Banua Wuhu

Geography & Climate

Banua Wuhu is located in Indonesia, within the Sangihe Volcanic Arc of the broader Western Pacific Volcanic Regions. Situated at 3.15° N, 125.44° E in the Northern Hemisphere, the volcano lies within a tropical climate zone. With an elevation of -5 meters — below sea level — Banua Wuhu is a submarine or submerged volcanic feature. Submarine volcanoes make up the majority of Earth's volcanic activity, though most eruptions go unobserved beneath the ocean surface. 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

Banua Wuhu 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 Banua Wuhu, 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

Banua Wuhu has 7 recorded eruptions in the geological database, spanning from 1835 CE to 1968 CE. The most powerful recorded event was a severe eruption capable of regional ash fall and pyroclastic flows in 1918 CE, reaching VEI 3 on the Volcanic Explosivity Index. This eruption frequency indicates a moderately active volcanic system with periodic reawakenings. The most recent eruption in 1968 CE places this volcano within the modern era of volcanological observation.

Significance

With a maximum recorded VEI of 3, Banua Wuhu 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 7 recorded eruptions on file, Banua Wuhu has enough documented activity to help scientists identify patterns in its eruptive behavior. Given its recent activity, Banua Wuhu is closely monitored by geological survey organizations to provide early warning of future unrest.

GVP Reference Summary

The submarine Banua Wuhu volcanic cone lies ~600 m off the western coast of Mahengatang Island, the emergent summit of a large submarine edifice, in the Sangihe Islands. Several ephemeral islands were constructed during the 19th and 20th centuries. An island 90 m high was formed in 1835, but had eroded to only a few rocks by 1848. Another island formed in 1889 was 50 m high in 1894. Five craters were reported during an eruption that built an island in 1904. An island that formed in 1919 had disappeared by 1935. Bathymetry shows shallow water over an area larger than Mahengatang Island towards the W (Haryanto, 2020). Satellite imagery frequently shows two sources of discolored water in the area, and it is a popular location for divers, who report sulfur odors and bubbling.

— Smithsonian Institution, Global Volcanism Program