Introduction Japan has 86 active volcanoes according to definition of Meteorological Agency of Japan.
Volcanic disasters are very serious problem for our country.
The 1990-95 eruption of Unzen volcano reminds in the memory of people. The eruption killed 44 persons and devastated extensively the surrounding of the volcano. We examined the deposits and forest damages associated with the Unzen eruption. The activity commenced with a phreatic eruption in November 1990 and shifted to magmatic eruption characterized by lava dome growth and pyroclastic flows in May 1991. A dacite lava dome appeared in a summit crater and grew unstably.