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 is an active complex volcano in central HonshŇęmarker, the main island of Japanmarker. The volcano is the most active on HonshŇę. The Japan Meteorological Agency classifies Mount Asama as rank A. It stands   above sea level on the border of Gunmamarker and Nagano prefecturesmarker. It is one of the 100 famous mountains in Japan.


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

Scientists from Tokyo Universitymarker 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.

The eastern slope has a volcano observation station run by Tokyo Universitymarker.

Eruptive history

The geologic features of this active volcano are closely monitored with seismographs and strategically positioned videos cameras. 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.

2009 eruptions

Mount Asama erupted in early February 2009, sending ash to a height of 2 km, and throwing rocks up to 1 km from the crater. Ashfall was reported in Tokyo, 145 km southeast of the volcano crater. On February 16th there were 13 recorded volcanic earthquakes and an eruption emitting smoke and ash in a cloud 400 m high.

Mount Asama has continued to have small eruptions, tremors and earthquakes in February and has remained on level 3 alert (danger zone is within 4 km of the crater).

2008 eruptions

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

2004 eruption

A single vulcanian eruption occurred at Asama volcano at 11:02 UT on 1st September 2004. Incandescent blocks were ejected from the summit and caused many fires.The eruption sent ash and rock as far away as .

1995 earthquakes

In April 1995, more than 1000 earthquakes were detected at the volcano.

1983 eruptions

An explosive eruption occurred on 8th April. Incandescent tephra was ejected, and ash fell 250 km from the volcano.

1982 eruption

Explosive eruptions occurred at the summit of asama volcano on 26th April. Fine ash fell in Tokyo, 130 km to the SE, for the first time in 23 years.

Tenmei eruption

Mount Asama erupted in 1783 (Tenmei 3), causing widespread damage. The 3-month-long plinian eruption in 1783 produced andesitic pumice falls, pyroclastic flows, lava flows, and enlarged the cone. The climactic eruption lasted for 15 hours; and there was pumice fall 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 which generated further injections of pumice into the air.

Isaac Titsingh's account of the Asama-yama eruption was posthumously published in French in Paris in 1820; and an English translation was published in London in 1822. These books were based on Japanese sources; and the work represented first of its kind to be disseminated in Europe and the West.

The volcano's devastation exacerbated what was already known as the "Great Tenmei Famine." Much of the agriculturally productive land in Shinano and KŇćzuke provinces would remain fallow or under-producing for the next four or five years. The effects of this eruption were made worse because, after years of near or actual famine, neither the authorities nor the people had any remaining reserves.

Tennin eruption

The eruption of Mount Asama in 1108 (Tennin 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.

Marking the span of Japan's history

The eruptions of Mount Asama mark the span of Japan's recorded history, including: 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.


  2. Asama
  3. 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.
  4. "Volcano erupts close to Tokyo," BBC. February 2, 2009.
  5. [1] February 18, 2009.
  6. Titsingh, Isaac. (1834). Annales des empereurs du japon, p. 420.
  7. 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.
  8. Titsingh, Isaac. (1820). Mémoires et Anecdotes sur la Dynastie régnante des Djogouns, Souverains du Japon.
  9. Titisngh, Isaac. (1822). Illustrations of Japan: consisting of private memoirs and anecdotes of the reigning dynasty of the Djogouns, or sovereigns of Japan.
  10. Screech, T. (2006), Secret Memoirs of the Shoguns: Isaac Titsingh and Japan, 1779-1822, pp. 146-148.
  11. Hall, John. (1955). Tanuma Okitsugu, 1719-1788: Forerunner of Modern Japan, p. 122.
  12. Hall, p. 170.
  13. Centre national de la recherche scientifique (CNRS), 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.
  14. Hayakawa, Yukio and Hideko Nakajima. "Volcanic Eruptions and Hazards of Asama Written in Historical Records" (abstract), Bulletin of the Volcanological Society of Japan (Kazan). July 19, 2006.
  15. Note: The dates of eruptions featured in this article appear in bold italics.



Image:Asama-yama.JPG|Mount AsamaImage:AsamaYama.JPG|Mount Asama December 2005Image:AsamaYama2.JPG|Mount Asama December 2005 from Gunma PrefectureImage:IMG Mt.Asama.JPG|Mount Asama from Nagano Prefecture in 1999Image:Mt asama.jpg|View from the train near Ueda city in 2005Image:Mt-asama01.JPG|Taken from Tateshina, Nagano Prefecture

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