Mount Garibaldi

Mount Garibaldi
Mount Garibaldi as seen from Squamish
Elevation	m ( ft)
Location	Squamish, British Columbia, Canada
Range	Garibaldi Ranges
Prominence	m ( ft)
Coordinates	49°51′02″N, 123°00′17″WCoordinates: 49°51′02″N, 123°00′17″W
Topo map	NTS 92G/14
Type	Stratovolcano
Volcanic arc/belt	Cascade Volcanic Arc Garibaldi Volcanic Belt
Age of rock	Pleistocene
Last eruption	Holocene (~10,700-9,300 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. This heavily eroded dome complex is located within Garibaldi Provincial Park overlooking the town of Squamish, about 65 kilometres (40 mi) north of Vancouver. The volcano is part of the Garibaldi Volcanic Belt which is a segment of the Cascade Volcanic Arc, but it is not within the geographic boundary of the Cascade Range.

The first nations have numerous names for the mountain. One version is that the peak was known in summer as Ta Nch'qai' (the "Grimy One") because of its typical dusty appearance. There is no record of its winter name, if there was one. According to local Sḵwxwú7mesh Chief Ian Campbell, the Sḵwxwú7mesh language name for the mountain is Nch'kay. Garibaldi was then re-named after Giuseppe Garibaldi in 1860 by Captain George Henry Richards aboard the HMS Plumper.^[1] This story is that the mountain is considered sacred as it was a safe haven during the floods following the great ice ages.

Geology

Mount Garibaldi is the highest 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.

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 lava 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.

The north face of Mount Garibaldi rises above The Table and Garibaldi Lake

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 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.

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.

Subsidiary peaks

The broad top of Mount Garibaldi contains three named peaks, the highest of which is the 2,678 metres (8,787 ft) main summit named Mount Garibaldi. The second highest peak is the rounded Dalton Dome, 2,633 metres (8,638 ft), west of the main summit. The lowest of the three is the sharp pyramid of Atwell Peak, 2,620 metres (8,569 ft), at the southern edge of the summit plateau. This peak is commonly called "Mount Garibaldi" when viewed from Squamish, since the main peak is hidden behind it.

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. Diamond Head was the site of a ski proposal and small lodge, now derelict.

Garibaldi Lake Volcanic Field

Black Tusk viewed from the southeast

Main article: 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.

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.

Mount Price, west of Garibaldi Lake, 5 km south of Black Tusk, was formed in three stages of activity, dating back 1.1 million years, the latest of which produced two large lava flows from Clinker Peak during the early Holocene that ponded against the retreating continential ice sheet and formed The Barrier, containing Garibaldi Lake.

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.

See also

• Garibaldi Ranges
• Garibaldi Volcanic Belt
• Cascade Volcanic Arc

References

• Harris, Stephen L. (2005). Fire Mountains of the West: The Cascade and Mono Lake Volcanoes (3rd ed.). Mountain Press Publishing Company, 454 pp. ISBN 0-87842-511-X. 
• Wood, Charles A.; Jürgen Kienle, eds. (1990). Volcanoes of North America. Cambridge University Press, 354 pp. ISBN 0-521-43811-X. 
• Mathews, Bill; Monger, Jim (2005). Roadside Geology of Southern British Columbia. Mountain Press Publishing Company, 404 pp. ISBN 0-87842-503-9. 
• Global Volcanism Program (Garibaldi)
• Geological Survey of Canada (Garibaldi)

External links

• Mount Garibaldi at the Canadian Mountain Encyclopedia
• Garibaldi Provincial Park at BC Parks

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

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