An open lava tube. This collapsed feature often occurs when the outer edges of a flow are quickly cooled by contact with seawater. The insulated lava insideremains viscous and eventually recedes, creating a void.
4/10/2019 11:58:20 AM
Date: 2011 July 20
Credit: NOAA Okeanos Explorer Program, Galapagos Rift Expedition 2011