Mount Garibaldi
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| Mount Garibaldi | |
|---|---|
 Mount Garibaldi as seen from Squamish |
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| Elevation | 2,678 metres (8,786 feet) |
| Location | Garibaldi Volcanic Belt, British Columbia, Canada |
| Range | Cascade Volcanic Arc, Garibaldi Ranges |
| Prominence | 855 m |
| Coordinates | |
| Topo map | NTS 92G/14 |
| Type | Stratovolcano |
| Age of rock | Pleistocene |
| Last eruption | Holocene (~10000 BP) |
| First ascent | 1907 A. Dalton; W. Dalton; A. King; T. Pattison |
| Easiest route | Glacier travel, snow climb |
Mount Garibaldi is a dormant stratovolcano in the southernmost Coast Mountains of British Columbia, 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). This heavily eroded dome complex is 64 kilometres (40 mi) north of Vancouver—overlooking the town of Squamish—and is located in Garibaldi Provincial Park.
According to Chief Ian Campbell, the original Sḵwxwú7mesh name for the mountain was Nch'kay. Garibaldi was then re-named after Giuseppe Garibaldi in 1860 by Captain George Henry Richards aboard the HMS Plumper[1]
Mount Garibaldi 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 Silverthrone, Mount Meager and the Wells Gray-Clearwater Volcanic Field.
Mount Garibaldi is the largest volcano in the Garibaldi Volcanic Belt of volcanic centers in southern British Columbia, and is one of the few Cascade volcanoes that is made exclusively of dacite (Glacier Peak is the other). The mountain has a unique asymmetrical shape due to the fact that its main cone was constructed atop part of a large glacier system that has since melted away. Unlike many of the other Cascade volcanoes to the south, Garibaldi does not dominate the surrounding landscape, which consists of many high, rugged peaks. Many residents of Vancouver are therefore not aware that there is a volcano closer to the city than the more easily visible Mount Baker in Washington State.
In modern times, the apron of material from the volcano's main vent extends at least 4.8 kilometres (3 mi) from its source in places that were covered by ice and in other areas its extent is less and its slope is steeper. After its slow collapse, a series of debris flows carried 2.5 cubic kilometres (0.6 mi³) of the mountain into the Squamish Valley where it covers 26 square kilometres (10 mi²) to a thickness of about 90 metres (300 ft). 3.3 cubic kilometres (0.8 mi³) of material remains in the volcano.
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[edit] Geology
Mount Garibaldi 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. 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 the Cascade Range and power periodic eruptions in there volcanic peaks.
The mountain grew in three phases. Garibaldi's first phase resulted in the creation of a broad composite cone made of dacite and breccia that has been potassium-argon dated to 250,000 years old. Parts of this ancestral volcano are exposed on Garibaldi's lower northern and eastern flanks and on the upper 240 metres (800 ft) of Brohm Ridge. Around where Columnar Peak and possibly Glacier Pikes are now located, a series of coalescing dacite domes were constructed. During the ensuing long period of dormancy, the Cheekye River cut a deep valley into the cone's western flank that was later filled with a glacier.
After reaching its maximum extent the Cheekye glacier along with part of the area's ice sheet were covered with volcanic ash and fragmented debris from Garibaldi. This period of growth began with the eruption of a dacite plug dome from a ridge surrounded by the several thousand foot ice sheet. As the plug dome rose, massive sheets of broken lava crumbled as talus down its sides. Numerous pyroclastic flows (super-heated mix of gas, ash, and pumice) accompanied these cooler avalanches, forming a fragmental cone 6.3 cubic kilometres (1.5 mi³) in volume and an overall slope of 12 to 15 degrees (erosion has since steepened this slope). Some of the glacial ice was melted by the eruptions, forming a small lake against Brohm Ridge's southern arm. The volcanic sandstones seen today atop Brohm Ridge were created by ash settling in this lake.
Glacial overlap was most significant on the west and somewhat to the south. Subsequent melting of the ice sheet and its component glaciers initiated a series of avalanches and mudflows on Garibaldi's western flank that moved nearly half of the original cone's volume into the Squamish Valley. Gaps left by melting ice caused minor to moderate cone distortion where the ice sheet was thin and major distortion where it was thick (the ice was thickest in and thus cone distortion was greatest over the buried Cheekye valley).
Soon before or after the buried ice had melted away, dacite lava quietly erupted from a crater north of the Atwell Peak plug dome and flowed down Garibaldi's north and northeastern flanks. About 0.6 cubic kilometres (0.15 mi³) of dacite erupted in Garibaldi's third period of activity. This lava covers the north flank and part of the western flank of the volcano.
[edit] Garibaldi Lake Volcanic Field
An unusual volcanic structure called The Table is located 5.5 kilometres (3.5 mi) north of Garibaldi. This several hundred foot high flat-topped volcano is made of layers of andesitic dacite that are arranged like a stack of more or less equal sized pancakes. The Table was formed in the late Pleistocene at a time when the Cordilleran ice sheet covered the region. As the volcano's lava rose it melted the part of the ice sheet above The Table's vent, creating space for the lava to move into. Repeated eruptions constructed the steep-walled stack of lava seen today.
The Black Tusk is a large spire of extensively eroded dark volcanic rock that is shaped like a Walrus tusk. Its origin is not known but it may have formed in a similar way as The Table.
On the west side of Squamish Valley a series of pinnacles stand near Squamish. The tallest of these is Castle Towers Mountain and may be a lava spine similar to those near Mount Pelée.
Cinder Cone stands 150 metres (500 ft) above a gap between two arms of Helmet Glacier on Garibaldi's flanks. During summer its crater is filled with a snow melt lake.
Opal Cone is the source of a 15 kilometres (9.3 mi) long broad dacite lava flow with prominent wrinkled ridges. The lava flow is unusually long for a silicic lava flow.
[edit] Subsidiary peaks
The broad top of Mount Garibaldi contains three named summits. The highest is the main summit of Mount Garibaldi. The seconded highest summit is Dalton Dome, 2,633 metres (8,638 ft), west of the main peak of Mount Garibaldi. The lowest of the three summits is Atwell Peak, 2,655 metres (8,711 ft), at the southern edge of the main peak of Mount Garibaldi. This peak is commonly called Mount Garibaldi when viewed from Squamish, since the main peak is hidden.
A feature on the North side of the mountain is known as The Tent, and another minor summit on the south side of the mountain is known as Diamond Head (sometimes Little Diamond Head) for its pyramid shape.
[edit] See also
- Mount Price
- Mount Meager
- Devastator Peak
- Mount Cayley
- Mount Silverthrone
- Crater Lake
- Mount Adams
- Mount Baker
- Mount Hood
- Mount Rainier
- Mount Shasta
- Mount St. Helens
- Garibaldi Ranges
- Cascade Volcanic Arc
- Garibaldi Volcanic Belt
[edit] References
- ^ The Results of Archaeological Inventory of the area between Elfin Lakes and Mamquam Lake. Garibaldi Provincial Park, southwestern B.C.. SFU Archaeology Local History. Retrieved on 2007-02-21.
- Fire Mountains of the West: The Cascade and Mono Lake Volcanoes, Stephen L. Harris, (Mountain Press Publishing Company, Missoula; 1988) ISBN-X
- Global Volcanism Program (Garibaldi)
- Geological Survey of Canada (Garibaldi)
[edit] External links
- Mount Garibaldi at the Canadian Mountain Encyclopedia
- Garibaldi Provincial Park at BC Parks
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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 |
