HiRISE: Giant cave on a giant volcano

Pavonis Mons is a giant shield volcano similar to (although larger than) those on the Big Island of Hawaii. These volcanoes are mostly made of stacks of overlapping lava flows. These images and digital terrain model (DTM) show a collapse feature on Pavonis Mons. The walls of this conical pit are steep (about as steep as it is possible to get before loose material rolls downhill). The material that used to be here has drained downward through the opening seen in the center into a subterranean void and formed a debris pile. The top of… [More at link]