Keywords:Kusatsu-Shirane volcano, steam eruption, crater row
A steam explosion of Kusatsu-Shirane Volcano on January 23, 2018, occurred at Northern end of summit crater of Moto-Shirane Volcano that had no record of eruption in historical time. (Recent eruptions have occurred in Shirane Volcano famous for its blue crater lake, that is located 2 km north of Moto-Shirane.) The new crater row (up to 500m long) is aligned in WNW-ESE direction, that is nearly normal to the main alignment of pyroclastic volcanic bodies in Kusatsu-Shirane Volcano. The bi-axial two directions may represent the main stress field from E in this volcano area.
Video images of the new eruption shows specific characters of steam explosion with fallen blocks, lapilli, and ash without heat. In February the new small craters are covered by snow, and no one can reach there. However, there may still be a danger of leak of poisonous gas.