Mount Meager

From Wikipedia, the free encyclopedia

Mount Meager
Elevation 2,645 metres (8,681 feet)
Location Garibaldi Volcanic Belt, British Columbia, Canada
Range Cascade Volcanic Arc, Pacific Ranges
Prominence 220 m
Coordinates 50°37′54.0″N, 123°30′16.0″WCoordinates: 50°37′54.0″N, 123°30′16.0″W
Topo map NTS 92J/12
Type Complex volcano
Age of rock Pliocene
Last eruption 2350 BP
First ascent 1931 N. Carter; A. Dalgleish; T. Fyles; M. Winram
Easiest route rock/ice climb

Mount Meager (sometimes mistakenly spelled Meagre or Meagher) is a potentially active complex volcano in the Pacific Ranges of Squamish-Lillooet Regional District, British Columbia, Canada. It is part of the Cascade Volcanic Arc, but is not in the geographic Cascade Range. It is located 150 km (95 mi) north of the city of Vancouver and 65 km (40 mi) northwest of Pemberton. Mount Meager has at least 8 vents, the youngest of which is on the northeast side of the mountain. This volcano is known for major catastrophic eruptions, similar to Mount St. Helens.

Mount Meager 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, Wells Gray-Clearwater Volcanic Field and Mount Garibaldi.

Mount Meager was a named after J.B. Meager, who owned timber licenses on Meager Creek. Before its present name, it was known as the more fitting Cathedral Mountain.

Contents

[edit] Geology

Mount Meager is the second largest volcano in the Garibaldi Volcanic Belt, after Mount Garibaldi. It is Pliocene-to-Holocene in age and is part of the Pacific Ring of Fire that includes over 160 active volcanoes. It has produced basaltic to more evolved andesitic, dacitic and rhyolitic magmas. It is the youngest of four overlapping stratovolcanoes that rest on a 400 m high ridge of nonvolcanic crystalline and metamorphic rock. There are multiple eroded summit lava domes and volcanic necks. Quaternary basalts underlying the uppermost 22 km of the Elaho valley originated at the 1375 m level in the South Fork Meager River.

Mount Meager is a member in the chain of volcanic peaks that run from southwestern British Columbia to northern California. The volcanoes formed over 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 at the Cascadia subduction zone. As the oceanic crust of the Juan de Fuca and the Explorer Plate melts, it creates magma that penetrates the crust of the Cascade Range and southwestern Coast Mountains, causing periodic eruptions of the volcanoes.

[edit] History

The natives of the zone possibly visited the Mount Meager area to hunt goats, and probably visited the Meager Creek Hot Springs. The first recorded ascents of the Mount Meager volcanic complex were made by the earliest Vancouver climbers Tom Fyles, Neal Carter, Alec Dalgliesh and Mills Winram. The crowd made contact with the Lillooet River floodplain on horseback, having been outfitted by a Mr. Perkins of Pemberton. The crowd climbed most of the major summits of Mount Meager with the exclusion of the impressive peak of Perkins Pillar, and the unstable Mount Job, which is difficult to come near from the main summits of the volcanic complex.

Mount Meager suffered a long period of quiescence following the 1931 visit. It was not until the early 1970s, when logging roads came up to the volcanic complex, that a restitution of interest took place.

[edit] Geological history

[edit] 2350 BP Eruption of Mount Meager

Mount Meager is the volcano with the most recent, major catastrophic eruptions in British Columbia from a vent on the north-east side of Plinth Peak that was similar to the 1980 eruption of Mount St. Helens and the ongoing eruption of Soufrière Hills in the Caribbean. This activity produced a diverse sequence of volcanic deposits, well exposed in the bluffs along the Lillooet River. The eruption was episodic, and the formation comprises airfall pumice, pyroclastic flows, welded breccias, lahars and an andesitic lava flow. The eruption was so great that thin, very finegrained, distal deposits of tephra have been identified in Alberta, 530 km from the vent and sent an ash column at least 20 km high into the stratosphere. An unusual, thick apron of welded vitrophyric breccia may represent the explosive collapse of an early lava dome and deposited ash several meters in thickness near the vent area. The eruption also blocked the Lillooet River, setting the stage for catastrophic failure of the upper part of the formation and resulted in an massive outburst flood.

[edit] Early phase pyroclastic flow deposit

A pyroclastic flow deposit from the major catastrophic eruption, completely overlies fallout pumice in displayes along the Lillooet River. The group is surrounding- to clast-supported, enormous, non-indurated, and consists of subrounded to rounded pumice blocks in a fine grey clastic surroundings. In some exposures it displays simple inner makeup or arrangement. The build up near the vent area is normally 3 to 10 m thick. The most proximal exposure is close to Keyhole Falls.

[edit] Pyroclastic fall deposit

Pyroclastic fall deposits, up to 80 m thick from the major catastrophic eruption, covers the slopes in the area of Mount Meager. The pumice fragments are light grey, fibrous and regularly have reddish or orange-coloured resembling cores and weathering to creamy white. The large fragments are spreading widely and occupying a great area of splintered, and surface breadcrust textures are common. About 1–5% of the pumice fragments are banded from white to dark grey. The pumice deposits are mined at several locations on its northeast flank and is very suitable for as a skin care product. The pumice is hand picked at the volcano's vent, where it is naturally purest and is the only pumice mine produced in Canada.

[edit] Lava flows

The most recent deposit from the major catastrophic eruption, is a small glassy, porphyritic dacite lava flow, which is 2 km long and varies from 15 to 20 m thick. The lava flow is weakly banded and ranges in vesicularity from almost pumiceous at the top to extremely dense at the base. The flow is heavily vegetated, but it still has its original form and is well preserved. The location of the vent where the lava flow came from is inferred to be close to the point where the lava outcrop narrows and disappears.

[edit] Devastation Glacier Debris Avalanche

The Devastator Glacier Debris Avalanche on July 22, 1975, multiple cycles of landslide occurrences took plate at Devastation Glacier near Pemberton, British Columbia when distorted Quaternary volcanic rock and glacier ice was gone from the west edge of Pylon Peak. Only 4 people were killed by the landslide. The occurrences were began by a catastrophic rockslide, containing distorted Quaternary pyroclastic rocks, which continued down Devastation Creek valley as a high rate debris avalanche. The debris avalanche recoiled back and forth flanked by the valley walls rising up to 100 m above the valley floor at the outside of curves in the valley before coming to rest at Meager Creek.

[edit] Meager Creek Hot Springs

Mount Meager is hot under the surface. The surface water goes under the volcano and becomes heated, then rises along fractures to reach the surface to form the Meager Creek Hot Springs. The hot springs are located west of Pemberton. The water at the Meager Creek Hot Springs have been tested for a hot water plumbing system as a geothermal energy sourse. The hot springs are very popular and are under considerable pressure from heavy use from people and local developments. The Meager Creek Hot Springs are relatively easily accessible from Whistler and Vancouver, but the bridge into the recreation site was destroyed by flooding, effectively closing the site.

[edit] Hazards of Mount Meager

[edit] Eruptions

Past eruptions at Mount Meager were Plinian style eruptions which suggests that Mount Meager poses a significant treat to long distances across southern British Columbia and southern Alberta. Lahars could easily travel as far as Pemberton, which is only 60 km from the volcano. Another Plinian style eruption from Mount Meager would have a significant impact on local mining, logging and air traffic. Mount Meager has had four episodes of activity, 1.9 to 2.2 million years, <1.9 and>0.5 million years, 1.0 and 0.5 million years and 0.15 to 0.002 million years ago. There haven't been any signs of renewed activity at Mount Meager, although it is a potentially active complex volcano. The first signs of activity at Mount Meager would probably be abundant shallow earthquakes, which may be accompanied by changes in the temperature or the location of fumaroles and hotsprings. These signs generally occur well in advance of a potential eruption, although the volcanic hazard at this time is low.

Some hydrothermal activity remains at Mount Meager, suggesting that Mount Meager is still alive and may erupt in the future.

[edit] Landslides

Landslide hazards are high at Mount Meager. It has been an area with huge landslides during the Holocene. The landslides that came from the mountain were based on two phases, an early debris flow resulting from failure of hydrothermally altered pyroclastic rock at mind levels on the mountain and a later rock avalanche from a higher sourse. Both of the debris flows from the mountain likely traveled down into Meager Creek, and preliminary evidence from drilling indicates the 4400 year old event traveled down into the Lillooet River areas that are now settled and where human population is rapidly increasing. The mobility of the debris flows was due to the high content of fine, weathered volcanic sediment and the accessibility of plenty water. The landslides might have been triggered by the upwelling of magma to shallow depths within Mount Meager or by the movement of earthquakes. However, the landslides at Mount Meager may have also occurred without specific triggers following extended periods of long term weakening of the volcanic rocks on Mount Meager. It is possible, however, that these huge landslides could again flow down into the Lillooet River or Meager Creek and destroy human population.

[edit] Subsidiary peaks

The broad top of Mount Meager contains six named summits. The highest is called Plinth Peak. The second highest summit is the main summit of Mount Meager, 2,646 m (8,681 ft), the third highest summit is Capricorn Mountain, 2,569 m (8,429 ft), which consists of a boomerang shaped ridge, with one summit on each end of the boomerang. The fourth highest summit is Mount Job, 2,493 m (8,180 ft), which is a steep pile of rubble held together by volcanic ash and sand. The fifth of the five summits is Pylon Peak, 2,473 m (8,112 ft), at the southern edge, which overlooks Meager Creek Hot Springs. The lowest of the six summits is Devastator Peak, 2,327 m (7,635 feet), this peak is seen as an impressive towering horn while from other angles it looks like a minor bump.

[edit] Mount Meager Volcanic Field

The volcanoes within the field include:

[edit] See also

[edit] References

    Image:Mount Rainier from southwest mini.jpg
    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
    Retrieved from "http://en.wikipedia.org../../../m/o/u/Mount_Meager_d41c.html"
    In other languages