Mount Cayley
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| Mount Cayley | |
|---|---|
 Mount Cayley as seen from its southeast slopes |
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| Elevation | 7,825 ft (2,385 m) |
| Location | Garibaldi Volcanic Belt, British Columbia, Canada |
| Range | Cascade Volcanic Arc, Pacific Ranges |
| Prominence | 674 m |
| Coordinates | |
| Topo map | NTS 92J/03 |
| Type | Stratovolcano |
| Age of rock | Pleistocene |
| Last eruption | 20,000 BP |
| First ascent | 1928 E. Brooks, T. Fyles, W. Wheatley |
| Easiest route | rock/ice climb |
Mount Cayley is an eroded stratovolcano in the Pacific Northwest region of Canada. It is located 11 km southwest of Callaghan Lake and 24 km west of Whistler. In 1984, a small debris flow at Mount Cayley dammed the Squamish River. There are several hotsprings and anomalous geophysical properties around Mount Cayley, 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).
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[edit] Geology
Mount Cayley is part of the Pacific Ring of Fire that includes over 160 active volcanoes. It is in the Garibaldi Volcanic Belt in southwestern British Columbia. Mount Cayley contains several complex features which probably represent multiple eruptions under different conditions and are difficult to classify. Mount Cayley could have possible eruptions in the future. Mount Cayley consists of poorly lithified pyroclastic rocks and lavas, which underwent three stages of volcanic activity.
Mount Cayley is a 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 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 and the Explorer Plate melts under the pressure, it creates pools of lava that drive up the Pacific Ranges and the Cascade Range and power periodic eruptions in there volcanic peaks.
[edit] Volcanic hazards
A scenario of an eruption of Mount Cayley shows how western Canada is vulnerable to an eruption. The scenario is based on past activity in the Garibaldi Volcanic Belt and involves both effusive and explosive eruptions. The scenario impact is largely a result of the concentration of vulnerable infrastructure in valleys. Because Mount Cayley has poorly consolidated slopes, it has been the site of two major historical debris flows, however there is also prehistoric landslide deposits present at the mountain. Mount Cayley is one of the top 10 Canadian volcanoes with recent seismic activity, the others include: Castle Rock, Mount Edziza, Hoodoo Mountain, Lava Fork Valley, Crow Lagoon, Mount Silverthrone, Mount Meager, Wells Gray-Clearwater Volcanic Field and Mount Garibaldi.
[edit] Geological history
[edit] Ancestral stages of eruptive activity
The mountain grew in three phases. Cayley's original phase of activity is characterized by a compound stack of plagioclase, hypersthene, hornblende, phyric dacite flows, tephra, and breccia, which are hydrothermally changed to an unstable degrees. The Vulcan's Thumb phase followed, named for the biggest of a number of slight peaks extend beyond from Pyroclastic Peak. Its creation consist of vent breccia, massive lava flows, and agglutinated breccia of plagioclase, hypersthene, hornblende, biotite, phyric dacite deposited as part of an edifice that raised upon the southwestern edge of the ancestral Mount Cayley. The third phase of activity constructed two minor plagioclase-hypersthene-biotite-phyric dacite lava domes, associated flows and tephra pieces that are uncovered in the Shovelnose Creek valley. There are no noticeable suggestions of volcano-ice contacts at Mount Cayley.
[edit] Subsidiary peaks
The broad top of Mount Cayley contains five named summits. The highest is the main summit of Mount Cayley. The second highest summit is Pyroclastic Peak, 2,349 m (7,707 ft), a steep, rotten volcanic peak immediately south on the ridge from Mount Cayley. The third highest highest summit is Powder Mountain, 2,347 m (7,700 ft) , a gentle volcanic dome north of Mount Cayley. The fourth highest summit is Vulcan's Thumb, 2,290 m (7,500 ft). The lowest of the five summits is Wizard Peak, 2,251 m (7,385 ft), a long eastwest ridge, with a very steep cliff on the north face.
[edit] Mount Cayley Volcanic Field
The Mount Cayley Volcanic Field is a volcanic field, located in the central part of the Garibaldi Volcanic Belt, which consists of a series of intermediate composition Miocene to Pleistocene volcanic centers. The field contains tuyas and subglacial domes, which caused subglacial eruptions.
Little Ring Peak is a volcano that has not been previosly studied in the field. It contains 70% of brown glass, with sparse plagioclase phenocrystals and contains a tuya-like form, but its inner stratigraphy is yet unknown. It is located at the northernmost known extent of the Mount Cayley Volcanic Field.
Cauldron Dome is an almost flat-topped pile of coarsely plagioclase-orthophyroxene-phyric andesite flows and is similar to a tuya.
Crucible Dome is a tuya. It last erupted during the Pleistocene.
Mount Brew is a subglacial mound. Mount Brew is the highest of the summits immediately 12 km south of Lillooet in the Garibaldi Volcanic Belt.
Mount Fee is a volcanic neck. It is located 13 km south of Callaghan Lake and 21 km west of Whistler. The neck of Mount Fee is two sharp blades of volcanic rock at the head of Brandywine Creek. The south tower of Mount Fee is the highest.
Pali Dome is a subglacial volcano, located north of Mount Cayley. It is partially obscured by ice and is dominated by coarsely plagioclase-hypersthene-phyric-andesite flows.
Slag Hill is a subglacial mound. It consists of glassy, augite-phyric basaltic andesite in steep-sided, glassy, finely jointed domes and one small, flat-topped bluff.
Ring Mountain is a tuya. It has a horseshoe shaped crater, located on the east side of the upper Squamish River.
Ember Ridge is a subglacial mound. Ember Ridge last erupted during the Pliocene and is made of series of steep-sided domes of glassy, complexly jointed, hornblende-phyric basalt.
[edit] See also
[edit] External Links
- Mount Cayley in the Canadian Mountain Encyclopedia
- Skiing the Cascade Volcanoes and Beyond
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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 |
