page_title: Kurile Lake
section_title: Eruptive history
hierarchical_section_title: Kurile Lake / Eruptive history
caption_attribution_description: Русский: Кутхины Баты - памятник природы, причудливое обнажение пемз в 4 километрах от истока реки Озерная (озеро Курильское). English: Kutkhiny Baty - a pumice rock formation outcrop located 4 kilometres from the source of the River Ozernaya (Lake Kurile), near the southern tip of the Kamchatka peninsula, Russia.
context_page_description: Kurile Lake is a caldera and crater lake in Kamchatka, Russia. It is also known as Kurilskoye Lake or Kuril Lake. It is part of the Eastern Volcanic Zone of Kamchatka which, together with the Sredinny Range, forms one of the volcanic belts of Kamchatka. These volcanoes form from the subduction of the Pacific Plate beneath the Okhotsk Plate and the Asian Plate.
  Before the Kurile Lake caldera formed, the Pauzhetka caldera was active during the Pleistocene, and was the origin of the 443,000 ± 8,000 years old Golygin ignimbrite. The Kurile Lake caldera erupted 41,500 years ago, and another small eruption occurred between 9,000 and 10,000 years ago; then 6460–6414 BC a very large eruption took place, forming the present-day caldera and the Kurile Lake ignimbrite and deposited ash as far as 1,700 kilometres away. This eruption has a volume of 140–170 cubic kilometres, making it a VEI 7-class eruption and one of the largest during the Holocene. Subsequently, the volcanoes Diky Greben and Ilinsky grew around the caldera; the last eruption from Ilinsky was in 1911. The caldera is filled by a lake with an area of 76 square kilometres, and a maximum depth of 316 metres.
context_section_description: The idea that pumices around Kurile Lake were formed by an eruption in the area of the lake was first suggested by Boris Piip in 1947. Later research identified these pumices as the product of the caldera-forming eruption, although some scepticism remains, which considers these pumices as the product of fissure eruptions. An earlier Pleistocene caldera-forming eruption took place 41,500 years ago, ash deposits from this eruption are found as far away as Magadan, 1,000 kilometres (620 mi) away from Kurile Lake, and possibly Lake El′gygytgyn.
  The Kurile Lake caldera forming eruption, also known as "KO", occurred in 6460-6414 BC. It is the largest known Holocene eruption in Kamchatka. Tephra from this eruption has been found in southern Kamchatka and also Magadan in Asia. The total volume of the Kurile Lake caldera forming eruption is about 140–170 cubic kilometres (34–41 cu mi), corresponding to a volcanic explosivity index of 7 and comparable to the 1815 eruption of Tambora. Other volcanoes with such large eruptions during the Holocene include Baitoushan, Crater Lake and Kikai. The volume of the Kurile Lake eruption may have exceeded that of the Tambora eruption.
  The caldera forming eruption commenced with a phreatoplinian eruption that generated deposits of fine ash. Several yellowish rhyolitic ignimbrites were erupted, reaching a thickness of over 50 metres (160 ft). These ignimbrites filled gullies around the lake and also reach thicknesses of several tens of centimetres in the Vychenkiya River and Unkanovich River valleys. This eruption phase occurred through the lake. All these deposits were formed by the same event. Subsequently, a short eruption of lapilli and pumice consisting of dacite and rhyolite occurred, most of it falling towards the northwest; their thickness reaches 20 centimetres (7.9 in) north of the lake. Some basaltic scoria was also deposited during this phase. At this point, the vent had emerged above the water level and was generating an eruption column that deposited ash over southern Kamchatka. Eventually, the vent widened and caused the eruption column to collapse. At this point, pyroclastic flows formed and deposited the Kurile Lake ignimbrite. Reaching a thickness of 150 metres (490 ft) close to the lake, it filled valleys, overran plateaus and ridges and reached both the Pacific Ocean and the Sea of Okhotsk. The ignimbrite was highly mobile, overrunning high topographic obstacles and flowing along valleys in a complex flow pattern. The ignimbrite covered a total surface area of 1,800–1,900 square kilometres (690–730 sq mi). This ignimbrite consists of rocks ranging from basaltic andesite to rhyolite with colours ranging from white to dark. Unusually for such mixed-composition ignimbrites, the rhyolites overlie the more mafic deposits. These mafic ignimbrites are not found around the entire lake, indicating that the magma chamber was asymmetric or its contents were erupted in an asymmetric fashion. The ignimbrite contains remnants of vegetation, accretionary structures formed when the ignimbrite interacted with water, breccia probably formed when conditions at the vent changed, involving the formation of a ring vent. Fumaroles formed as the ignimbrite overran rivers. Some post-eruption alteration of the ignimbrite deposits also took place. In the lake itself, the ignimbrite is about 400 metres (1,300 ft) thick. The pumice deposits have been affected by erosion and possibly by fumarolic activity, forming structures resembling overturned boats that were named "Khutk's boats" by native settlers.
  Ash from the eruption spread west-northwest of Kurile Lake, covering a total surface of over 2,000,000 square kilometres (770,000 sq mi); it can be found at large distances from the caldera; 1-millimetre-thick (0.04 in) layers have been found in the upper reaches of the Indigirka River, 1,700 kilometres (1,100 mi) away from Kurile Lake. Thicknesses still reach several centimetres in Magadan. In the northern Kuriles, the thickness reaches several tens of centimetres. This ash is found in drilling cores in t
caption: Outcrop of pumice at Kuthiny Baty, 4 km (2.5 mi) from the lake
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