Mount Asama

Asama in 2005

The Asama (Japanese浅 间 山, -yama ) is a complex volcano on the Japanese island of Honshu. It is located approximately 150 kilometers northwest of Tokyo on the border of Gunma prefecture and Nagano. The Asama is the most active volcano on the island of Honshu.

Construction

The Asama is located slightly east of the Kurofu, a volcano composed of andesite, which was destroyed around 20,000 years ago by a landslide. Then, a shield volcano from dacite originated; He was the starting point of pyroclastic flows in particular 11000-14000 years ago. At the same time the lava dome Ko - Asama, located about three miles east of the present-day summit was. All eruptions in historical times went out from Maekake, which probably has an age of a few thousand years. Placed the Maekake is the coma, a pyroclastic cone with a height of 2568 meters, the summit of the volcano.

Outbreaks

From a historical time numerous outbreaks are known; to particularly strong eruptions occurred in the years 1108 and 1783.

At the outbreak from May to August 1783 came to Plinian eruptions and vulcanian; in the latter pumice was promoted. In addition, lava flowed from and were formed pyroclastic flows. At the outbreak around 1500 people died, in part by the pyroclastic flows, in part by flooding, were the result of the eruption. The ejected dust and ash quantities reduced the sunlight, making the weather was cold and rainy. Between 1783 and 1787 there was a famine in northern Japan, where an estimated 300,000 people died. The eruption of Asama is known as one of several causes of the famine. On the exceptionally cold winter of 1783 /84, the eruption of Asama compared to 1783 also broken Laki craters in Iceland had only a slight influence.

The last eruptions of Asama were in the years 2004, 2008 and 2009. Between September and November 2004, there were several explosive eruptions in which ash was ejected. In the crater was formed a new lava dome temporarily.

Since 1933, the University of Tokyo operates a volcano observatory at Asama, located in approximately 1,400 meters above sea level on the eastern slope. The Observatory was the first of its kind in Japan and was instrumental in the development of volcanology in Japan. In particular, earthquakes have been explored that precede volcanic eruptions frequently.