Mount Asama

Mount Asama (浅間山, Asama-yama) is an active complex volcano in central Honshū, the main island of Japan. The volcano is the most active on Honshū.[3] The Japan Meteorological Agency classifies Mount Asama as rank A.[4] It stands 2,568 metres (8,425 ft) above sea level on the border of Gunma and Nagano prefectures.[5] It is included in 100 Famous Japanese Mountains.

Mount Asama
Viewed from the East
Highest point
Elevation2,568 m (8,425 ft)
ListingList of mountains and hills of Japan by height
100 famous mountains in Japan
List of volcanoes in Japan
Coordinates36°24′23″N 138°31′23″E[1]
Native name浅間山 (Japanese)
Mount Asama
Honshū, Japan
Mount Asama
Mount Asama (Gunma Prefecture)
Topo mapGeographical Survey Institute 25000:1 浅間山
50000:1 長野
Age of rockLate PleistoceneHolocene[2]
Mountain typeComplex volcano
Last eruption7 August 2019


Mount Asama sits at the conjunction of the Izu–Bonin–Mariana Arc and the Northeastern Japan Arc.[3] The mountain is built up from non-alkali mafic and pyroclastic volcanic rocks dating from the Late Pleistocene to the Holocene.[2] The main rock type is andesite and dacite.[6]

Viewed from the north

Scientists from the University of Tokyo and Nagoya University completed their first successful imaging experiment of the interior of the volcano in April 2007. By detecting sub-atomic particles called muons 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.[7]

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, which detects pre-eruptive degassing of rising magmas, improving prediction of volcanic activity.[8]

There is also another mountain called Asama (朝熊山, Asama-yama) of only 555 meters in Mie Prefecture.[9]

Eruptive history

Relief map

The geologic features of this active volcano are closely monitored with seismographs and strategically positioned video cameras.[10] 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.[11]

Tennin eruption (1108)

The eruption of Mount Asama in 1108 (Tennin 1) has been the subject of studies by modern science.[12] Records suggest that the magnitude of this plinian eruption was twice as large as that of the Tenmei catastrophe in 1783.[13]

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 which had increased sulfate deposition in 1108 CE. In the late Heian Period (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.[14]

Tenmei eruption (1783)

Mount Asama erupted in 1783 (Tenmei 3), causing widespread damage.[15] The three-month-long plinian eruption that began on 9 May 1783, produced andesitic pumice falls, pyroclastic flows, lava flows, and enlarged the cone. The climactic eruption began on 4 August and lasted for 15 hours,[16] and contained pumice falls and pyroclastic flows.[10] 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 which generated further injections of pumice into the air.[17]

1982 eruption

Explosive eruptions occurred at the summit of Asama volcano on 26 April. Fine ash fell in Tokyo, 130 km (80 mi) to the SE, for the first time in 23 years.[10]

1983 eruptions

An explosive eruption occurred on 8 April. Incandescent tephra was ejected, and ash fell 250 km (160 mi) from the volcano.[10]

1995 earthquakes

In April 1995, more than 1000 earthquakes were detected at the volcanic mountain.[10]

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.[10] The eruption sent ash and rock as far away as 200 km (120 mi).[18]

2008 eruptions

Three small ash eruptions occurred at Asama volcano in August 2008. This was the first activity at the volcano since 2004.[10]

2009 eruptions

Mount Asama erupted in early February 2009, sending ash to a height of 2 km (6,600 ft),[18] and throwing rocks up to 1 km (⅝ mi) from the crater. Ash fall was reported in Tokyo, 145 km (90 mi) southeast of the volcano crater. On 16 February there were 13 recorded volcanic earthquakes and an eruption emitting smoke and ash in a cloud 400 m (1,300 ft) high.

Mount Asama continued to have small eruptions, tremors and earthquakes in February and remained on level-3 alert (with a danger zone within 4 km (2½ mi) of the crater).[19]

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.[10]

Note: The dates of eruptions featured in this article appear in bold italics.


Map of Onioshidashi lava flow
Onioshidashi lava flow on the southern foot (erupted in 1783)

The Onioshidashi (Japanese: 鬼押出し) is the name of lava flow on the northern slope of Mount Asama.[20] The lava flow that erupted in 1783 Tenmei eruption was solidified.[21] Now, it is known as a tourist destination.[22]

Asama Volcano Museum

Asama Volcano Museum

The Asama Volcano Museum (浅間火山博物館), 4 km (2.5 mi) from the crater of the Mount Asama,[23] open from 1993 to 2020, explained volcanoes.

The museum was in Naganohara-machi, Agatsuma-gun, Gunma Prefecture. 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:[24] this gradually fell to 23,000.[23] In the later years of the museum, most of the visitors were on school excursions.[24] 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.[23][24]

A nearby building, Asama memorial hall (浅間記念館) exhibited motorbikes; the plan in summer 2020 was to move these to a municipally owned tourist facility, Asama pasture (浅間牧場), and to move some of the exhibits of the volcano museum to the memorial hall.[23]

Mount Asama served as the backdrop to Japan's first colour film, Carmen Comes Home.[25] 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, the Eighth Angel, Sandalphon, was located inside Mount Asama.[26]

See also

  • Tenmei eruption


  1. "浅間山" (in Japanese). 気象庁. Retrieved 23 May 2022.
  2. "Hokuriku". Seamless Digital Geological Map of Japan. Geological Survey of Japan, AIST. 2007. Archived from the original on 6 February 2009. Retrieved 2 February 2009.
  3. "Asama". Global Volcanism Program. Smithsonian Institution. Retrieved 2 February 2009.
  4. "List of Active Volcanoes in Japan". Quaternary Volcanoes in Japan. Geological Survey of Japan, AIST. 2006. Archived from the original on 9 December 2012. Retrieved 3 February 2009.
  5. "浅間山とは". Kotobank (in Japanese). Retrieved 23 May 2022.
  6. "ASAMA-YAMA". Quaternary Volcanoes in Japan. Geological Survey of Japan, AIST. 2006. Archived from the original on 19 December 2012. Retrieved 3 February 2009.
  7. Tanaka, Hiroyuki K. M.; Nakano, Toshiyuki; Takahashi, Satoru; Yoshida, Jyunya; Takeo, Minoru; Oikawa, Jun; Ohminato, Takao; Aoki, Yosuke; Koyama, Etsuro; Tsuji, Hiroshi; Niwa, Kimio (2007). "High resolution imaging in the inhomogeneous crust with cosmic-ray muon radiography: The density structure below the volcanic crater floor of Mt. Asama, Japan". Earth and Planetary Science Letters. 263 (1–2): 104. Bibcode:2007E&PSL.263..104T. doi:10.1016/j.epsl.2007.09.001.{{cite journal}}: CS1 maint: uses authors parameter (link)
  8. "Real-Time Multi-GAS sensing of volcanic gas composition: experiences from the permanent Etna and Stromboli networks, Geophysical Research Abstracts, Vol. 11, EGU2009-5839" (PDF).
  9. Bastion, Arlene. "Huffing and Puffing Up Mt Asama". Japan Travel. Retrieved 13 April 2022.
  10. Asama
  11. Yasui, Maya, Takahashi Masaki, and Sakagami Masakuki. "Textural Variety in the Eruptive Products of Vulcanian Eruptions between 1108 A.D. and 2004 A.D. on Asama-Maekake Volcano," Bulletin of the Volcanological Society of Japan (Kazan). Vol. 50, No. 6 (2005). pp. 501–517.
  12. Centre national de la recherche scientifique (CNRS) Archived 25 February 2009 at the Wayback Machine, France: Yoshida, Minoru and Aoyagi, Ryugi. "Fluorine and chlorine contents in the products of the 1108 (Tennin) eruption of Asama volcano," Bulletin of the Volcanological Society of Japan (Kazan). Vol. 49, No. 4 (2004). pp. 189–199.
  13. Hayakawa, Yukio and Hideko Nakajima. "Volcanic Eruptions and Hazards of Asama Written in Historical Records" (abstract), Bulletin of the Volcanological Society of Japan (Kazan). 19 July 2006.
  14. Yu Fujinami (2020). "Mt. Asamayama eruption in 1108 may have led to famine in Europe". Asahi. Archived from the original on 21 June 2020. Retrieved 20 June 2020.
  15. Titsingh, Isaac. (1834). Annales des empereurs du japon, p. 420.
  16. Richards, John F. (2003). The Unending Frontier: An Environmental History of the Early Modern World. University of California Press. p. 177. ISBN 9780520939356. Retrieved 2 August 2013.
  17. Yasui, Maya and Takehiro Koyaguchi. "Sequence and eruptive style of the 1783 eruption of Asama Volcano, central Japan: a case study of an andesitic explosive eruption generating fountain-fed lava flow, pumice fall, scoria flow and forming a cone," Journal Bulletin of Volcanology (Kasan). Vol. 66, No. 3 (March 2004). pp. 243–262.
  18. "Volcano erupts close to Tokyo," BBC. 2 February 2009.
  19. Archived 21 February 2009 at the Wayback Machine 18 February 2009.
  20. "鬼押出とは". Kotobank (in Japanese). Retrieved 22 May 2022.
  21. "鬼押出しとは". Kotobank (in Japanese). Retrieved 22 May 2022.
  22. "鬼押出岩とは". Kotobank (in Japanese). Retrieved 22 May 2022.
  23. 浅間火山博物館閉館へ, 『読売新聞』(Yomiuri Shinbun), 8 August 2020. Accessed 1 July 2021.
  24. 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, 『上毛新聞』 (Jōmō Shinbun), 9 August 2020. Accessed 1 July 2021.
  25. "Notes on the Cinema Stylographer: Carmen Comes Home, 1951". Archived from the original on 12 October 2016. Retrieved 15 January 2017.
  26. Fujie, Kazuhisa; Foster, Martin (2004). Neon Genesis Evangelion: The Unofficial Guide. DH Publishing Inc. p. 176. ISBN 978-0-9745961-4-3.


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