At July 8,1991, some blocks of 2nd lava dome were break and rolling down on the slope. Then these rocks crash with hard rock on valley wall and explosion (burst) was occurred and a small pyroclastic flow happened. That reason of this type explosion was lead high gas pressure inside of a rock. [
Sato,H.et al.ªFNature, 360, 664-666 (1992). ]
Fig-1 Photos of just explosion by small rock fall.
These photos were taken by Tatsuro CHIBA with 200mm lens from Fukae town at 11:02 on July 8, 1991.
Fig-2 Animation of just explosion by small rock fall.
This animation was made by GifBuilder ver.0.3.2.(4/30/96).