Mount Silverthrone
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| Mount Silverthrone | |
|---|---|
| Elevation | 3,160 metres (10,367 feet) |
| Location | Garibaldi Volcanic Belt, British Columbia, Canada |
| Range | Cascade Volcanic Arc, Pacific Ranges |
| Prominence | 974 m |
| Coordinates | |
| Topo map | NTS 92M/09 |
| Type | Caldera, Lava domes, Pyroclastic cones |
| Age of rock | Holocene |
| Last eruption | Unknown, possibly younger than 1000 AD |
| First ascent | 1936 Don Munday, Phyllis Munday, H. Hall, Hans Fuhrer |
Mount Silverthrone (officially gazetted as Silverthrone Mountain) is a circular 20 km wide, deeply dissected caldera complex in Regional District of Mount Waddington, British Columbia, in the Pacific Northwest region of Canada. It is located over 200 miles (320 km) northwest of the city of Vancouver and about 30 miles (50 km) west of Mount Waddington. It is the highest summit in the Ha-Iltzuk Icefield, which is the largest icefield in the Coast Mountains, although many mistakenly believe it to be part of the Cascade Range (It is a member of the Garibaldi segment of the Cascade Volcanic Arc, but not of the Cascade Range). Mount Silverthrone is also 3160 m high, making it the highest known volcano in Canada.[citation needed]
Mount Silverthrone is one of the top 10 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 and Mount Garibaldi.
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[edit] Geology
Mount Silverthrone is part of the Pacific Ring of Fire that includes over 160 active volcanoes. It contains rhyolitic, dacitic and andesitic lava domes, lava flows and breccia.
Mount Silverthrone is the northernmost member in the chain of 18 large volcanic peaks that run from southwestern British Columbia to northern California. The peaks formed in the past 35 million years as the Juan de Fuca Plate and the Explorer Plate to its south-west have been subducting under the North American Plate, known as the Cascadia subduction zone. As the oceanic crust of the Juan de Fuca Plate melts under the pressure, it creates pools of lava that drive up the Pacific Ranges and power periodic eruptions in its volcanic peaks.
[edit] Eruptive history
Most of the calderas eruptions occurred during the last ice age. 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. Anomalously old Potassium-Argon dates of 1.0 and 1.1 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 km upstream from the mouth of 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.
[edit] See also
[edit] External links
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| BC: Mount Silverthrone | Mount Meager | Mount Cayley | Mount Garibaldi WA: Mount Baker | Glacier Peak | Mount Rainier | Mount St. Helens | Mount Adams OR: Mount Hood | Mount Jefferson | Three Sisters | Broken Top | Mount Bachelor | Newberry Volcano | Mount Thielsen | Mount Mazama | Mount McLoughlin CA: Medicine Lake Volcano | Mount Shasta | Lassen Peak |
