Lava within the Halema`uma`u vent cavity

movie shows lava within the Halema`uma`u vent cavity, at a depth of about 200 m below the vent rim. The lava surface, which is about 20 m wide, is extremely vigorous, with constant roiling and semi-continuous spattering. Spatter deposited on the walls around the lava surface creates a hot, unstable surface, which can be seen to disintegrate as large blocks break off and fall into the lava.