Featured Article Summary #136

The Silverthrone Caldera, also known as the Silverthrone Caldera Complex, is a volcano in British Columbia, Canada, located in the Pacific Ranges of the Coast Mountains. It is about 2.5 by 2.5 (units not specified) in size and has been heavily eroded, creating rugged terrain, with an elevation reported as 2860 m or up to 3160 m. Meltwater streams and rivers flow from the volcano, including Pashleth, Selman, and Catto creeks, and the Kingcome and Wakeman rivers, and the caldera includes several named peaks and mountains. Its rocks include rhyolites, dacites, andesites, and basaltic andesites, grouped into three main age units, though much of the higher ground is covered by glacial ice. Since 1980, small shallow earthquakes have been recorded, but they have not been shown to be caused by magma, and the biggest possible risk from future eruptions is to air traffic. Indigenous peoples also used its obsidian, and although studies began in the 1960s and geothermal potential was assessed in the 1970s, the volcano’s remote location means its eruption history is still not well understood. The Silverthrone Caldera has also been called the Silverthrone Caldera Complex and the Silverthrone Depression, while related terms like “Silverthrone volcanic complex” or “volcanic field” describe the caldera and its volcanic rocks. These names come from Silverthrone Mountain, a nearby volcanic feature reported as early as 1933, and the 1968 Geological Survey of Canada report used the name Mount Silverthrone volcanic complex based on work by Jack Souther. The caldera’s name is shared with Silverthrone Glacier, and “Silverthrone” is a descriptive name for the icy landscape, possibly coined by Don Munday after his 1936 first ascent of Silverthrone Mountain. Silverthrone Caldera is in southwestern British Columbia, Canada, about 55 km north of Kingcome Inlet and 60 km northwest of Knight Inlet. It sits in rugged, ice-filled terrain of the Pacific Ranges, where glaciers and large icefields cover higher elevations and some bedrock is exposed. The climate is very wet because moist Pacific air rises over the mountains and releases heavy rain or snow, which supports wet forests, while alpine plants only grow in a narrow zone near the icefields; there are no nearby settlements, though logging and summer fishing camps occur. Rivers and creeks drain the Silverthrone Caldera from several glaciers into larger waterways and eventually to Kingcome Inlet and Rivers Inlet. Key systems include the Kingcome River (fed by Trudel, Charnaud, and Pashleth pathways) and the Pashleth–Machmell–Rivers Inlet route, along with the Selman, Wakeman, and Catto creeks feeding the Wakeman River and Wakeman Sound. The Silverthrone Glacier also flows southeast into Klinaklini Glacier, which leads to the West Klinaklini River. Silverthrone Mountain is the highest point in the Silverthrone Caldera, with reported summit heights ranging from about 2860–2865 m up to 3160 m. Other peaks inside or near the caldera include Mount Somolenko, Mount Overill, Mount Kinch, Petrovsky Peak, Mount Ardern, Mount Squire, and Mount Calli; most are made of volcanic rock and many are named for Canadian soldiers killed in World War II. Together these mountains form the Silverthrone Group, stretching from rivers and Owikeno Lake to the Pacific Ocean and Knight Inlet. Many peaks are volcanic, though some like Mount Fitzgerald are granite, and the tallest in the group are Silverthrone Mountain, Rampart Peak, Crumble Peak, and an unnamed 2730 m peak.