Halema`uma`u lava lake draining event

movie shows a draining event in the Halema`uma`u lava lake. Filling and draining cycles have been observed before here, but this video is one of the clearest examples thus far. The video is shown at actual speed, with draining taking about 40 seconds. Note the draining is highly unsteady, and proceeds in a step-wise fashion. These cycles of filling and draining are due to the episodic release of accumulated gas in the conduit.