Akan Volcanic Complex is a

volcanic group A volcanic group, depending on context, is either (1) a group of related volcanoes in the form of volcanic fields, volcanic complexes and cone clusters, or (2) a stratigraphic group consisting of volcanic strata In geology and relate ...

volcano A volcano is commonly defined as a vent or fissure in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most oft ...

es that grew out of the Akan

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 ...

. It is located within

Akan National Park is a national park located on the island of Hokkaidō, Japan. Along with Daisetsuzan National Park, these are the two oldest national parks in Hokkaidō. The park was established December 4, 1934. Akan is an area of volcanic craters and forests ...

, about 50 km Northwest of

Kushiro is a city in Kushiro Subprefecture on the island of Hokkaido, Japan. Located along the coast of the North Pacific Ocean, it serves as the subprefecture's capital and it is the most populated city in the eastern part of the island. History An ...

in eastern

Hokkaidō is the second-largest island of Japan and comprises the largest and northernmost prefecture, making up its own region. The Tsugaru Strait separates Hokkaidō from Honshu; the two islands are connected by railway via the Seikan Tunnel. The ...

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

Description

A number of peaks are arranged around the rim of

Lake Akan is a lake in Kushiro, Hokkaidō, Japan. It is located in Akan National Park and is a Ramsar Site. History Volcanic activity formed the lake some 6,000 years ago, when a lava dam was formed. The lake used to have a clarity of 8–9 meters in t ...

( Akan-ko), which fills a 24×13 km caldera, the tallest being Me-Akan (Meakan), O-Akan (Oakan) and Akan-Fuji. Oakan is prominently located at the northeast side of the caldera, while Meakan occupies the opposite, southwest side, in a cluster of nine

stratovolcanoes A stratovolcano, also known as a composite volcano, is a typically conical volcano built up by many alternating layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a ...

that include Akan-Fuji, one of many symmetrical Japanese volcanoes named after the renowned

Mount Fuji is an active stratovolcano located on the Japanese island of Honshu, with a summit elevation of . It is the highest mountain in Japan, the second-highest volcano on any Asian island (after Mount Kerinci on the Indonesian island of Sumatra), a ...

, and Fuppushi volcano (a.k.a. Fuppushi-dake, not to be confused with Mount Fuppushi, which is located in Southwestern Hokkaido).

Volcanology

The Akan caldera was formed 31,500 years ago. Its elongated shape is due to its incremental formation during major explosive eruptions, from the early to the mid-

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

periods. The Nakamachineshiri crater of Meakan volcano was formed during a major eruption about 13,500 years ago. The Me-Akan group of nine overlapping cones on the eastern side of Lake Akan has had mild eruptions since the beginning of the 19th century. The last eruption of this historical volcano was in 2008. Oakan, Meakan, Furebetsu and Fuppushi are the major post-caldera volcanoes of the Akan volcanic complex. Me-Akan is one of the most active volcanoes of Hokkaido. Its summit contains the active craters of Ponmachineshiri and Naka-Machineshiri, sites of frequent

phreatic ''Phreatic'' is a term used in hydrology to refer to aquifers, in speleology to refer to cave passages, and in volcanology to refer to a type of volcanic eruption. Hydrology The term phreatic (the word originates from the Greek , meaning "well" ...

eruptions in historical time. Akan-Fuji and O-Akan have not erupted in historical time. Akan is rated with a

volcanic explosivity index The volcanic explosivity index (VEI) is a scale used to measure the size of explosive volcanic eruptions. It was devised by Christopher G. Newhall of the United States Geological Survey and Stephen Self in 1982. Volume of products, eruption c ...

of 4 on the Smithsonian VEI scale, the scale's fourth-highest score, based on the volcano's largest known eruption, around 7050 BC. Following are prominent features of Akan:

Cones

*Me-Akan-Dake (

Mount Meakan is an active stratovolcano located in Akan National Park in Hokkaidō, Japan. It is the tallest mountain in the Akan Volcanic Complex. The volcano consists of nine overlapping cones that grew out of the Akan caldera, on the shores of Lake Akan ...

) (1499 m) Stratovolcano *Akan Fuji (Akan-Fuji, Akan-Huji) (1476 m) Stratovolcano *Kita-Yama (1400 m) Cone *O-Akan-Dake (

Mount Oakan is a stratovolcano located in Akan National Park in Hokkaidō, Japan. Geography and geology Mount Oakan sits in the Akan caldera northeast of Lake Akan. The volcano rises some above the surrounding terrain. The top of the volcano is above se ...

) (1371 m) Stratovolcano *Kenga-Mine Cone 1336 m *Nishi-Yama (Nisi-Yama) (1300 m) Cone *Fuppushi (Huppusi) (1226 m) Stratovolcano *Miname-Dake (1217 m) Stratovolcano *Higashi-Dake (Higasi-Dake) (1140 m) Cone *Furebetsu (Hurebetu) (1098 m) Stratovolcano *Kobu-Yama Cone *Futatsu-Dake Pyroclastic cone

Craters

*Nakamachineshiri (Nakamatineshiri) Crater *Ponmachineshiri (Ponmatinesiri) Crater

Thermal features

*Akan-Kohan Thermal Feature

Other peaks

* Mount Ken * Mount Ahoro

References

External links

Akan Caldera
- Geological Survey of Japan {{100 Famous Japanese Mountains Volcanoes of Hokkaido Volcanic groups Pleistocene calderas Calderas of Hokkaido