Powder Mountain Icefield

From Wikipedia, the free encyclopedia

The Powder Mountain Icefield, also called the Powder Mountain Icecap and the Cayley Icefield, is a glacial field in the Pacific Ranges of southwestern British Columbia, Canada, about 20 kilometres west of Whistler and about 90 kilometres north of Vancouver. On the west side of the icefield is the valley of the Squamish River, while on its east is the basin of Callaghan Creek, which is the setting for the Nordic facilities for the 2010 Winter Olympics.

The icefield is studded by several volcanic formations, including the active volcano Mount Cayley. Other summits are Powder Mountain, Brandywine Mountain and Mount Fee. Mount Callaghan, a dormant volcano, is just northeast of the icefield. Mount Brew is just to its south.

During the 1980s a resort proposal to build lifts onto the icefield, with a base village at Callaghan Lake, was shot down in the course of environmental and economic feasibility hearings by opposition from the resort at Whistler. Its promoter Nan Hartwick claimed that then-Premier Bill Vander Zalm interfered in the study process but this was never much investigated by the media before the end of the Vander Zalm regime.

[edit] Geology

Numerous subglacial eruptions beneath the Powder Mountain Icefield have formed many distinctive subglacial volcanoes that contain abundant glass and fine-scale jointing from rapid cooling of lava, such as Ember Ridge and Slag Hill. Mineralogically, the volcanics range from andesite to rhyodacite, and chemically, the rocks span a range from andesite to dacite. Glassy volcanic rocks are abundant, with glass contents as high as 70%. Volcanoes such as Ring Mountain were formed when magma intruded into and melted a vertical pipe in the overlying Powder Mountain Icefield. The partially molten mass cooled as a large block, with gravity flattening its upper surface, forming a flat-topped, steep-sided subglacial volcano called a tuya.