Zavaritzki caldera

Zavaritzki caldera, wide caldera volcano with a summit of 2,008 feet (612 meters) located on Simushir Island in the Kuril Islands. The volcano is part of a system made up of three nested calderas with diameters of 10 km (6.2 miles), 8 km (5 miles), and 3 km (1.9 miles), respectively, that form Biryuzovoe Lake, and several smaller lava domes and cinder cones nearby. Zavaritzki was the site of moderate eruptions in 1923 and 1957. The volcano, however, took on increasing importance in 2024 with the publication of an ice-core study that linked the volcano’s 1831 explosion to a significant global cooling event that occurred near the end of the Little Ice Age. Zavaritzki caldera is sometimes confused with Zavaritsky, an inactive volcano on the Kamchatka Peninsula.

The explosion of Zavaritzki in 1831 released 13 million metric tons (about 14 million short tons) of sulfur into the atmosphere and was one of the largest volcanic events of the 19th century (see also Mount Tambora). The volcanic plume that resulted rose into the stratosphere, forming a layer of sulfate aerosols that led to a global temperature decrease of about 1 °C (1.8 °F). In the weeks and months after the eruption, reports emerged from across the Northern Hemisphere noting that the Sun took on blue, green, and even purple hues, which were later attributed to the scattering of sunlight passing through the aerosol layer. The eruption and its emissions altered weather patterns and caused crop failures and famines in India and Japan in the years that followed. Although the effects of the climate disruption caused by this volcano have been documented since the 1830s, the source of this disruption remained a mystery until the publication of the 2024 study.