Historic eruptions of Mount Fuji

Mount Fuji is the tallest volcano in Japan, and also the volcano with the greatest volume. It is believed to have grown greatly in volume in the last 100,000 years, so it can be classified as a "young volcano".

The mountain as it appears now is the "New Fuji volcano", which began to erupt about 10,000 years ago. Under the "New Fuji volcano" lie the "Komitake volcano", which became active 700,000 years ago, and the "Old Fuji volcano", which was active between 100,000 years ago and 1000 years ago.

Komitake

There has been much volcanic activity in the vicinity of Mount Fuji for several million years. 700,000 years ago, in the location occupied by the current Mount Fuji, a volcano known as nihongo|Mount Komitake|小御岳火山, literally meaning "small mountain volcano", became active. Around this time, another volcano, nihongo|Mount Ashitaka|愛鷹山, in the area to the south-east of Mount Fuji, was also highly active.The peak of the ancient volcano, Komitake, can be seen from the north face of Mount Fuji at the fifth station, about 2300 meters above sea-level.

Old Fuji

Around 100,000 years after becoming inactive, Komitake entered another period of activity. The volcano in this period is known as nihongo|Old Fuji|古富士|kofuji. Old Fuji was characterised by explosive eruptions, throwing out large quantities of scoria, volcanic ash and lava, forming a large mountain which reached a height of 3,000m.

New Fuji

Following the Old Fuji period, there were about 4000 years of inactivity, ending at around 5000 years ago, when Mount Fuji became active again; this period is known as nihongo|New Fuji|新富士|shinfuji, and continues to the present day. Eruptions of New Fuji exhibit phenomena such as lava flows, magma, scoria, volcanic ash, collapses and side eruptions, leading it to be called "a department store of eruptions". Ash from New Fuji is often black, and eruptions are new in terms of geological layers. Valuable data on the activity of Mount Fuji is recorded in Japanese historical documents dating from the 8th century onwards. It exhibits a range of representative eruptions.

Explosive eruptions before the activity 3000 years ago

There were 4 explosive eruptions in the Jōmon era, which are known by the names Sengoku scoria (Sg), Ōsawa scoria (Os), Ōmuro scoria (Om) and Sunazawa scoria (Zn). As the wind normally blows from the west in the area of Mount Fuji, most ejectants fall to the east, but in the case of the Ōsawa scoria, they were carried on the east wind, as far as the vicinity of Hamamatsu.There are also 15-16 total eruptions of Mt. Fuji

The Gotemba mud flow

About 2300 years ago the east face of the volcano collapsed and liquid mud flowed down to the Gotemba area as far as the Ashigara plain in the east and the Suruga bay across Mishima city in the south. This incident is now called the nihongo|Gotemba mud flow|御殿場泥流|Gotemba deiryū. Liquid mud piled up over an area as wide as the city area of Mishima.

Jōgan eruption

In 864 (the 6th year of the "Jōgan" era) there was an eruption on the north-east side of Mount Fuji, which produced a great amount of lava.
* 864 ("Jōgan 6, 5th month"): Mount Fuji erupted during 10 days, and it ejected from its summit an immense quantity of cinders and ash which fell back to earth as far away as the ocean at Edo bay. Many people perished and a great number of homes were destroyed. The volcanic eruption began on the side of Fuji-san closest to Mount Asama, throwing cinders and ash as far away as Kai province. [Titsingh, Isaac. (1834). [http://books.google.com/books?id=18oNAAAAIAAJ&pg=PP9&dq=nipon+o+dai+itsi+ran#PRA1-PA118,M1 "Annales des empereurs du japon," p. 118.] ] Some of the lava filled up a large lake nihongo|Senoumi|せの海 which existed at the time, dividing it into two lakes, nihongo|Saiko|西湖 and nihongo|Shōjiko|精進湖. This is known as the nihongo|Aokigahara lava|青木ヶ原溶岩, and at present is covered by the dense Aokigahara forest.

Hōei eruption

The latest eruption, in 1707 (the 4th year of the "Hōei" era), was known as the great "Hōei" eruption. It followed several weeks after the Great "Hōei" earthquake:
* November 11, 1707 ("Hōei 4, 14th day of the 10th month"): The city of Osaka suffers tremendously because of a very violent earthquake. [Titsingh, [http://books.google.com/books?id=Cg8oAAAAMAAJ&printsec=titlepage&dq=editions:OCLC63259938#PRA1-PA415,M1 p. 415.] ]
* December 16, 1707 ("Hōei 4, 23nd day of the 11th month"): An eruption of Mt. Fuji; the cinders and ash fell like rain in Izu, Kai, Sagami, and Musashi. [ [http://sk01.ed.shizuoka.ac.jp/koyama/public_html/Fuji/fujid/1707.html Shikuoka University page;] "see" Japanese Wikipedia.] This eruption was remarkable in that spread a vast amount of volcanic ash and scoria over a region as far away as Edo.

Records of eruption

16 eruptions of New Fuji have been recorded since 781. Many of the eruptions occurred in the Heian era, with 12 eruptions between 800 and 1083. Sometimes inactive periods between eruptions lasted for hundreds of years, as in the period between 1083 and 1511, when no eruptions were recorded for over 400 years. At present, there have been no eruptions since the Hoei eruption in 1707-1708, around 300 years ago.

See also

* Mount Fuji
* Hoei eruption of Mount Fuji

References

*, "Mount Fuji - All About Its Nature", written by nihongo|Akira Suwa|諏訪彰 1992 nihongo|Dōbunshoin|同文書院 ISBN 4-8103-4047-3
* Titsingh, Isaac. (1834). [Siyun-sai Rin-siyo/Hayashi Gahō, 1652] , "Nipon o daï itsi ran; ou, Annales des empereurs du Japon, tr. par M. Isaac Titsingh avec l'aide de plusieurs interprètes attachés au comptoir hollandais de Nangasaki; ouvrage re., complété et cor. sur l'original japonais-chinois, accompagné de notes et précédé d'un Aperçu d'histoire mythologique du Japon, par M. J. Klaproth." Paris: Oriental Translation Fund of Great Britain and Ireland. [http://books.google.com/books?id=18oNAAAAIAAJ&dq=nipon+o+dai+itsi+ran ... Click link for digitized, full-text copy of this book (in French)]