Slag Hill

Slag Hill in British Columbia is a subglacial volcano in the Mount Cayley volcanic field, shaped by both magma and ice. Its steep-sided, finely jointed domes and small flat-topped bluff are composed of glassy, augite-phyric basaltic andesite, and their quench features show lava cooled rapidly against glacial ice. Formed during the Pleistocene, Slag Hill preserves clear evidence that repeated glaciation affected how its volcanic material erupted and survived. A later lava flow on its western lobe lacks signs of ice contact, indicating an eruption after the last glacial period, less than 10,000 years ago. It remains a notably clear example of volcanism interacting with glaciation in western Canada.

British Columbia · Canada