While mapping the flow margins, HVO geologists found an opening into an old lava tube system that has been partly filled with episode 61g lava. Most of the cooled lava cascades were intact and sitting on top of rubble from the caved-in roof of the abandoned tube. The opening in the tube (right) was partially filled with new lava, but was still roughly 3 m (10 ft) high. Photo taken Wednesday, August 9, 2017 courtesy of USGS/HVO