Subglacial Mound

A subglacial mound is a type of subglacial volcano formed when lava erupts beneath a thick glacier or ice sheet. Because the magma forming these volcanoes was not hot enough to melt a vertical pipe straight through the overlying ice, it instead forms hyaloclastite and pillow lava deep beneath the ice; once the glacier retreats, the volcano is revealed with a shape unique to its confinement within the ice. Such mounds are rare worldwide, confined to regions once covered by continental ice sheets that also had active volcanism during the same period, including Iceland, Antarctica and British Columbia.