Silverthrone Caldera

The Silverthrone Caldera, also referred to as the Silverthrone Caldera Complex, is a poorly studied volcano in Range 2 Coast Land District of British Columbia, Canada. It lies within the Pacific Ranges of the Coast Mountains and reaches an elevation of 2,860 metres (9,380 feet), although some sources give the elevation as high as 3,160 m (10,370 ft). The caldera is about 25 by 20 kilometres (16 by 12 miles) in size and has been deeply eroded, resulting in the formation of rugged topography. Several glacial meltwater streams originating from the Silverthrone Caldera flow through valleys in the Pacific Ranges; among these streams are the Pashleth, Selman and Catto creeks and the Kingcome and Wakeman rivers. The volcano contains several named mountains, including Mounts Somolenko, Overill, Kinch, Squire, Ardern and Calli, as well as Petrovsky Peak and Silverthrone Mountain.

Volcanic rocks deposited by eruptions of the Silverthrone Caldera and associated vents include rhyolites, dacites, andesites and basaltic andesites. They are exposed in valleys, but at higher elevations, they are largely buried under glacial ice of the 3,600 km² (1,400 mi²) Ha-Iltzuk Icefield. These rocks comprise three geological units: a 750,000-year-old basal breccia unit, a 400,000-year-old unit of overlying lava flows and domes, and a less than 13,000-year-old series of lava flows and pyroclastic cones. Small magnitude, shallow earthquakes have been recorded near the volcano since 1980, but they have not been demonstrated to be magmatic in origin. The main potential hazard posed by future volcanism is to air traffic if explosive eruptions were to occur from the Silverthrone Caldera.

The Silverthrone Caldera was a source of obsidian for indigenous peoples during the pre-contact era. Geological studies have been conducted at the volcano since at least the 1960s, but its very remote location has impeded detailed fieldwork. As a result, the eruptive history of the volcano is poorly known and its affinity to the Garibaldi Volcanic Belt remains unclear. The Silverthrone Caldera was studied in the 1970s as a potential source of geothermal energy. It can be reached by helicopter or, with great difficulty, by trekking on foot through valleys.