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 Golygin ignimbrite at 443,000 ± 8,000 years old. The Kurile Lake caldera erupted 41,500 years ago, and another small eruption occurred between 9,000 and 10,000 years ago; then in 6460–6414 BCE, a very large eruption took place, forming the present-day caldera and the Kurile Lake ignimbrite and depositing ash as far as away. This eruption has a volume of , 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; as of 2024, the most recent eruption from Ilinsky was in 1911. The caldera is filled by a lake with an area of , and a maximum depth of . The largest sockeye salmon stocks in Asia live in the lake.
Geography and structure Kurile Lake is found in the southern part of the Kamchatka Peninsula, in a rugged volcanic landscape. The region was not always part of the Kamchatka Peninsula; during the middle Pleistocene, it was an island. Georg Wilhelm Steller visited the area in 1740–1743.
Kurile Lake is formed by two basins, which are separated by a subaqueous ridge. The center part of the lake is formed by a flat basin; canyons cut into the slopes of the western side of the lake, where the Ozernaya and Kumnynk rivers open into the lake. The Etamynk and Khakytsin rivers conversely have formed an alluvial fan. The maximum depth of the lake is , with an average depth of or . Since the surface elevation is , this lake hosts a cryptodepression of .
The southern basin is deeper than the northern basin ( against the of the northern basin) and is a Holocene caldera. The nature of the northern basin is less clear; Bondarenko in 1991 supposed that it was an older, separate caldera which he named Ilinsky, but Braitseva et al. 1997 and Ponomareva et al. 2004 consider both to be the Kurile Lake caldera. This caldera has an area of about , or . In that case, the ridge that separates the two basins may be a deposit left when earthquakes preceding the caldera-forming eruption caused Ilinsky volcano to collapse. The caldera collapse was controlled by faults that parallel the lake shores. Some islands in the lake formed by slumping and others are volcanic cones; the “Heart of Alaid” (Serdtze Alaida) is a lava dome high. A number of lava domes and pyroclastic cones are found in the lake. The Severnaya bay may be an explosion crater. Lava flows from Ilinsky extend into the lake.
Ring faults, partially buried by alluvial fans and landslides, limit the caldera in the lake. A large landslide forms Glinyany Peninsula in the southeastern shore of the lake. Post-caldera activity has formed some islands in the lake and the Diky Greben volcano. Both Glinyany Peninsula and the post-caldera lava domes (Chayachii, Serdtze Alaida, Tugumynk) were affected by slumping. Approximately of sediment and volcanites bury the deposits left in the caldera by the caldera-forming eruption.
The rim of the Kurile Lake caldera is best expressed at Ilinsky volcano and south and northwest thereof. Close to the lake, two Pleistocene caldera rims can be found and there may be more. The volcanoes Diky Greben, Ilinsky, Kambalny, Kosheleva, and Zheltovsky surround Kurile Lake. Diky Greben formed after the eruption of Kurile Lake.
Gravimetry indicates that there is still a magma chamber beneath Kurile Lake at a depth of about . This magma chamber is about wide.
Geology The Pacific Plate subducts at a pace of about beneath the Okhotsk Plate and Asian Plate. This subduction is responsible for the Kamchatka-Kuril Trench as well as for volcanism in Kamchatka. The Wadati-Benioff Zone lies about beneath Kurile Lake and there is a slab window under the volcano that might be responsible for its activity.
Kurile Lake is included in the Eastern Volcanic Zone of Kamchatka, away from the trench. It is one of the two or three volcanic zones of Kamchatka, the other ones being the Central Depression and the Sredinny Range. Only the first two have had historical activity. The neighbouring volcano Ilinsky was active in 1911, and Zheltovsky was active in 1923. Hydrothermal activity may still be ongoing in the lake.
The oldest volcanoes of the Pauzhetka structure may be of Oligocene-Miocene age; during that time, the area was in the sea. The sedimentary Paratunka Formation and the Kurilsky complex were deposited during that time; they are exposed east and southwest of Kurile Lake. About of basaltic rocks were erupted during the Miocene-Pliocene. The Pauzhetka depression formed during the Pliocene or Pleistocene and was most likely accompanied by the eruption of the Golygino ignimbrite. The eruption of this ignimbrite occurred 443,000 ± 8000 years ago. Afterwards, a resurgent dome named the Kambalny ridge formed in the Pauzhetka structure, as well as a proto-Ilinsky volcano.
Local The basement in the area is formed by Miocene-Pliocene sedimentary rocks and volcanic rocks. During the Pleistocene, calderas, lava plateaus, and somma volcanoes like pre-Ilinsky stratovolcanoes formed in the area.
One caldera that formed in the area is the Pauzhetka Caldera, of middle Pleistocene age. , the possibility that a later caldera existed in the Pauzhetka caldera was considered. Kurile Lake is located in the eastern part of this Pauzhetka caldera, which has dimensions of . In the center of the Pauzhetka caldera lies a -wide depression that covers an area of .
Regional explosive activity Southern Kamchatka has been the site of explosive eruptions during history; the Ksudach volcano north of Kurile Lake had five caldera forming eruptions during the Pleistocene and Holocene. The time period between 6400 and 6600 BCE was especially active, with caldera-forming eruptions including the one that formed Kurile Lake.
Kurile Lake is not the only volcano in Kamchatka with major explosive eruptions during the Holocene that exceeded VEI 5; three other such eruptions occurred at Ksudach volcano and one at Karymsky volcano.
Composition Volcanic rocks of Kurile Lake range from basaltic andesite to rhyolite. They contain small-to-medium amounts of potassium.
Rhyolite makes up the bulk of the eruption products of Kurile Lake. Minerals contained include plagioclase, orthopyroxene, clinopyroxene, magnetite, and hornblende, in decreasing order of importance. The ash becomes white away from the vent, while near-vent deposits are often yellow.
Environment
Vegetation around the caldera consists mostly of bush and forest. At the edge of the lake there is no macrovegetation.
Vegetation in Kamchatka overall consists mostly of alder bushes, pine, and stone birch. Along valleys, cottonwood and willow can be found as well. In 1998, Kurile Lake had the highest density of brown bears of Kamchatka, and possibly of the entirety of Russia. The lake is a nature reserve.
Lake
The Kurile Lake caldera is filled by the Kurile crater lake, covering a surface area of to . A lake existed already before the Kurile Lake caldera-forming eruption. The present-day lake has a volume of and a catchment of and is surrounded by steep shores. Water remains in the lake for about eighteen years.
In June 2011, a water temperature of was measured. The lake waters are oligotrophic. The Ozernaya River drains the lake to the Sea of Okhotsk. Reports in 1923 indicate that the lake was formerly up to higher than today, possibly because lava flows dammed its outlet. At least two other shorelines are found above the current water level. The caldera lake may have suffered a catastrophic outburst flood in the past.
Diatoms form most of the phytoplankton, with Cyclotella, Melosira, Stephanodiskus, and Synedra. Dominant copepod species in summer 2011 include Cyclops scutifer and the dominant cladocerans Daphnia longiremis. Other species as well as rotifers are also present; they constitute sources of food for sockeye salmons. A number of annelid species are also found, many of the species that are found in neighboring waters cannot be found in the lake. The chironomid midge Chaetocladius tatianae is endemic to the Kurile Lake watershed.
Sockeye salmon fisheries are present at the lake. The lake is a major nursery for this species of fish. The number of fish in the lake ranges from 260,000 to over 6 million. The stocks found at Kurile Lake are the largest in Asia. Fishing of the salmon of the Ozernaya River has been regulated to allow their reproduction and to conserve bear populations. The lake is part of the Kamchatka National Reserve.
Eruptive history
The idea that pumice around Kurile Lake was formed by an eruption in the area of the lake was first suggested by Boris Piip in 1947. Later research identified this pumice as the product of the caldera-forming eruption, although some skepticism remains, which considers this pumice 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, away from Kurile Lake, and possibly Lake El′gygytgyn.
The Kurile Lake caldera forming eruption, also known as "KO", occurred in 6460–6414 BCE. 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 , corresponding to a volcanic explosivity index of 7 and comparable to the 1815 eruption of Tambora.The 7600 (14C) year BP Kurile Lake caldera-forming eruption ... - CORE Other volcanoes with such large eruptions during the Holocene include Baitoushan, Crater Lake and Kikai.