Heat from the high lava lake
level in the 'overlook' vent
in Halema‘uma‘u is causing the walls of the vent above the lava
surface to expand and fracture. This is the source of the cracking and booming noises emanating from the vent in recent days. This video, zoomed in on the back (NW) wall of the vent, shows small fragments of rock exploding from the wall and scattering onto the lake surface. Watch closely...the rocks are originating from an alcove that overhangs the lake and can be difficult to see.