A photo of The Catacombs.

This entrance to the "Catacombs" lava tube is relatively small compared to the others in the park. Note the blocky character of the lava flow above the entrance to the lava tube. This is typical of an "a'a" type lava flow. The blocky texture forms from the accumulation of congealed lava on the surface of a moving lava flow. Lava tubes typically form in lava flows where the surface material has solidified and became stabilized, but fluid molten lava continues to flow or drain in the subsurface (Grimes, 2005).