Mount Silverthrone
From Wikipedia, the free encyclopedia
| Mount Silverthrone | |
|---|---|
| Elevation | approx. 2,865 m (9,400 ft) |
| Location | British Columbia, Canada |
| Range | Pacific Ranges |
| Prominence | approx. 975 m (3200 ft) |
| Coordinates | |
| Topo map | NTS 92M/09 |
| Type | Caldera, Lava domes, Pyroclastic cones |
| Volcanic arc/belt | Cascade Volcanic ArcPemberton Volcanic Belt |
| Age of rock | Holocene |
| Last eruption | Unknown; possibly younger than 1000 |
| First ascent | 1936 Don Munday, Phyllis Munday, H. Hall, Hans Fuhrer |
| Listing | List of volcanoes in CanadaList of Cascade volcanoes |
Mount Silverthrone is a circular 20 km (12 mi) wide, deeply dissected caldera complex in Regional District of Mount Waddington, British Columbia, located over 320 km (199 mi) northwest of the city of Vancouver and about 50 kilometres (30 mi) west of Mount Waddington, British Columbia, Canada. It is the highest peak in the Ha-Iltzuk Icefield, which is the largest icefield in the Coast Mountains south of the Alaska Panhandle. The complex and the surrounding area may be the northernmost section of the Cascade Volcanic Arc, but scientific study has been very limited due to its extremely remote location. Some geological references suggest that it represents the northernmost of the Cascade Volcanic Arc, because the Pemberton Volcanic Belt is usually merged with the Garibaldi Volcanic Belt,[1][2][3] but its relationship to volcanism caused by the Cascadia subduction zone (ie. the Cascade Volcanic Arc) has not been firmly established. Silverthrone may also be the highest volcano in Canada, but even its elevation is not definitely known. Some references state an elevation as high as 3,160 m (10,367 ft), but the current topographic map shows contours only as high as 2,865 m (9,400 ft), and no spot elevation is given. In addition, it is unclear whether the highest point is of volcanic origin or not, since the summit is covered with permanent snow and ice, and the composition of the underlying rock is unknown.
Mount Silverthrone is officially gazetted as Silverthrone Mountain, but Wikipedia convention is to go with the more commonly-used form. For example, Fairweather Mountain officially is generally referred to as Mount Fairweather. Mount Silverthrone is perhaps the most heavily glaciated volcanic complex in southwestern British Columbia and has a topographic prominence of approximately 975 m (3,199 ft), greater than any other volcano in southwestern British Columbia. The first mountaineering visit at Mount Silverthrone was by the famous pioneering climbing group of Don and Phyllis Munday in 1936 by walking up the Klinakini Glacier from the head of Knight Inlet.
Because Silverthrone is heavily glaciated, Don Munday called the volcano "home of the snows".[4] It has notoriously wet weather. This is why the Klinaklini Glacier descends to only about 300 m (984 ft) above sea level. The extensive icefields around Mount Silverthrone are receding and are small compared to their former extent, but they are an impressive indication of how much of British Columbia looked 10,000 years or more ago. Silverthrone contains one of the few calderas buried beneath the ice caps of western Canada, another example is Mount Edziza in far northwestern British Columbia, which is almost 2 km (1 mi) wide.
Contents |
[edit] Geology and eruptive history
The Mount Silverthrone caldera complex contains rhyolitic, dacitic and andesitic lava domes, lava flows and breccia.[5] It lies within the Coast Plutonic Complex, which is the single largest contiguous granite outcropping in the world. The plutonic and metamorphic rocks extend approximately 1,800 kilometers on the coast of British Columbia, southwestern Yukon and southeastern Alaska. In addition, Garibaldi, Meager, Cayley and Silverthrone areas are of recent volcanic origin. The volcanic terrain in the Silverthrone area is very similar to the Mount Meager volcanic complex. However, there is much more ice.
Most of the caldera's eruptions occurred during the last ice age[6] and the products have since been heavily eroded. Mount Silverthrone was episodically active during both Pemberton and Garibaldi Volcanic Belt stages of volcanism. The bulk of the complex appears to have been erupted between 0.1 and 0.5 million years ago, but postglacial andesitic and basaltic-andesite cones and lava flows are also present.[5] Anomalously old Potassium-argon dates of 1.0 and 1.1 million years were obtained from a lava flow in the postglacial Pashleth and Machmel Creek valleys. This flow is clearly much younger than the K-Ar date and high-energy glacial streams have only begun to etch a channel along the margin of the flow. A radiocarbon date from barnacles 8.5 kilometres (5 mi) upstream from the mouth of the Machmel River and buried by the flow yielded an age of 12,200 +/- 140 years. This is a maximum age for the lava flow, which could be much younger.[5] The last eruption from the caldera produced a lava flow that ran up against ice in Charnaud Creek. The lava flow was dammed by the ice and made a cliff with a waterfall up against it.[7] This andesitic lava flow represents the very edge of the volcanic complex. The thin columns indicate cooling was comparatively rapid while the long faces indicate that the large slab cooled as a unit. Additionally, the entablature is found on the bottom, the opposite of what can be seen in the more well-known flood basalts in the Chilcotin or in the Washington/Oregon desert. So it cooled from the bottom up rather than the top down.
Mount Silverthrone is one of the top 11 Canadian volcanoes with recent seismic activity, the others include: Castle Rock, Mount Edziza, Mount Cayley, Hoodoo Mountain, Lava Fork Valley, Crow Lagoon, Mount Meager, Wells Gray-Clearwater Volcanic Field, Mount Garibaldi and Nazko Cone.
[edit] Skiing and recreation
Skiing on Mount Silverthrone includes skiing on the largest ice field in the southern Coast Mountains, the Ha-Iltzuk Icefield. It is skiable over 1,500 meters (5,000 feet), possibly over 2,700 meters (9,000 feet) down to the Pacific Ocean.[6] The easiest access to Mount Silverthrone is by air travel, starting from the rural community of Tatla Lake, landing on the major part of the Ha-Iltzuk Icefield. Air travels can also be made into logging camps at Owikeno Lake to the west or at the start of Knight Inlet to the southwest, followed by long hiking and skiing methods.
[edit] Mount Silverthrone Volcanic Field
- Machmel River Cone
- Charnaud Creek
- Mount Silverthrone
- Trudel Creek
[edit] See also
[edit] References
- ^ Canada Volcanoes and Volcanics Retrieved on 2007-11-28
- ^ Preliminary petrography and chemistry of the Mount Cayley volcanic field Retrieved on 2007-11-15
- ^ Volcanoes of Canada Retrieved on 2007-11-15
- ^ Ha-Iltzuk Icefield in the Canadian Mountain Encyclopedia. Retrieved on 2007-11-13
- ^ a b c Smithsonian Institution Global Volcanism Program: Mount Silverthrone Retrieved on 2007-11-12
- ^ a b Skiing the Pacific Ring of Fire and Beyond: Silverthrone Mountain Retrieved on 2007-11-12
- ^ Charnaud Waterfall Retrieved on 2007-11-13
[edit] External links
- Volcanoes of Canada Garibaldi Volcanic Belt (Silverthrone area)
- Catalogue of Canadian volcanoes - Silverthrone Caldera
- Mount Silverthrone in the Canadian Mountain Encyclopedia
- Mount Silverthrone is at coordinates Coordinates:
Major Cascade Volcanoes | ||
|---|---|---|
| British Columbia | Mount Silverthrone · Plinth Peak · Mount Meager · Mount Cayley · Mount Garibaldi | |
| Washington | Mount Baker · Glacier Peak · Mount Rainier · Mount St. Helens · Mount Adams | |
| Oregon | Mount Hood · Mount Jefferson · Three Sisters · Broken Top · Mount Bachelor · Newberry Volcano · Mount Thielsen · Mount Mazama (Crater Lake) · Mount McLoughlin | |
| California | Medicine Lake Volcano · Mount Shasta · Shastina · Mount Tehama · Lassen Peak | |
| Eruptions | 1980 eruption of Mount St. Helens · 2350 BP eruption of Mount Meager | |
simple:Mount Silverthrone
