Abstract
The eruption clouds by the strong fissure eruptions on November 21, 1986 at Izu-Oshima volcano, Izu Islands, Japan are well detected in GMS imageries. The top altitude of eruption clouds estimated from the coldest surface temperature of GMS infrared data is 7-9 km, but this value is distinctly lower than the reliable heights of 10-16 km determined by the observations from the ground and weather radars. The northern edge of the extent of eruption cloud in GMS imagery is apparently over the southern tip of the Boso Peninsula. These two apparent observation results can be corrected with considerations of the effect of the GMS's parallax angle. The reason of the underestimation of the top altitude may be due to heat discharges through the surface of eruption cloud from internal heat source during the development of eruption clouds.
