Rockfall generates a short-lived explosion at Halema‘uma‘u crater, at 8:27 a.m. HST, May 9.
An ash column rises from the Overlook crater at the summit of Kīlauea Volcano today. The USGS-Hawaiian Volcano Observatory’s interpretation is that the explosion was triggered by a rockfall from the steep walls of Overlook crater.
The summit lava lake level has dropped about 220 m (722 ft) below the crater rim from April 30-May 7. The water table is about 460m (1970 ft) below the caldera floor. This explosion was due to a rockfall and not the interaction of magma with the water table.
This photograph was taken at 8:29 a.m. HST on May 9, from the Jaggar Museum overlook. The explosion was short-lived. Geologists examining the ash deposits on the rim of Halema‘uma‘u crater found fresh lava fragments hurled from the lava lake. This explosion was not caused by the interaction of the lava lake with the water table. When the ash cleared from the crater about an hour after the explosion, geologists were able to observe the lava lake surface, which is still above the water table.