Zavaritzki Caldera

Geography & Climate

Zavaritzki Caldera is located in Russia, within the Kuril Volcanic Arc of the broader Northwestern Pacific Volcanic Regions. Situated at 46.92° N, 151.95° E in the Northern Hemisphere, the volcano lies within a temperate climate zone. With a summit elevation of 612 meters above sea level, Zavaritzki Caldera is a moderately sized peak that remains accessible to hikers and researchers for much of the year. The volcanic landform is characterized as a caldera, which describes the physical shape and structure of the volcanic edifice as observed from the surface.

Geological Context

Zavaritzki Caldera 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 Zavaritzki Caldera, 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

Zavaritzki Caldera has 2 recorded eruptions in the geological database, spanning from 1923 CE to 1957 CE. The most powerful recorded event was a severe eruption capable of regional ash fall and pyroclastic flows in 1957 CE, reaching VEI 3 on the Volcanic Explosivity Index. These eruptions span roughly 34 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, Zavaritzki Caldera 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, Zavaritzki Caldera is closely monitored by geological survey organizations to provide early warning of future unrest.

GVP Reference Summary

The Zavaritzki volcano on Simushir Island in the central Kuril Islands contains three nested calderas 10, 8, and 3 km in diameter. The steep-walled youngest caldera was formed during the Holocene and includes several young cones and lava domes near the margins of Biryuzovoe Lake. The current lake surface is at ~40 m elevation with the bottom ~30 m below sea level, but lacustrine sediments overlying pumice deposits indicate that the surface of an earlier caldera lake lay at 200 m above sea level. A small 500-m-diameter scoria cone, sketched by Gorshkov (1958, CAVW) that reportedly grew between 1916 and 1931, formed a peninsula extending into the lake from the NE caldera wall. Explosive eruptions in 1957 removed the cone and filled much of the NW part of the lake, including emplacement of a 350-m-wide, 40-m-high dome. Hutchison et al. (2024) provided convincing evidence that Zavaritski Caldera was the source for a significant sulfur-rich eruption in 1831 CE, which was previously known only from ice core data and thought to have possibly originated from Babuyan Claro volcano.

— Smithsonian Institution, Global Volcanism Program