Pavonis Mons Summit Caldera

This image shows part of the summit caldera of Pavonis Mons. Pavonis is the middle of three Tharsis volcanos that form a line southeast of Olympus Mons and northwest of Vallis Marineris. On Earth volcanic calderas usually form when a massive eruption has emptied out the magma chamber and the roof of the chamber collapses into the resultant space. It is likely that summit calderas on Martian volcanoes form in a similar manner.