cone and consist of moderate explosive activity and occasional lava flows that have entered Segara Anak lake.

— Smithsonian Institution, Global Volcanism Program