USGS Video of Explosion
The side of the cliff collapsed into the lava bed causing a massive explosion. The pictures that I took of the eruptions preceding this slice are from the left side of the orange glow seen taken from the observation centre. While taken from the ground with a limited view of the lava field, the explosions captured are substantial.
The link to this and other videos can be found on the USGS site: http://hvo.wr.usgs.gov/multimedia/uploads/multimediaFile-1182.mp4