Rasshua

Geography & Climate

Rasshua is located in Russia, within the Kuril Volcanic Arc of the broader Northwestern Pacific Volcanic Regions. Situated at 47.77° N, 153.02° E in the Northern Hemisphere, the volcano lies within a temperate climate zone. With a summit elevation of 956 meters above sea level, Rasshua 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

Rasshua 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 Russia near Rasshua, 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

Rasshua has 2 recorded eruptions in the geological database, spanning from 1846 CE to 1957 CE. The most powerful recorded event was a severe eruption capable of regional ash fall and pyroclastic flows in 1846 CE, reaching VEI 3 on the Volcanic Explosivity Index. These eruptions span roughly 111 years of volcanic history. The most recent eruption in 1957 CE places this volcano within the modern era of volcanological observation.

Significance

With a maximum recorded VEI of 3, Rasshua 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. Given its recent activity, Rasshua is closely monitored by geological survey organizations to provide early warning of future unrest.

GVP Reference Summary

The elongated 6 x 13 km island of Rasshua in the central Kuriles contains three overlapping central cones within a 6 km caldera whose eastern margin is beyond the shoreline. An eroded central cone was constructed during the late Pleistocene, along with an isolated cone near the NW coast. Two Holocene cones were built within the crater of the central cone. The westernmost forms the 956 m high point of the island and is the source of lava flows that flooded the crater floor and descended to the coast. The easternmost cone, active during historical time, is truncated by a 500-m-wide crater that is breached to the SE. This crater may have formed during a violent eruption in 1846. The only other known historical eruption produced weak explosions in 1957. Fumarolic activity continues in the eastern crater and in the saddle between the two summit cones.

— Smithsonian Institution, Global Volcanism Program