Mount Cayley
Mount Cayley | |
---|---|
Highest point | |
Elevation | 2,385 m (7,825 ft)[1] |
Prominence | 674 m (2,211 ft)[1] |
Parent peak | Mount Callaghan (2409 m)[1] |
Listing | Mountains of British Columbia |
Coordinates | 50°07′13″N 123°17′27″W / 50.12028°N 123.29083°W |
Geography | |
Country | Canada |
Province | British Columbia |
District | New Westminster Land District |
Range coordinates | 50°06′58″N 123°17′15″W / 50.11611°N 123.28750°W |
Parent range | Pacific Ranges |
Topo map | NTS 92J3 Brandywine Falls |
Geology | |
Formed by | Stratovolcano, lava domes |
Age of rock | Neogene-to-Quaternary |
Volcanic arc/belt | Canadian Cascade Arc Garibaldi Volcanic Belt |
Climbing | |
First ascent | 1928 by E. C. Brooks, W. G. Wheatley, B. Clegg, R. E. Knight and T. Fyles |
Mount Cayley is an eroded but potentially active
Part of the
Future eruptions are likely to threaten neighbouring communities with
Geography and geology
The volcano resides in the middle of a north–south trending zone of volcanism called the
Three main summits comprise the Mount Cayley massif.
As a stratovolcano, Mount Cayley is built up of solidified lava and ash from successive volcanic eruptions. It is predominantly
Deep seismic profiling 12.5 to 13 km (7.8 to 8.1 mi) below the volcano has identified a large bright spot, a reflector interpreted to be a mid-crustal magma chamber or body of very hot rock.[10][11] Similar mid-crustal reflectors have been identified under subduction zone volcanoes in Japan.[11]
Volcanic history
Mount Cayley has experienced volcanic eruptions sporadically for the last 4,000,000 years, making it one of the most persistent eruptive centres in the Garibaldi Volcanic Belt.
Eruptions during the three stages produced volcanic rocks of felsic and intermediate compositions, including andesite, dacite and rhyodacite.[5] The lack of evidence for volcano-ice interactions at Mount Cayley implies that all eruptive stages most likely took place prior to glacial periods. This contrasts with many neighbouring volcanoes, which contain abundant volcanic glass and fine-scale columnar jointing from contact with ice during eruptions.[4]
Initial volcanic activity of Mount Cayley 4,000,000 years ago corresponded with changes to the regional plate tectonics.[5][12] This involved the separation of the Explorer and Juan de Fuca plates off the British Columbia Coast, which had some significant ramifications for regional geologic evolution. After this reorganization ceased, volcanism shifted westward from the Pemberton Volcanic Belt to establish the younger and currently active Garibaldi Volcanic Belt. The westward shift in volcanism may have been related to steepening of the Juan de Fuca slab after the formation of the Explorer Plate.[12]
Mount Cayley stage
The early Mount Cayley stage was characterized by the eruption of felsic lava flows and pyroclastic rocks onto a crystalline basement.[7][13] Initial volcanism formed a southwesterly-dipping prism of dacite flows and tephra cut by several dikes and sills. These rocks have been hydrothermally altered to varying degrees and are light yellow or red in colour. They are well exposed in the prominent southwestern cliffs of the volcano.[7]
Subsequent activity deposited a series of massive dacite flows up to 150 m (490 ft) thick, which form the summit and northern slope of Wizard Peak. The Mount Cayley stage culminated with the emplacement of a central plug dome that forms the narrow jagged summit ridge of Mount Cayley. This edifice consists of similar intrusive dacite.[7]
Vulcan's Thumb stage
The next eruptive period, the Vulcan's Thumb stage, built an edifice that grew upon the southwestern slope of the ancestral Mount Cayley stratovolcano. This began with the eruption of massive dacite flows and blocky agglutinated breccias onto basement and older volcanic rocks of the Mount Cayley stage. These rocks partially form a ridge south of Wizard Peak and comprise the prominent summit ridge pinnacles of Pyroclastic Peak, including the Vulcan's Thumb.[7]
Later activity produced an overlying 1 km (0.62 mi) wide and 4 km (2.5 mi) long southwest-trending lobe of unconsolidated or poorly consolidated tephra. The tephra consists of ash and lapilli-sized fragments that have been heavily eroded to form vertical cliffs and ridges. Volcanism also deposited a 130 m (430 ft) thick sequence of blocky dacitic tuff breccia between Wizard Peak and Mount Cayley.[7]
Shovelnose stage
Volcanic activity of the final Shovelnose stage involved the eruption of two lava domes at the east and southeast margins of Mount Cayley in the upper Shovelnose Creek valley.[7] The southeast dacite dome forms 400 m (1,300 ft) high cliffs of small diameter columnar joints.[7] It was the source of a 5 km (3.1 mi) long dacite flow that extends down the Shovelnose and Turbid creek valleys to near the Squamish River.[6][7] The east lava dome was built upon blocky bedded tephra overlying basement rocks and consists of a steep-sided columnar jointed mass of dacite.[7]
Recent activity
Although Mount Cayley is not known to have had historical volcanic eruptions, low-level activity has continued into recorded history. Shallow earthquakes have occurred in the vicinity since 1985 and the Shovelnose and Turbid creek valleys contain two and three hot springs, respectively. The GSC therefore considers the volcano to be potentially active.[14] Temperatures ranging from 18 to 40 °C (64 to 104 °F) have been measured from the hot springs.[7]
The existence of hot springs indicate that
Landslide history
Because Mount Cayley is rich in coarse proximal pyroclastic deposits, some of them hydrothermally altered, it is especially prone to slope failure and
At least three smaller scale debris avalanches have occurred in historic time. A 5,000,000 m3 (180,000,000 cu ft) landslide occurred in 1963 with the failure of a large volcanic block consisting of poorly consolidated tuff breccia and columnar-jointed dacite. The mass slid into Dusty Creek where it quickly fragmented into an aggregate then travelled roughly 1 km (0.62 mi) downstream where it entered the broader flatter valley of Turbid Creek for an additional 1 km (0.62 mi). Both creeks were blocked by the event, resulting in the creation of lakes that eventually overtopped and breached the landslide dam to produce floods and possibly debris flows which in turn swept down Turbid Creek far beyond the landslide terminus.[9] In June 1984, a major rockslide and debris flow resulted from a 3,200,000 m3 (110,000,000 cu ft) collapse at the head of Avalanche Creek. The debris flow reached the mouth of Turbid Creek where it destroyed a logging road bridge and blocked the Squamish River, introducing massive quantities of sediment.[8] The third event took place along Turbid Creek in June 2014 and involved a debris flow that removed part of the Squamish River Forest Service Road.[14]
Human history
The area has been inhabited by First Nations for thousands of years. Both the Mount Cayley volcano and The Black Tusk on the opposite side of the Cheakamus River valley are called taḵ'taḵmu'yin tl'a in7in'axa7en by the Squamish people. In their language it means "Landing Place of the Thunderbird".[15] The Thunderbird is a legendary creature in North American indigenous peoples' history and culture.[16] When the bird flaps its wings, thunder is created, and lightning originates from its eyes. Mount Cayley and The Black Tusk are considered sacred to the Squamish people as they have played an important part of their history. Mountain bilberries, Canadian blueberries and oval-leaved blueberries, being a favored food of the Squamish people, were gathered in large berry fields on and near the massif.[15] Glassy rhyodacite collected from small outcrops on the slopes have been found in goat hunting sites and the Elaho rockshelter which have been collectively dated around 8,000 to 100 years old. Cayley rhyodacite has only been found in the northern parts of the Squamish Nation territory.[16]
There had been no
Mount Cayley has been investigated as a potential
Volcanic hazards
This section relies largely or entirely on a single source. (August 2022) |
Though Mount Cayley is currently quiet, it still poses potential hazards to nearby towns as well as logging and recreational areas.
If eruptive activity were to resume, scientists would likely be able to detect increased seismicity as magma makes its way through the crust. The abundance of seismic activity and the sensitivity of the existing Canadian National Seismograph Network in this area would alert the GSC and possibly trigger an expanded monitoring effort. As the magma nears the surface, the volcano would likely swell and the surface fracture, causing greatly increased vigour in the hot springs and the creation of new springs or fumaroles. Minor and possibly large landslides could occur and might temporarily block the Squamish River, as has happened in the past without earthquake shaking and intrusion-related deformation. Eventually the near-surface magma may cause phreatic explosions and debris flows. By this time Highway 99 would be closed, Squamish would be evacuated and Whistler would be at least considered for evacuation.[20]
In the event of an explosive eruption, an
Explosions might cease and be replaced by slow, continuous growth of a lava dome in the new crater. Rain and seasonal snow melt would regularly remobilize the tephra into lahars and these would continue to threaten the Squamish and Cheakamus valleys. The solidifying, spreading lava could then generate rockfalls and form a voluminous talus apron into the Squamish valley. As the lava dome spreads, it would periodically undergo gravitational collapse to generate dense pyroclastic flows into the Squamish and Cheakamus valleys. Ash elutriated from the pyroclastic flows would form plumes up to 10 km (6.2 mi) high, again dropping ash onto Pemberton and Whistler and causing disruptions to local air traffic. Infrequently, the lava dome might produce small explosions, ash plumes and pyroclastic flows. Squamish would remain evacuated, Highway 99 would remain closed and unrepairable and travel between Whistler/Pemberton and Vancouver would be forced to go via a much longer route to the east.[20]
Eruptive activity itself could go on for years, followed by years of declining secondary activity. The cooling lava would intermittently spall sections to produce pyroclastic flows. The fragmental material on the slopes and in valleys would be periodically remobilized into debris flows. Significant structural mitigation would have to be built to reclaim use of the Highway 99 corridor and Squamish area.[20]
See also
Notes
- [a] ^ According to Hildreth's definitions, proximal relief refers to the difference between the summit elevation and the highest exposure of old rocks under the main edifice, while draping relief marks the difference between the summit elevation and the edifice's lowest distal lava flows (excluding pyroclastic and debris flows).[6]
References
- ^ a b c d "Mount Cayley". Bivouac.com. Retrieved 2021-04-09.
- ^ "Mount Cayley". Peakbagger.com. Retrieved 2021-04-09.
- ^ a b "Cayley Volcanic Field". Global Volcanism Program. Smithsonian Institution. Retrieved 2018-05-02.
- ^ a b c Kelman, M. C., Russell, J. K., Hickson, C. J. (2001). "Preliminary petrography and chemistry of the Mount Cayley volcanic field, British Columbia", Current Research Part A, Geological Survey of Canada Paper 2001-A11, pp. 1, 2, 4, 5.
- ^ ISBN 0-521-43811-X.
- ^ ISBN 978-1-4113-1945-5.
- ^ a b c d e f g h i j k l m n o p q r s t Kelman, Melanie Catherine (2005). Glaciovolcanism at the Mount Cayley volcanic field, Garibaldi Volcanic Belt, southwestern British Columbia (PhD). University of British Columbia. pp. 4, 21, 24, 30, 31, 32, 34, 35.
- ^ ISSN 1480-3313.
- ^ ISSN 1480-3313.
- ^ a b Kimball, Sarah (2010). Favourability Map of British Columbia Geothermal Resources (MAS). University of British Columbia. pp. 21, 22, 24, 131.
- ^ ISSN 0148-0227.
- ^ .
- ^ ISSN 1480-3313.
- ^ a b c Southam, Dave (2014), Preliminary Debris Flow Assessment – June 29, 2014 Mud Creek Event Squamish River (9160), Approximate Station 21.1 km, Ministry of Forests, Lands and Natural Resource Operations, pp. 1, 4, 8
- ^ a b Reimer, Rudy (2003). "Squamish Traditional Use of Nch'kay Or the Mount Garibaldi and Brohm Ridge Area" (Document). First Heritage Archaeological Consulting. pp. 8, 17.
- ^ a b Reimer/Yumḵs, Rudy (2006). "Squamish Nation Cognitive Landscapes" (Document). McMaster University. pp. 8, 9.
- ^ "Mount Cayley". BC Geographical Names. Retrieved 2018-03-21.
- ^ a b c d Jessop, A. (2008). Review of National Geothermal Energy Program Phase 2 – Geothermal Potential of the Cordillera. Mount Cayley (Report). Geological Survey of Canada. p. 45.
- ^ a b Reader, John F.; Croft, Stuart A. S. (1983). Report on 1982 Temperature Gradient Drilling on Shovelnose Creek at Mount Cayley, Southwestern British Columbia (Report). Nevin Sadier-Brown Goodbrand Limited. p. 3.
- ^ S2CID 129461798
External links
- "Mount Cayley". Catalogue of Canadian volcanoes. Natural Resources Canada. 2009-03-10. Archived from the original on 2010-12-11. Retrieved 2018-05-06.