is an active
complex volcano
A complex volcano, also called a compound volcano or a volcanic complex, is a mixed landform consisting of related volcanic centers and their associated lava flows and pyroclastic rock. They may form due to changes in eruptive habit or ...
in central
Honshū
, historically known as , is the largest of the four main islands of Japan. It lies between the Pacific Ocean (east) and the Sea of Japan (west). It is the seventh-largest island in the world, and the second-most populous after the Indonesian ...
, the main island of
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 ...
. The volcano is the most active on Honshū.
The
Japan Meteorological Agency
The Japan Meteorological Agency (JMA; ''気象庁, Kishō-chō'') is a division of the Ministry of Land, Infrastructure, Transport and Tourism dedicated to the Scientific, scientific observation and research of natural phenomena. Headquartered ...
classifies Mount Asama as rank A.
It stands above
sea level
Mean sea level (MSL, often shortened to sea level) is an mean, average surface level of one or more among Earth's coastal Body of water, bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical ...
on the border of
Gunma
is a landlocked prefecture of Japan located in the Kantō region of Honshu. Gunma Prefecture has a population of 1,937,626 (1 October 2019) and has a geographic area of . Gunma Prefecture borders Niigata Prefecture and Fukushima Prefecture to t ...
and
Nagano prefecture
is a Landlocked country, landlocked Prefectures of Japan, prefecture of Japan located in the Chūbu region of Honshu. Nagano Prefecture has a population of 2,007,682 () and has a geographic area of . Nagano Prefecture borders Niigata Prefecture ...
s. It is included in ''
''.
Geology
Mount Asama sits at the conjunction of the
Izu–Bonin–Mariana Arc and the
Northeastern Japan Arc
The Northeastern Japan Arc, also Northeastern Honshū Arc, is an island arc on the Pacific Ring of Fire. The arc runs north to south along the Tōhoku region of Honshū, Japan. It is the result of the subduction of the Pacific plate underneath ...
.
The mountain is built up from non-alkali mafic and pyroclastic volcanic rocks dating from the
Late Pleistocene
The Late Pleistocene is an unofficial Age (geology), age in the international geologic timescale in chronostratigraphy, also known as the Upper Pleistocene from a Stratigraphy, stratigraphic perspective. It is intended to be the fourth division ...
to 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 ...
.
The main rock types are
andesite
Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predomina ...
and
dacite
Dacite () is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyolite. ...
.

Scientists from the
University of Tokyo
The University of Tokyo (, abbreviated as in Japanese and UTokyo in English) is a public research university in Bunkyō, Tokyo, Japan. Founded in 1877 as the nation's first modern university by the merger of several pre-westernisation era ins ...
and
Nagoya University
, abbreviated to or NU, is a Japanese national research university located in Chikusa-ku, Nagoya.
It was established in 1939 as the last of the nine Imperial Universities in the then Empire of Japan, and is now a Designated National Universit ...
completed their first successful imaging experiment of the interior of the volcano in April 2007. By detecting sub-atomic particles called
muons
A muon ( ; from the Greek letter mu (μ) used to represent it) is an elementary particle similar to the electron, with an electric charge of −1 '' e'' and a spin of ''ħ'', but with a much greater mass. It is classified as a le ...
as they passed through the volcano after arriving from space, the scientists were able gradually to build up a picture of the interior, creating images of cavities through which lava was passing deep inside the volcano.
A University of Tokyo
volcano observatory is located on the mountain's east slope. Volcanic gas emissions from this volcano are measured by a
Multi-Component Gas Analyzer System
A multi-component gas analyzer system (Multi-GAS) is an instrument package used to take real-time high-resolution measurements of volcanic gases. A Multi-GAS package includes an infrared spectrometer for carbon dioxide, CO2, two electrochemical sen ...
, which detects pre-eruptive degassing of rising magmas, improving
prediction of volcanic activity
Prediction of volcanic activity, and volcanic eruption forecasting, is an interdisciplinary monitoring and research effort to predict the time and severity of a volcano's eruption. Of particular importance is the prediction of hazardous eruptions ...
.
There is also another mountain called Asama (朝熊山, ''Asama-yama'') of only 555 meters in
Mie Prefecture
is a Prefectures of Japan, prefecture of Japan located in the Kansai region of Honshu. Mie Prefecture has a population of 1,781,948 () and has a geographic area of . Mie Prefecture is bordered by Gifu Prefecture to the north, Shiga Prefecture an ...
.
Eruptive history
The geologic features of this active volcano are closely monitored with
seismograph
A seismometer is an instrument that responds to ground displacement and shaking such as caused by quakes, volcanic eruptions, and explosions. They are usually combined with a timing device and a recording device to form a seismograph. The out ...
s and strategically positioned video cameras.
[ VolcanoLive.com](_blank)
/ref> Scientists have noted a range of textural variety in the ash which has been deposited in the region during the serial eruptions since the ''Tennin'' eruption of 1108.
''Tennin'' eruption (1108)
The eruption of Mount Asama in 1108 (''Tennin
, which may include , , and the specifically female version, the , are a divine kind of spiritual beings found in Japanese Buddhism, the equivalent of angels. They were seemingly imported from Chinese Buddhism, which was itself influenced by ...
1'') has been the subject of studies by modern science. Records suggest that the magnitude of this plinian eruption was twice as large as that of the ''Tenmei'' catastrophe in 1783.
A Swiss research team found Mount Asama's volcanic eruption could have contributed to extreme weather that caused severe famine, torrential rain and consecutive cold summers in Europe. They studied ice cores in Greenland
Greenland is an autonomous territory in the Danish Realm, Kingdom of Denmark. It is by far the largest geographically of three constituent parts of the kingdom; the other two are metropolitan Denmark and the Faroe Islands. Citizens of Greenlan ...
which had increased sulfate deposition in 1108 CE. In the late Heian Period
The is the last division of classical Japanese history, running from 794 to 1185. It followed the Nara period, beginning when the 50th emperor, Emperor Kammu, moved the capital of Japan to Heian-kyō (modern Kyoto). means in Japanese. It is a ...
(794–1185) the diary of the court noble Fujiwara no Munetada reported that Mount Asama erupted on 29 August 1108. He wrote that a local report described rice paddies and fields could not be farmed due to being covered by a thick layer of ash.
''Tenmei'' eruption (1783)
Mount Asama erupted in 1783 (''Tenmei
is a Japanese era name (年号, ''nengō'', literally "years name") for the years between the An'ei Era and before the Kansei Era, from April 1781 through January 1789. The reigning emperor was .
Change of era
* 1781 : The new era name of Ten ...
3''), causing widespread damage. The three-month-long 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 that began on 9 May 1783, produced andesitic
Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predomina ...
pumice falls, pyroclastic
Pyroclast, Pyroclastic or Pyroclastics may refer to:
Geology
* Pyroclast, or airborne volcanic tephra fragments
* Pyroclastic rock, rock fragments produced and ejected by explosive volcanic eruptions
* Pyroclastic cone, landform of ejecta fro ...
flows, lava flows, and enlarged the cone. The climactic eruption began on 4 August and lasted for 15 hours, and contained pumice falls and pyroclastic flows. The complex features of this eruption are explained by rapid deposits of coarse pyroclastic ash near the vent and the subsequent flows of lava; and these events which were accompanied by a high eruption plume
An eruption column or eruption plume is a cloud of super-heated ash and tephra suspended in gases emitted during an explosive volcanic eruption. The volcanic materials form a vertical column or plume that may rise many kilometers into the air ...
which generated further injections of pumice into the air.
1982 eruption
Explosive eruptions occurred at the summit of Asama volcano on 26 April. Fine ash fell in Tokyo, to the SE, for the first time in 23 years.
1983 eruptions
An explosive eruption occurred on 8 April. Incandescent tephra was ejected, and ash fell from the volcano.
1995 earthquakes
In April 1995, more than 1000 earthquakes were detected at the volcanic mountain.
2004 eruption
A single vulcanian eruption occurred at Asama volcano at 11:02 UT on 1 September 2004. Incandescent blocks were ejected from the summit and caused many fires. The eruption sent ash and rock as far away as .
2008 eruptions
Three small ash eruptions occurred at Asama volcano in August 2008. This was the first activity at the volcano since 2004.
2009 eruptions
Mount Asama erupted in early February 2009, sending ash to a height of ,["Volcano erupts close to Tokyo,"](_blank)
BBC. 2 February 2009. and throwing rocks up to from the crater. Ash fall was reported in Tokyo, southeast of the volcano crater. On 16 February there were 13 recorded volcanic earthquakes and an eruption emitting smoke and ash in a cloud high.
Mount Asama continued to have small eruptions, tremors and earthquakes in February and remained on level-3 alert, with a danger zone within of the crater.
18 February 2009.
2019 eruption
A small eruption occurred on August 7th, 2019, with smoke reaching about 1,800 meters above the mountain.
Marking the span of Japan's history
The eruptions of Mount Asama mark the span of Japan's recorded history, including: 2019, ''2009'', ''2008'', ''2004'', 2003, ''1995'', 1990, ''1983'', ''1982'', 1973, 1965, 1961, 1958–59, 1953–55, 1952, 1952, 1950–51, 1949, 1947, 1946, 1944–45, 1938–42, 1935–37, 1934, 1934, 1933, 1931–32, 1930, 1929, 1929, 1927–28, 1924, 1922, 1920–21, 1919, 1918?, 1917, 1916, 1915, 1914, 1909–14, 1908, 1908, 1907, 1907, 1906, 1905?, 1904, 1903, 1902, 1902, 1900–01, 1899, 1899, 1894, 1889, 1879, 1878?, 1875, 1869, 1815, 1803, 1803, ''1783'', 1779?, 1777, 1776, 1769, 1762, 1755, 1754, 1733, 1732, 1731, 1729, 1729, 1728, 1723, 1723, 1722, 1721, 1720, 1719, 1718, 1717, 1711, 1710, 1708–09, 1706, 1704, 1703, 1669, 1661, 1661, 1660, 1659, 1658, 1657, 1656, 1655, 1653, 1652, 1651, 1650?, 1649, 1648, 1648, 1647, 1645, 1644, 1609, 1605, 1604, 1600, 1598, 1597, 1596, 1596, 1595?, 1591, 1590, 1532, 1528, 1527, 1518, 1427?, 1281, ''1108'', 887, 685.
Note: The dates of eruptions featured in this article appear in bold italics.
Onioshidashi
Onioshidashi () "expelling demons" is the name of a lava flow
Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...
on the northern slope of Mount Asama. The lava flow that erupted in 1783 Tenmei eruption
The was a large eruption of Mount Asama that occurred in 1783 (''Tenmei 3''). This eruption was one of the causes of the Tenmei famine. It is estimated that about 1,500–1,624 people were killed in the eruption. The event is known in Japanese ...
was solidified. Now, it is known as a tourist destination.
Asama Volcano Museum
The Asama Volcano Museum (), from the crater of the Mount Asama,[浅間火山博物館閉館へ](_blank)
『読売新聞』(''Yomiuri Shimbun
The is a Japanese newspaper published in Tokyo, Osaka, Fukuoka, Fukuoka, Fukuoka, and other major Japanese cities. It is one of the five major newspapers in Japan; the other four are ''The Asahi Shimbun'', the ''Chunichi Shimbun'', the ''Ma ...
''), 8 August 2020. Accessed 1 July 2021. open from 1993 to 2020, explained volcanoes.
The museum was in Naganohara-machi, Agatsuma-gun, Gunma Prefecture
is a landlocked Prefectures of Japan, prefecture of Japan located in the Kantō region of Honshu. Gunma Prefecture has a population of 1,937,626 (1 October 2019) and has a geographic area of . Gunma Prefecture borders Niigata Prefecture and Fuk ...
. As of early 2009, it was open from April until November.
Visitor numbers peaked at 265,000 in 1994; however, seismic activity at nearby Mount Asama was one reason for frequent closures. The closures were a factor in the drop in visitors:[浅間火山博物館を閉館 年度内に長野原町 新型コロナで休館中](_blank)
『上毛新聞』 ('' Jōmō Shinbun''), 9 August 2020. Accessed 1 July 2021. this gradually fell to 23,000. In the later years of the museum, most of the visitors were on school excursions. The museum was running a deficit of about 17 million yen per year, paid for by the town of Naganohara. Additionally, the building was ageing, and maintenance threatened to cost hundreds of millions of yen.
A nearby building, Asama memorial hall () exhibited motorbikes; the plan in summer 2020 was to move these to a municipally owned tourist facility, Asama pasture (), and to move some of the exhibits of the volcano museum to the memorial hall.
Gallery
File:Mt.Asama2 (From saku city).jpg, Viewed from the south
File:220929 Mt Asama Karuizawa Nagano pref Japan01s3.jpg, Viewed from the southeast
File:Mt asama.jpg, Viewed from the SSE
File:Mt.Asama (From onioshidashi).jpg, Viewed from the north
File:Kisokaido03 Urawa.jpg, Hiroshige
or , born Andō Tokutarō (; 1797 – 12 October 1858), was a Japanese ''ukiyo-e'' artist, considered the last great master of that tradition.
Hiroshige is best known for his horizontal-format landscape series '' The Fifty-three Stations ...
In popular culture
Mount Asama served as the backdrop to Japan's first colour film, ''Carmen Comes Home
is a 1951 Japanese comedy film directed by Keisuke Kinoshita. It was Japan's first feature length colour film.
Plot
Due to the renovation of the Tokyo based venue where she works, Okin, stage name Lily Carmen, and her lovesick friend Maya pay h ...
''. Several references are made to Mount Asama throughout the film, including a melody composed by a blind composer, Mr. Taguchi.
In the anime ''Neon Genesis Evangelion
, also known as ''Evangelion'' or ''Eva'', is a Japanese mecha anime television series produced by Gainax and Tatsunoko Production, and directed by Hideaki Anno. It was broadcast on TV Tokyo and its affiliates from October 1995 to March 1 ...
'', the Eighth Angel, Sandalphon, was located inside Mount Asama.
See also
*Tenmei eruption
The was a large eruption of Mount Asama that occurred in 1783 (''Tenmei 3''). This eruption was one of the causes of the Tenmei famine. It is estimated that about 1,500–1,624 people were killed in the eruption. The event is known in Japanese ...
Notes
References
* Hall, John Whitney (1955). '' Tanuma Okitsugu
(September 11, 1719 – August 25, 1788) was a chamberlain (''sobashū'') and a senior counselor ('' rōjū'') to the ''shōgun'' Tokugawa Ieharu of the Tokugawa Shogunate, in the Edo period of Japan. Tanuma and his son exercised tremendo ...
, 1719–1788: Forerunner of Modern Japan, '' Cambridge: Harvard University Press
Harvard University Press (HUP) is an academic publishing house established on January 13, 1913, as a division of Harvard University. It is a member of the Association of University Presses. Its director since 2017 is George Andreou.
The pres ...
.
*Hayakawa, Yukio and Hideko Nakajima
"Volcanic Eruptions and Hazards of Asama Written in Historical Records" (abstract)
''Bulletin of the Volcanological Society of Japan'' (''Kazan
Kazan; , IPA: Help:IPA/Tatar, ɑzanis the largest city and capital city, capital of Tatarstan, Russia. The city lies at the confluence of the Volga and the Kazanka (river), Kazanka Rivers, covering an area of , with a population of over 1. ...
''). 19 July 2006.
* Screech, Timon (2006)
''Secret Memoirs of the Shoguns: Isaac Titsingh and Japan, 1779–1822.''
London: RoutledgeCurzon
Routledge ( ) is a British multinational publisher. It was founded in 1836 by George Routledge, and specialises in providing academic books, journals and online resources in the fields of the humanities, behavioural science, education, law, a ...
. (cloth); (electronic)
* Titsingh, Isaac (1834). iyun-sai Rin-siyo/Hayashi Gahō, 1652">Hayashi_Gahō.html" ;"title="iyun-sai Rin-siyo/iyun-sai Rin-siyo/Hayashi Gahō, 1652 ''Nipon o daï itsi ran">Hayashi Gahō">iyun-sai Rin-siyo/Hayashi Gahō, 1652">Hayashi_Gahō.html" ;"title="iyun-sai Rin-siyo/Hayashi Gahō">iyun-sai Rin-siyo/Hayashi Gahō, 1652 ''Nipon o daï itsi ran; ou
Annales des empereurs du Japon.' Paris: Royal Asiatic Society">Oriental Translation Fund of Great Britain and Ireland
The Royal Asiatic Society of Great Britain and Ireland, commonly known as the Royal Asiatic Society, was established, according to its royal charter of 11 August 1824, to further "the investigation of subjects connected with and for the encourag ...
.
External links
Asamayama
– Japan Meteorological Agency
* – Japan Meteorological Agency
– Geological Survey of Japan
Asamayama
– Smithsonian Institution: Global Volcanism Program
{{DEFAULTSORT:Asama
Mountains of Gunma Prefecture
Mountains of Nagano Prefecture
Volcanoes of Honshū
Subduction volcanoes
Active volcanoes
VEI-5 volcanoes
Complex volcanoes
18th-century volcanic events
Volcanoes of Gunma Prefecture
Volcanoes of Nagano Prefecture
Highest points of Japanese national parks
Calderas of Honshū