Caldera (, ), also spelled "" and "", is a

caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption. An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the str ...

system located in the centre of Simushir island, in the central

Kuril Islands The Kuril Islands or Kurile Islands are a volcanic archipelago administered as part of Sakhalin Oblast in the Russian Far East. The islands stretch approximately northeast from Hokkaido in Japan to Kamchatka Peninsula in Russia, separating the ...

, Russia. The volcano is named after , a scientist of the

Academy of Sciences of the Soviet Union The Academy of Sciences of the Soviet Union was the highest scientific institution of the Soviet Union from 1925 to 1991. It united the country's leading scientists and was subordinated directly to the Council of Ministers of the Soviet Union (un ...

Geology

The Zavaritski volcano contains three nested calderas, measuring , and in diameter. The youngest caldera, which is partially filled by Lake , was formed during the

Holocene The Holocene () is the current geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...

and features several young

volcanic cones Volcanic cones are among the simplest volcanic landforms. They are built by ejecta from a volcanic vent, piling up around the vent in the shape of a cone with a central crater. Volcanic cones are of different types, depending upon the nature and s ...

and

lava domes In volcanology, a lava dome is a circular, mound-shaped protrusion resulting from the slow Extrusive rock, extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6 ...

. The lake surface sits at an elevation of above sea level, with the lake bottom at ''below'' sea level. Lake sediments overlying

pumice Pumice (), called pumicite in its powdered or dust form, is a volcanic rock that consists of extremely vesicular rough-textured volcanic glass, which may or may not contain crystals. It is typically light-colored. Scoria is another vesicula ...

deposits indicate that a previous caldera lake surface existed above sea level. The last reported explosive eruption was recorded in November 1957. This destroyed a diameter cone 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 a wide, high dome.

1831 eruption

Research indicates that Caldera may have been the source of a high-magnitude explosive eruption that occurred in 1831, during the

Northern Hemisphere The Northern Hemisphere is the half of Earth that is north of the equator. For other planets in the Solar System, north is defined by humans as being in the same celestial sphere, celestial hemisphere relative to the invariable plane of the Solar ...

summer. Evidence for the eruption includes

sulfate The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many ...

peaks in polar

ice cores An ice core is a core sample that is typically removed from an ice sheet or a high mountain glacier. Since the ice forms from the incremental buildup of annual layers of snow, lower layers are older than upper ones, and an ice core contains i ...

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 , coincided with fluctuations in the Indian and African

monsoons A monsoon () is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with annual latitudinal oscil ...

, and preceded major famines (including the famine of 1832 in India). However, the source of this major eruption has remained a mystery. The researchers, led by volcanologist William Hutchison, conducted

geochemical Geochemistry is the science that uses the tools and principles of chemistry to explain the mechanisms behind major geological systems such as the Earth's crust and its oceans. The realm of geochemistry extends beyond the Earth, encompassing the ...

analyses of several Greenland ice cores. They found, coinciding with the sulphate peaks from the 1831 eruption, microscopic layers of

tephra Tephra is fragmental material produced by a Volcano, volcanic eruption regardless of composition, fragment size, or emplacement mechanism. Volcanologists also refer to airborne fragments as pyroclasts. Once clasts have fallen to the ground, ...

that chemically matched deposits from the most recent

Plinian Plinian eruptions or Vesuvian eruptions are volcanic eruptions characterized by their similarity to the eruption of Mount Vesuvius in 79 AD, which destroyed the ancient Roman cities of Herculaneum and Pompeii. The eruption was described in a le ...

eruption, dated to the early 19th century. Modelling suggests that the eruption could have been a VEI 5/6-magnitude eruption event. The reconstructed

radiative forcing Radiative forcing (or climate forcing) is a concept used to quantify a change to the balance of energy flowing through a planetary atmosphere. Various factors contribute to this change in energy balance, such as concentrations of greenhouse gases ...

of the eruption is comparable to the

1991 eruption of Mount Pinatubo The 1991 eruption of Mount Pinatubo in the Philippines' Luzon Volcanic Arc was the second-largest volcanic eruption of the 20th century, behind only the 1912 eruption of Novarupta in Alaska. Eruptive activity began on April 2 as a series of p ...

, and may account for the climatic cooling observed between 1831–1833.

References

External links

* * Aerial image retrieve fro
NASA Technical Reports Server
on 19 April 2007. {{Kuril Islands Simushir Active volcanoes Volcanic crater lakes Calderas of Russia Volcanoes of the Kuril Islands Pleistocene calderas Holocene calderas

Geology

1831 eruption

See also

References

External links