| Zavaritski Caldera | |
|---|---|
 | |
| Highest point | |
| Elevation | 624 m (2,047 ft) |
| Coordinates | 46°55′N151°57′E / 46.917°N 151.950°E /46.917; 151.950 |
| Geography | |
  Zavaritski Caldera Zavaritski Caldera in Russian Far East | |
 | |
| Location | Simushir,Kuril Islands,Russia |
| Geology | |
| Mountain type | Caldera |
| Last eruption | November to December 1957 |
Zavaritski Caldera (Russian:Вулкан Заварицкого,Vulkan Zavaritskogo), also spelled "Zavaritskii" and "Zavaritsky", is acaldera system located in the centre ofSimushir island, in the centralKuril Islands, Russia. The volcano is named afterAlexander Nikolayevich Zavaritski, a scientist of theAcademy of Sciences of the Soviet Union.
The Zavaritski volcano contains three nested calderas, measuring 3 kilometres (2 miles), 8 km (5 mi) and 10 km (6 mi) in diameter. The youngest caldera, which is partially filled by LakeBiryuzovoe, was formed during theHolocene and features several youngvolcanic cones andlava domes. The lake surface sits at an elevation of 40 metres (100 feet) above sea level, with the lake bottom at30 mbelow sea level. Lake sediments overlyingpumice deposits indicate that a previous caldera lake surface existed 200 m (700 ft) above sea level.
The last reported explosive eruption was recorded in November 1957. This destroyed a 500 m (1⁄3 mi) diameter cone[1] that reportedly grew pre-eruption and had formed a peninsula extending into the lake from the northeast caldera wall. The eruption filled the northwest section of the lake, including the emplacement of a350 m (1⁄4 mi) wide, 40 m (100 ft) high dome.
Research indicates thatZavaritski Caldera may have been the source of a high-magnitude explosive eruption that occurred in 1831, during theNorthern Hemisphere summer.[2]
Evidence for the eruption includessulfate peaks in polarice cores and from historical observations of atmospheric phenomena in Japanese records (such as observations of an abnormally colored sun). It is thought that the mass injection of sulfur from the eruption caused Northern Hemisphere climate cooling of 0.5–1.0 °C (1–2 °F), coincided with fluctuations in the Indian and Africanmonsoons, and preceded major famines (including theGuntur famine of 1832 in India). However, the source of this major eruption has remained a mystery.[2]
The researchers, led by volcanologist William Hutchison, conductedgeochemical analyses of several Greenland ice cores. They found, coinciding with the sulphate peaks from the 1831 eruption, microscopic layers oftephra that chemically matched deposits from the most recentPlinianZavaritski eruption, dated to the early 19th century. Modelling suggests that the eruption could have been aVEI 5/6-magnitude eruption event. The reconstructedradiative forcing of the eruption is comparable to the1991 eruption of Mount Pinatubo, and may account for the climatic cooling observed between 1831–1833.[2]