Volcanoes come with their own underground plumbing systems that move molten rock around and feed eruptions onto the surface. Sometimes these plumbing systems can drain causing collapses of the ground above them.

This image of Hephaestus Fossae shows a volcanic area where collapses like this happen. Chains of large elliptical pits mark the path that underground molten rock took. A much smaller isolated pit near the center of the image is probably a more recent collapse. This smaller pit is steep enough that the floor is shadowed, but with the right image processing we can still see the interior.

Written by: Shane Byrne