Ice Gopher. Anthony Powell.
Sink holes in the ice shelf re-freeze over winter, and when the ice expands as it freezes it causes these mini-volcano shapes to appear. Ice expands at roughly a 9:1 ratio when it freezes, so there was roughly 9 times the volume of this wee eruption in liquid water hidden just below the surface of the ice a few weeks before.
From Bases Machines and People