Mount Cayley
Encyclopedia
Mount Cayley is a potentially active stratovolcano
in Squamish-Lillooet Regional District of southwestern British Columbia
, Canada
. Located 45 kilometres (28 mi) north of Squamish
and 24 kilometres (14.9 mi) west of Whistler
in the Pacific Ranges
of the Coast Mountains
, it rises 2264 metres (7,427.8 ft) above the Squamish River
to the west and 1844 metres (6,049.9 ft) above the Cheakamus River
to the east.
Mount Cayley consists of ridge
s, rounded lava dome
s and sharp eroded rocky pinnacle
s with the highest reaching 2377 metres (7,798.6 ft) in elevation. It lies at the southern end of a field of glacial
ice called the Powder Mountain Icefield
.
of this territory, the mountain is called t'ak'takmu'yin tl'a in7in'a'xe7en. In their language it means "Landing Place of the Thunderbird". This name of the mountain refers to the legendary Thunderbird
, a creature in North American indigenous peoples' history and culture. Like Black Tusk
further south, the rock was said to have been burnt black by the Thunderbird's lightning. This mountain, like others located in the area, is considered sacred because it plays an important part in their history.
The first recorded ascent of Mount Cayley was made by the mountaineers E.C. Brooks, W.G. Wheatley, B.Clegg, R.E. Knight, and Tom Fyles in 1928. During this time, the party named the volcano after the late Beverley Cochrane Cayley, who was an ardent mountaineer of the executive committees of the British Columbia Mountaineering Club
and the Vancouver
section of the Alpine Club
for several years. Beverley Cayley was a friend of those in the climbing party, and died on June 8, 1928 at the age of 29 in Vancouver. Photographs of Mount Cayley were published in the Canadian Alpine Journal Vol XX in 1931.
outcropping in North America. The intrusive
and metamorphic rock
s of the Coast Plutonic Complex extend approximately 1800 kilometres (1,118.5 mi) along the coast of British Columbia, the Alaska Panhandle
and southwestern Yukon
. This is a remnant of a once vast volcanic arc
called the Coast Range Arc that formed as a result of subduction
of the Farallon
and Kula Plate
s during the Jurassic
-to-Eocene
periods. In contrast, Mount Cayley, Mount Meager
, Mount Garibaldi
and Silverthrone Caldera
are of recent volcanic origin.
Mount Cayley consists mostly of an igneous rock
with a high iron
content called dacite
, although another igneous rock, rhyodacite
, with intermediate composition of dacite and rhyolite
is also present. Unlike many of the other volcanoes further south, Cayley does not dominate the surrounding landscape, which consists of high, rugged peaks.
Mount Cayley began erupting about 4 million years ago and has grown steadily since then. Like all of the volcanoes further south, Mount Cayley has its origins in the Cascadia subduction zone
—a long convergent plate boundary that stretches from mid-Vancouver Island
to Northern California
. The subduction zone separates the Juan de Fuca
, Explorer
, Gorda
and North American Plate
s. Here, the oceanic crust
of the Pacific Ocean
sinks beneath North America
at a rate of 40 millimetres (1.6 in) per year. Hot magma
upwelling above the descending oceanic plate creates volcanoes, and each individual volcano erupts for a few million years. These volcanoes are commonly referred to as Cascade volcanoes because they were formed by Cascadia
subduction
.
The subduction zone has existed for at least 37 million years, and has created a line of volcanoes called the Cascade Volcanic Arc which stretches over 1000 kilometres (621.4 mi) along the subduction zone. Several volcanoes in the arc are potentially active. Lassen Peak
in California, which last erupted in 1917, is the southernmost historically active volcano in the arc, and Mount Meager
, just north of Mount Cayley, which erupted about 2,350 years ago, is generally considered the northernmost. A few isolated volcanic centers northwest of Mount Meager, such as the Silverthrone Caldera
, which is a 20 kilometres (12.4 mi) wide, deeply dissected caldera
complex, are considered by some geologists to be the northernmost member of the arc.
Mount Cayley is the largest and oldest volcanic complex of the Garibaldi Volcanic Belt
. Like other stratovolcano
es, it is composed of layers of hardened lava, tephra
, and volcanic ash. Eruptions are explosive in nature, involving viscous magma
, glowing avalanches of hot volcanic ash
and pyroclastic flow
s. The source magma of this rock is classified as acid
ic, having high to intermediate levels of silica (as in rhyolite
, dacite
, or andesite
).
Stratovolcanoes are a common feature of subduction zones. The magma that forms them arises when water, which is trapped both in hydrated minerals and in the porous basalt
rock of the upper oceanic crust, is released into mantle
rock of the asthenosphere
above the sinking oceanic slab. The release of water from hydrated minerals is termed "dewatering", and occurs at specific pressure/temperature conditions for specific minerals as the plate subducts to lower depths. The water freed from the subducting slab lowers the melting point
of the overlying mantle rock, which then undergoes partial melting and rises due to its density relative to the surrounding mantle rock, and pools temporarily at the base of the lithosphere
. The magma then rises through the crust
, incorporating silica rich crustal rock, leading to a final intermediate composition. When the magma nears the surface it pools in a magma chamber
under the volcano. The relatively low pressure of the magma allows water and other volatiles
(CO2, S2-, Cl-) dissolved in the magma to begin to come out of solution, much like when a bottle of carbonated water
is opened. Once a critical volume of magma and gas accumulates, the obstacle provided by the volcanic cone
is overcome, leading to a sudden explosive eruption
.
Cayley was formed in relatively early Pliocene
time compared to most other Cascade volcanoes, which were formed in the past two million years, and mostly in the past one million years or less. Cayley's first phase of activity began approximately four million years ago with the eruption of lava and ash, such as plagioclase
-hypersthene
-hornblende
-phyric dacite
flows, tephra
, and pyroclastic
breccia
, and concluded with the formation of a central lava dome
which develop the present summit spires of Mount Cayley.
Aggluinated vent breccia
, enormous lava, and welded breccia with plagioclase
-hypersthene
-hornblende
-biotite
-phyric dacite erupted throughout Cayley's second phase of activity, forming the largest of a number of small pinnacle
s extending from the jagged summit ridge of Pyroclastic Peak
called Vulcan's Thumb
on the southwestern flank of Mount Cayley about 600,000 years ago.
Lengthy erosion, which removed nearly all of the original outer cone of pyroclastic
material, was followed by the eruption of satellitic vents
. This third and final phase of activity began about 300,000 years ago with the eruption of a dacite lava flow into the extant valley of Shovelnose Creek
and concluded with the construction of two small satellitic plagioclase
-hypersthene
-biotite
-phyric dacite lava domes about 200,000 years ago.
Mount Cayley is one of the eleven Canadian volcanoes associated with recent seismic activity
; the others are Castle Rock
, Mount Edziza
, Mount Garibaldi
, Hoodoo Mountain
, The Volcano
, Crow Lagoon
, Mount Meager
, Wells Gray-Clearwater Volcanic Field
and Nazko Cone
. Seismic data suggests that these volcanoes still contain living magma
plumbing systems, indicating possible future eruptive activity. Although the available data does not allow a clear conclusion, these observations are further indications that some of Canada's volcanoes are potentially active, and that their associated hazards may be significant. The seismic activity correlates both with some of Canada's most youthful volcanoes, and with long-lived volcanic centers with a history of significant explosive behavior, such as Mount Cayley.
Several hot spring
s on Cayley's southwestern flank indicates that magma
tic heat is still present, providing further evidence of continuous volcanic activity. The long history of volcanism in the area, coupled with continued subduction
off the British Columbia Coast
, indicates that volcanism has not yet concluded in the area. Because of this magmatic heat, Mount Cayley has been a target for geothermal exploration. Bottom hole temperatures of 50 °
C
and thermal gradients of less than 100 °C have been measured in shallow boreholes on Cayley's southwest flank.
Mount Cayley is surrounded by smaller volcanic features and volcano
es called satellite cone
s, also known as parasitic cones. These formed due to Cayley's volcanic vent being heavily blocked by cooled and solidified lava, causing magma to force out of the lines of weakness at the side of the volcano, forming a satellite cone. They commonly derive material from the same source as the initial volcano, although it may have its own magma chamber
system. Similar volcanic formations are found elsewhere in the Cascade Volcanic Arc
, including Mount Shasta
in Northern California
, which consists of four overlapping volcanic cones and several satellite cones, including Black Butte
and Shastina
. The small satellite cones at Mount Cayley become progressively younger from south to north, ranging in age from Pliocene
-to-Pleistocene
which forms a volcanic field
. Because these features are related to the stratovolcano
of Mount Cayley, the volcanic field is commonly referred to as the Mount Cayley volcanic field. The high elevations of the volcanic field, coupled with its cluster of mostly high altitude, non-overlapping vents, have resulted in several eruptions under the Powder Mountain Icefield
, creating many ice-contact features. Due to the volcanic field's remoteness, it has not been studied or mapped in detail. As a result, the number and age of eruptions remains unknown.
Ember Ridge
, the oldest and southern known parasitic vent, is a subglacial volcano
that formed and last erupted during the Pliocene period. It comprises a chain of steep-sided lava dome
s with glassy, tortuously jointed lava, such as hornblende
-phyric basalt
.
Mount Fee
, about 1 kilometre (0.621372736649807 mi) north of Ember Ridge, is a parasitic volcanic plug
comprising a narrow summit ridge about a kilometre (⅔ mi) long. It contains several spines reaching heights of 100 to 150 m (328.1 to 492.1 ). Several pyroclastic deposits are found at the volcano, indicating it might have been covered by layers of pyroclastic rock
s that have now been mostly worn away by erosion. The complete denudation of the central spine as well as the absence of till under lava and pyroclastics indicate it is preglacial or Pleistocene
age.
North of Mount Cayley lies the parasitic Pali Dome
subglacial volcano which is partly covered by glacial ice. It formed and last erupted during the Pleistocene
period, producing coarsely lava flows, such as plagioclase
-hypersthene
-hornblende
-phyric andesite
. Proximal sections of lava flows contain vertical, well developed, large-diameter columnar joints, and lie beneath scoria
eous oxidized flow breccia, suggesting a possible subaerial origin. Distal sections of lava flows are glassy and contain minor diameter columnar joints with horizontal or nearby radiating orientations. Lava flow terminations appear as subvertical cliff
s up to 200 metres (656.2 ft) in height, which are structures constant with eruptions against glacial ice.
Northwest of Pail Dome lies a parasitic subglacial volcano called Cauldron Dome
which also formed and last erupted during the Pleistocene
period. It consists of coarsely lava flows, such as plagioclase
-orthophyroxene-phyric andesite
. Its total geomorphology
is comparable to that of a tuya
. However, any precise record of volcanic glass
or fine-scale jointing has probably been worn away by erosion. Two compositionally identical lava flows spread to the southwest from the base of the volcano. It is likely that Cauldron Dome was formed subglacially and the associated lava flows were erupted within a meltwater conduit.
Slag Hill
, another parasitic subglacial volcano located just north of Mount Cayley, was erupted during the Pleistocene
period, producing glassy lava flows, such as augite
-phyric basaltic andesite
. These lava flows were cooled to form steep-sided, glassy, finely jointed lava domes comparable to those found at Ember Ridge
, and one minor, flat-topped bluff
.
Ring Mountain, just north of Slag Hill, is a parasitic tuya
composed of plagioclase
-hypersthene
-phyric andesite
. The highest elevation of the volcano comprises bomb-like fragments of vesicular, oxidized lava, suggesting that the higher elevation lava flows were most likely subaerial. However, as is the case at volcanoes of comparable morphology elsewhere, lower elevations might have erupted subglacially.
Little Ring Mountain, also known as Little Ring Peak, is an almost circular, flat-topped, steep-sided volcanic feature about 270 metres (885.8 ft) in height and 120 metres (393.7 ft) wide on its top surface. It is known to be the northernmost parasitic cone and is similar in structure to a flat-topped, steep-sided tuya
, although its inner stratigraphy
is not yet known because the area has not been studied in detail due to its remoteness.
Volcanic eruptions in Canada rarely cause fatalities because of their remoteness and low level of activity. The only known fatality due to volcanic activity in Canada occurred at the Tseax Cone
in 1775, when a 22.5 kilometres (14 mi) long basalt
ic lava flow traveled down the Tseax
and Nass River
s, destroying a Nisga'a
village and killing approximately 2,000 people by volcanic gas
es. Many towns and cities near Mount Cayley are home to well over half of British Columbia's human population, and there is a likelihood that future eruptions will cause damage to populated areas, making Mount Cayley and other Garibaldi belt volcanoes a major hazard. There are significant hazards from Canadian volcanoes that require hazard maps and emergency plains. Volcanoes which exhibit significant seismic activity, such as Mount Cayley, appear to be most likely to erupt. A significant eruption of the Garibaldi belt volcanoes would significantly impact Highway 99 and communities like Pemberton
, Whistler
and Squamish
, and possibly Vancouver
.
s exist high up on the western flank of the mountain. There have been shallow earthquakes close to Mount Cayley since 1985, and seismic studies by seismologists
and related geoscientist
s have discovered a strong mid-crustal reflector below it consistent with an unusually large, solidified, mafic
, sill
-like intrusion
lying approximately 12.5 to 13 km (7.8 to 8.1 ) below the mountain. The eruptive scenario is based on past volcanic activity in the Garibaldi Volcanic Belt
, in terms of magnitude and sequence of events, to its neighbor Mount Meager
about 2,350 years ago. This volcanic eruption was similar in size to the 1980 eruption of Mount St. Helens
and is Canada's most recent major eruption.
Significant indicator activity would be expected below the mountain weeks to years before magma penetrates its way through the Earth's
crust
. The large amount of seismicity and the sensitivity of the current seismograph
in this region would warn the Geological Survey of Canada and would most likely cause an expanded monitoring effort. As the magma rises to the surface, the mountain would probably swell and the surface would likely rupture, causing greatly increased vigour in the hot springs, and the formation of new hot springs or fumarole
s on the mountainside. In other words, they would get hotter. Minor and possibly large landslides could occur and may perhaps temporarily dam the Squamish River
, as happened in the past without earthquake shaking and intrusion
-related deformation. The continued presence of magma near the surface would eventually make contact with surface water, causing phreatic eruption
s and debris flows, such as what occurred in the 1980 eruption of Mount St. Helens
. By this time Highway 99 would be closed and Squamish would be at least partially, and possibly entirely, abandoned.
Eruptive activity itself could continue for years, followed by years of decreasing secondary activity. Volcanic ash
would most likely spread throughout the Pacific Northwest
, causing airports to be closed and relevant flights to be diverted or cancelled. The associated ash column
would then extend eastward by the prevailing winds and disrupt air traffic throughout Canada from Alberta
to Newfoundland and Labrador
. The cooling lava would discontinuously spall units to create pyroclastic flow
s (super-heated mix of gas
, ash, and pumice
). The loose volcanic rock and pyroclastic material on Cayley's flanks and in valleys would be periodically reactivated into debris flow
s. Considerable structural improvements would have to be made to reclaim use of Highway 99 and Squamish area.
Currently Mount Cayley is not monitored closely enough by the Geological Survey of Canada to ascertain how active the volcano's magma system is. The existing network of seismographs
has been established to monitor tectonic earthquakes and is too far away to provide a good indication of what is happening beneath the mountain. It may sense an increase in activity if the volcano becomes very restless, but this may only provide warning of a large eruption. It might detect activity only once the volcano has started erupting.
A possible way to detect an eruption is studying Cayley's geological history since every volcano has its own pattern of behavior, in terms of its eruption style, magnitude and frequency, so that its future eruption is expected to be similar to its previous eruptions.
While there is a likelihood of Canada being critically effected by local or close by volcanic eruptions argues that some kind of improvement program is required. Cost-benefit thoughts are critical to dealing with natural hazards. However, a cost-benefit examination needs correct data about the hazard types, magnitudes and occurrences. These do not exist for volcanoes in British Columbia or elsewhere in Canada in the detail required.
Other volcanic techniques, such as hazard mapping, displays a volcano's eruptive history in detail and speculates an understanding of the hazardous activity that could possibly be expected in the future. At present no hazard maps have been created for Mount Cayley because the level of knowledge is insufficient due to its remoteness. A large volcanic hazard program has never existed within the Geological Survey of Canada. The majority of information has been collected in a lengthy, separate way from the support of several employees, such as volcanologist
s and other geologic scientist
s. Current knowledge is best established at Mount Meager
just north of Mount Cayley and is likely to rise considerably with a temporary mapping and monitoring project. Knowledge at Mount Cayley and other volcanoes in the Garibaldi Volcanic Belt is not as established, but certain contributions are being done at least Mount Cayley. An intensive program classifying infrastructural exposure near young Canadian volcanoes and quick hazard assessment at each individual volcanic edifice associated with recent seismic activity would be in advance and would produce a quick and productive determination of priority areas for further efforts.
The existing network of seismographs to monitor tectonic earthquakes has existed since 1975, although it remained small in population until 1985. Apart from a few short-term seismic monitoring experiments by the Geological Survey of Canada, no volcano monitoring has been accomplished at Mount Cayley or at other volcanoes in Canada at a level approaching that in other established countries with historically active volcanoes. Active or restless volcanoes are usually monitored using at least three seismographs within approximately 15 kilometres (9.3 mi), and frequently within 5 kilometres (3 mi), for better sensitivity of detection and reduced location errors, particularly for earthquake depth. Such monitoring detects the risk of an eruption, offering a forecasting capability which is important to mitigating volcanic risk. Currently Mount Cayley does not have a seismograph closer than 41 kilometres (25.5 mi). With increasing distance and declining numbers of seismographs used to indicate seismic activity, the prediction capability is reduced because earthquake location accuracy and depth decreases, and the network becomes not as accurate. The inaccurate earthquake locations in the Garibaldi Volcanic Belt are a few kilometers, and in more isolated northern regions they are up to 10 kilometres (6 mi). The location magnitude level in the Garibaldi Volcanic Belt is about magnitude 1 to 1.5, and elsewhere it is magnitude 1.5 to 2. At carefully monitored volcanoes both the located and noticed events are recorded and surveyed immediately to improve the understanding of a future eruption. Undetected events are not recorded or surveyed in British Columbia immediately, nor in an easy-to-access process.
In countries like Canada it is possible that small precursor swarms might go undetected, particularly if no events were observed; more significant events in larger swarms would be detected but only a minor subdivision of the swarm events would be complex to clarify them with confidence as volcanic in nature, or even associate them with an individual volcanic edifice.
Stratovolcano
A stratovolcano, also known as a composite volcano, is a tall, conical volcano built up by many layers of hardened lava, tephra, pumice, and volcanic ash. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile and periodic, explosive eruptions...
in Squamish-Lillooet Regional District of southwestern British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
. Located 45 kilometres (28 mi) north of Squamish
Squamish, British Columbia
Squamish is a community and a district municipality in the Canadian province of British Columbia, located at the north end of Howe Sound on the Sea to Sky Highway...
and 24 kilometres (14.9 mi) west of Whistler
Whistler, British Columbia
Whistler is a Canadian resort town in the southern Pacific Ranges of the Coast Mountains in the province of British Columbia, Canada, approximately north of Vancouver...
in the Pacific Ranges
Pacific Ranges
The Pacific Ranges are the southernmost subdivision of the Coast Mountains portion of the Pacific Cordillera. Located entirely within British Columbia, Canada, they run northwest from the lower stretches of the Fraser River to Bella Coola, north of which are the Kitimat Ranges.The Pacific Ranges...
of the Coast Mountains
Coast Mountains
The Coast Mountains are a major mountain range, in the Pacific Coast Ranges, of western North America, extending from southwestern Yukon through the Alaska Panhandle and virtually all of the Coast of British Columbia. They are so-named because of their proximity to the sea coast, and are often...
, it rises 2264 metres (7,427.8 ft) above the Squamish River
Squamish River
The Squamish River is a short but very large river in the Canadian province of British Columbia. Its drainage basin is in size. The total length of the Squamish River is approximately .-Course:...
to the west and 1844 metres (6,049.9 ft) above the Cheakamus River
Cheakamus River
The Cheakamus River is a tributary of the Squamish River, beginning on the west slopes of Outlier Peak in Garibaldi Provincial Park upstream from Cheakamus Lake on the southeastern outskirts of the resort area of Whistler. The river flows into Cheakamus Lake before exiting it and flowing...
to the east.
Mount Cayley consists of ridge
Ridge
A ridge is a geological feature consisting of a chain of mountains or hills that form a continuous elevated crest for some distance. Ridges are usually termed hills or mountains as well, depending on size. There are several main types of ridges:...
s, rounded lava dome
Lava dome
|250px|thumb|right|Image of the [[rhyolitic]] lava dome of [[Chaitén Volcano]] during its 2008–2009 eruption.In volcanology, a lava dome is a roughly circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano...
s and sharp eroded rocky pinnacle
Pinnacle
A pinnacle is an architectural ornament originally forming the cap or crown of a buttress or small turret, but afterwards used on parapets at the corners of towers and in many other situations. The pinnacle looks like a small spire...
s with the highest reaching 2377 metres (7,798.6 ft) in elevation. It lies at the southern end of a field of glacial
Glacier
A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...
ice called the Powder Mountain Icefield
Powder Mountain Icefield
The Powder Mountain Icefield, also called the Powder Mountain Icecap and the Cayley Icefield, is a glacial field in the Pacific Ranges of southwestern British Columbia, Canada, about west of Whistler and about north of Vancouver...
.
Human history
To the Squamish, the local indigenous peopleIndigenous peoples of the Pacific Northwest Coast
The Indigenous peoples of the Pacific Northwest Coast are the pre-Columbian inhabitants of the Pacific Northwest Coast, their descendants, and many ethnic groups who identify with those historical peoples. They are now situated within the Canadian Province of British Columbia and the U.S...
of this territory, the mountain is called t'ak'takmu'yin tl'a in7in'a'xe7en. In their language it means "Landing Place of the Thunderbird". This name of the mountain refers to the legendary Thunderbird
Thunderbird (mythology)
The Thunderbird is a legendary creature in certain North American indigenous peoples' history and culture. It is considered a "supernatural" bird of power and strength...
, a creature in North American indigenous peoples' history and culture. Like Black Tusk
Black Tusk
Black Tusk is a remarkably abrupt pinnacle of volcanic rock located in Garibaldi Provincial Park of British Columbia, Canada. At above sea level, the upper spire is visible from a great distance in all directions. It is particularly noticeable from the Sea-to-Sky Highway just south of Whistler,...
further south, the rock was said to have been burnt black by the Thunderbird's lightning. This mountain, like others located in the area, is considered sacred because it plays an important part in their history.
The first recorded ascent of Mount Cayley was made by the mountaineers E.C. Brooks, W.G. Wheatley, B.Clegg, R.E. Knight, and Tom Fyles in 1928. During this time, the party named the volcano after the late Beverley Cochrane Cayley, who was an ardent mountaineer of the executive committees of the British Columbia Mountaineering Club
British Columbia Mountaineering Club
The British Columbia Mountaineering Club is a mountaineering organization, based in Vancouver, British Columbia. Founded on October 28, 1907 as the Vancouver Mountaineering Club, it became one of the centres of Canadian Mountaineering, particularly in the Coast Mountains of British Columbia...
and the Vancouver
Vancouver
Vancouver is a coastal seaport city on the mainland of British Columbia, Canada. It is the hub of Greater Vancouver, which, with over 2.3 million residents, is the third most populous metropolitan area in the country,...
section of the Alpine Club
Alpine Club of Canada
The Alpine Club of Canada is a mountain club with a National Office in Canmore, Alberta that has been a focal point for Canadian mountaineering since its founding in 1906. The club was co-founded by Arthur Oliver Wheeler, who served as its first president, and Elizabeth Parker, a journalist for...
for several years. Beverley Cayley was a friend of those in the climbing party, and died on June 8, 1928 at the age of 29 in Vancouver. Photographs of Mount Cayley were published in the Canadian Alpine Journal Vol XX in 1931.
Geology
Like other volcanoes in southwestern British Columbia, Mount Cayley lies within the Coast Plutonic Complex, which is the single largest contiguous graniteGranite
Granite is a common and widely occurring type of intrusive, felsic, igneous rock. Granite usually has a medium- to coarse-grained texture. Occasionally some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic...
outcropping in North America. The intrusive
Intrusion
An intrusion is liquid rock that forms under Earth's surface. Magma from under the surface is slowly pushed up from deep within the earth into any cracks or spaces it can find, sometimes pushing existing country rock out of the way, a process that can take millions of years. As the rock slowly...
and metamorphic rock
Metamorphic rock
Metamorphic rock is the transformation of an existing rock type, the protolith, in a process called metamorphism, which means "change in form". The protolith is subjected to heat and pressure causing profound physical and/or chemical change...
s of the Coast Plutonic Complex extend approximately 1800 kilometres (1,118.5 mi) along the coast of British Columbia, the Alaska Panhandle
Alaska Panhandle
Southeast Alaska, sometimes referred to as the Alaska Panhandle, is the southeastern portion of the U.S. state of Alaska, which lies west of the northern half of the Canadian province of British Columbia. The majority of Southeast Alaska's area is part of the Tongass National Forest, the United...
and southwestern Yukon
Yukon
Yukon is the westernmost and smallest of Canada's three federal territories. It was named after the Yukon River. The word Yukon means "Great River" in Gwich’in....
. This is a remnant of a once vast volcanic arc
Volcanic arc
A volcanic arc is a chain of volcanoes positioned in an arc shape as seen from above. Offshore volcanoes form islands, resulting in a volcanic island arc. Generally they result from the subduction of an oceanic tectonic plate under another tectonic plate, and often parallel an oceanic trench...
called the Coast Range Arc that formed as a result of subduction
Subduction
In geology, subduction is the process that takes place at convergent boundaries by which one tectonic plate moves under another tectonic plate, sinking into the Earth's mantle, as the plates converge. These 3D regions of mantle downwellings are known as "Subduction Zones"...
of the Farallon
Farallon Plate
The Farallon Plate was an ancient oceanic plate, which began subducting under the west coast of the North American Plate— then located in modern Utah— as Pangaea broke apart during the Jurassic Period...
and Kula Plate
Kula Plate
The Kula Plate is an oceanic tectonic plate under the northern Pacific Ocean south of the Near Islands segment of the Aleutian Islands. It is subducting under the North American Plate at the Aleutian Trench and is surrounded by the Pacific Plate...
s during the Jurassic
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
-to-Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
periods. In contrast, Mount Cayley, Mount Meager
Mount Meager
Mount Meager, originally known as Meager Mountain, is a complex volcano in the Sea-to-Sky Corridor of southwestern British Columbia, Canada. It is located north of Vancouver at the northern end of the Pemberton Valley. Part of the Cascade Volcanic Arc of western North America, its summit is above...
, Mount Garibaldi
Mount Garibaldi
Mount Garibaldi is a potentially active stratovolcano in the Sea to Sky Country of British Columbia, north of Vancouver, Canada. Located in the southernmost Coast Mountains, it is one of the most recognized peaks in the South Coast region, as well as British Columbia's best known volcano...
and Silverthrone Caldera
Silverthrone Caldera
The Silverthrone Caldera is a potentially active caldera complex in southwestern British Columbia, Canada, located over northwest of the city of Vancouver and about west of Mount Waddington in the Pacific Ranges of the Coast Mountains. The caldera is one of the largest of the few calderas in...
are of recent volcanic origin.
Mount Cayley consists mostly of an igneous rock
Igneous rock
Igneous rock is one of the three main rock types, the others being sedimentary and metamorphic rock. Igneous rock is formed through the cooling and solidification of magma or lava...
with a high iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
content called dacite
Dacite
Dacite is an igneous, volcanic rock. It has an aphanitic to porphyritic texture and is intermediate in composition between andesite and rhyolite. The relative proportions of feldspars and quartz in dacite, and in many other volcanic rocks, are illustrated in the QAPF diagram...
, although another igneous rock, rhyodacite
Rhyodacite
Rhyodacite is an extrusive volcanic rock intermediate in composition between dacite and rhyolite. It is the extrusive equivalent of granodiorite. Phenocrysts of sodium rich plagioclase, sanidine, quartz, and biotite or hornblende are typically set in an aphanitic to glassy light to intermediate...
, with intermediate composition of dacite and rhyolite
Rhyolite
This page is about a volcanic rock. For the ghost town see Rhyolite, Nevada, and for the satellite system, see Rhyolite/Aquacade.Rhyolite is an igneous, volcanic rock, of felsic composition . It may have any texture from glassy to aphanitic to porphyritic...
is also present. Unlike many of the other volcanoes further south, Cayley does not dominate the surrounding landscape, which consists of high, rugged peaks.
Origins
Cascadia subduction zone
The Cascadia subduction zone is a subduction zone, a type of convergent plate boundary that stretches from northern Vancouver Island to northern California. It is a very long sloping fault that separates the Juan de Fuca and North America plates.New ocean floor is being created offshore of...
—a long convergent plate boundary that stretches from mid-Vancouver Island
Vancouver Island
Vancouver Island is a large island in British Columbia, Canada. It is one of several North American locations named after George Vancouver, the British Royal Navy officer who explored the Pacific Northwest coast of North America between 1791 and 1794...
to Northern California
Northern California
Northern California is the northern portion of the U.S. state of California. The San Francisco Bay Area , and Sacramento as well as its metropolitan area are the main population centers...
. The subduction zone separates the Juan de Fuca
Juan de Fuca Plate
The Juan de Fuca Plate, named after the explorer of the same name, is a tectonic plate, generated from the Juan de Fuca Ridge, and subducting under the northerly portion of the western side of the North American Plate at the Cascadia subduction zone...
, Explorer
Explorer Plate
The Explorer Plate is an oceanic tectonic plate beneath the Pacific Ocean off the west coast of Vancouver Island, Canada.The eastern boundary of the Explorer Plate is being slowly subducted under the North American Plate, to which it may eventually accrete owing to the slow rate of subduction...
, Gorda
Gorda Plate
The Gorda Plate, located beneath the Pacific Ocean off the coast of northern California, is one of the northern remnants of the Farallon Plate. It is sometimes referred to as simply the southernmost portion of the neighboring Juan de Fuca Plate, another Farallon remnant.Unlike most tectonic...
and North American Plate
North American Plate
The North American Plate is a tectonic plate covering most of North America, Greenland, Cuba, Bahamas, and parts of Siberia, Japan and Iceland. It extends eastward to the Mid-Atlantic Ridge and westward to the Chersky Range in eastern Siberia. The plate includes both continental and oceanic crust...
s. Here, the oceanic crust
Oceanic crust
Oceanic crust is the part of Earth's lithosphere that surfaces in the ocean basins. Oceanic crust is primarily composed of mafic rocks, or sima, which is rich in iron and magnesium...
of the Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
sinks beneath North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
at a rate of 40 millimetres (1.6 in) per year. Hot magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...
upwelling above the descending oceanic plate creates volcanoes, and each individual volcano erupts for a few million years. These volcanoes are commonly referred to as Cascade volcanoes because they were formed by Cascadia
Cascadia
Cascadia, a term that derives from the Cascade Range, may refer to:* the Pacific Northwest* Cascadia, a former plant genus now included in Saxifraga* 1700 Cascadia earthquake...
subduction
Subduction
In geology, subduction is the process that takes place at convergent boundaries by which one tectonic plate moves under another tectonic plate, sinking into the Earth's mantle, as the plates converge. These 3D regions of mantle downwellings are known as "Subduction Zones"...
.
The subduction zone has existed for at least 37 million years, and has created a line of volcanoes called the Cascade Volcanic Arc which stretches over 1000 kilometres (621.4 mi) along the subduction zone. Several volcanoes in the arc are potentially active. Lassen Peak
Lassen Peak
Lassen Peak is the southernmost active volcano in the Cascade Range. It is part of the Cascade Volcanic Arc which is an arc that stretches from northern California to southwestern British Columbia...
in California, which last erupted in 1917, is the southernmost historically active volcano in the arc, and Mount Meager
Mount Meager
Mount Meager, originally known as Meager Mountain, is a complex volcano in the Sea-to-Sky Corridor of southwestern British Columbia, Canada. It is located north of Vancouver at the northern end of the Pemberton Valley. Part of the Cascade Volcanic Arc of western North America, its summit is above...
, just north of Mount Cayley, which erupted about 2,350 years ago, is generally considered the northernmost. A few isolated volcanic centers northwest of Mount Meager, such as the Silverthrone Caldera
Silverthrone Caldera
The Silverthrone Caldera is a potentially active caldera complex in southwestern British Columbia, Canada, located over northwest of the city of Vancouver and about west of Mount Waddington in the Pacific Ranges of the Coast Mountains. The caldera is one of the largest of the few calderas in...
, which is a 20 kilometres (12.4 mi) wide, deeply dissected caldera
Caldera
A caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption, such as the one at Yellowstone National Park in the US. They are sometimes confused with volcanic craters...
complex, are considered by some geologists to be the northernmost member of the arc.
Structure
Garibaldi Volcanic Belt
The Garibaldi Volcanic Belt, also called the Canadian Cascade Arc, is a northwest-southeast trending volcanic chain in the Pacific Ranges of the Coast Mountains that extends from Watts Point in the south to the Ha-Iltzuk Icefield in the north. This chain of volcanoes is located in southwestern...
. Like other stratovolcano
Stratovolcano
A stratovolcano, also known as a composite volcano, is a tall, conical volcano built up by many layers of hardened lava, tephra, pumice, and volcanic ash. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile and periodic, explosive eruptions...
es, it is composed of layers of hardened lava, tephra
Tephra
200px|thumb|right|Tephra horizons in south-central [[Iceland]]. The thick and light coloured layer at center of the photo is [[rhyolitic]] tephra from [[Hekla]]....
, and volcanic ash. Eruptions are explosive in nature, involving viscous magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...
, glowing avalanches of hot volcanic ash
Volcanic ash
Volcanic ash consists of small tephra, which are bits of pulverized rock and glass created by volcanic eruptions, less than in diameter. There are three mechanisms of volcanic ash formation: gas release under decompression causing magmatic eruptions; thermal contraction from chilling on contact...
and pyroclastic flow
Pyroclastic flow
A pyroclastic flow is a fast-moving current of superheated gas and rock , which reaches speeds moving away from a volcano of up to 700 km/h . The flows normally hug the ground and travel downhill, or spread laterally under gravity...
s. The source magma of this rock is classified as acid
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...
ic, having high to intermediate levels of silica (as in rhyolite
Rhyolite
This page is about a volcanic rock. For the ghost town see Rhyolite, Nevada, and for the satellite system, see Rhyolite/Aquacade.Rhyolite is an igneous, volcanic rock, of felsic composition . It may have any texture from glassy to aphanitic to porphyritic...
, dacite
Dacite
Dacite is an igneous, volcanic rock. It has an aphanitic to porphyritic texture and is intermediate in composition between andesite and rhyolite. The relative proportions of feldspars and quartz in dacite, and in many other volcanic rocks, are illustrated in the QAPF diagram...
, or andesite
Andesite
Andesite is an extrusive igneous, volcanic rock, of intermediate composition, with aphanitic to porphyritic texture. In a general sense, it is the intermediate type between basalt and dacite. The mineral assemblage is typically dominated by plagioclase plus pyroxene and/or hornblende. Magnetite,...
).
Stratovolcanoes are a common feature of subduction zones. The magma that forms them arises when water, which is trapped both in hydrated minerals and in the porous basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
rock of the upper oceanic crust, is released into mantle
Mantle (geology)
The mantle is a part of a terrestrial planet or other rocky body large enough to have differentiation by density. The interior of the Earth, similar to the other terrestrial planets, is chemically divided into layers. The mantle is a highly viscous layer between the crust and the outer core....
rock of the asthenosphere
Asthenosphere
The asthenosphere is the highly viscous, mechanically weak and ductilely-deforming region of the upper mantle of the Earth...
above the sinking oceanic slab. The release of water from hydrated minerals is termed "dewatering", and occurs at specific pressure/temperature conditions for specific minerals as the plate subducts to lower depths. The water freed from the subducting slab lowers the melting point
Melting point
The melting point of a solid is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at standard atmospheric pressure...
of the overlying mantle rock, which then undergoes partial melting and rises due to its density relative to the surrounding mantle rock, and pools temporarily at the base of the lithosphere
Lithosphere
The lithosphere is the rigid outermost shell of a rocky planet. On Earth, it comprises the crust and the portion of the upper mantle that behaves elastically on time scales of thousands of years or greater.- Earth's lithosphere :...
. The magma then rises through the crust
Crust (geology)
In geology, the crust is the outermost solid shell of a rocky planet or natural satellite, which is chemically distinct from the underlying mantle...
, incorporating silica rich crustal rock, leading to a final intermediate composition. When the magma nears the surface it pools in a magma chamber
Magma chamber
A magma chamber is a large underground pool of molten rock found beneath the surface of the Earth. The molten rock in such a chamber is under great pressure, and given enough time, that pressure can gradually fracture the rock around it creating outlets for the magma...
under the volcano. The relatively low pressure of the magma allows water and other volatiles
Volatility (chemistry)
In chemistry and physics, volatility is the tendency of a substance to vaporize. Volatility is directly related to a substance's vapor pressure. At a given temperature, a substance with higher vapor pressure vaporizes more readily than a substance with a lower vapor pressure.The term is primarily...
(CO2, S2-, Cl-) dissolved in the magma to begin to come out of solution, much like when a bottle of carbonated water
Carbonated water
Carbonated water is water into which carbon dioxide gas under pressure has been dissolved, a process that causes the water to become effervescent....
is opened. Once a critical volume of magma and gas accumulates, the obstacle provided by the volcanic cone
Volcanic cone
Volcanic cones are among the simplest volcanic formations. They are built by ejecta from a volcanic vent, piling up around the vent in the shape of a cone with a central crater. Volcanic cones are of different types, depending upon the nature and size of the fragments ejected during the eruption...
is overcome, leading to a sudden explosive eruption
Explosive eruption
An explosive eruption is a volcanic term to describe a violent, explosive type of eruption. Mount St. Helens in 1980 was an example. Such an eruption is driven by gas accumulating under great pressure. Driven by hot rising magma, it interacts with ground water until the pressure increases to the...
.
Eruptive history
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
time compared to most other Cascade volcanoes, which were formed in the past two million years, and mostly in the past one million years or less. Cayley's first phase of activity began approximately four million years ago with the eruption of lava and ash, such as plagioclase
Plagioclase
Plagioclase is an important series of tectosilicate minerals within the feldspar family. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a solid solution series, more properly known as the plagioclase feldspar series...
-hypersthene
Hypersthene
Hypersthene is a common rock-forming inosilicate mineral belonging to the group of orthorhombic pyroxenes. Many references have formally abandoned this term, preferring to categorise this mineral as enstatite or ferrosilite. It is found in igneous and some metamorphic rocks as well as in stony and...
-hornblende
Hornblende
Hornblende is a complex inosilicate series of minerals .It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole....
-phyric dacite
Dacite
Dacite is an igneous, volcanic rock. It has an aphanitic to porphyritic texture and is intermediate in composition between andesite and rhyolite. The relative proportions of feldspars and quartz in dacite, and in many other volcanic rocks, are illustrated in the QAPF diagram...
flows, tephra
Tephra
200px|thumb|right|Tephra horizons in south-central [[Iceland]]. The thick and light coloured layer at center of the photo is [[rhyolitic]] tephra from [[Hekla]]....
, and pyroclastic
Pyroclastic rock
Pyroclastic rocks or pyroclastics are clastic rocks composed solely or primarily of volcanic materials. Where the volcanic material has been transported and reworked through mechanical action, such as by wind or water, these rocks are termed volcaniclastic...
breccia
Breccia
Breccia is a rock composed of broken fragments of minerals or rock cemented together by a fine-grained matrix, that can be either similar to or different from the composition of the fragments....
, and concluded with the formation of a central lava dome
Lava dome
|250px|thumb|right|Image of the [[rhyolitic]] lava dome of [[Chaitén Volcano]] during its 2008–2009 eruption.In volcanology, a lava dome is a roughly circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano...
which develop the present summit spires of Mount Cayley.
Aggluinated vent breccia
Breccia
Breccia is a rock composed of broken fragments of minerals or rock cemented together by a fine-grained matrix, that can be either similar to or different from the composition of the fragments....
, enormous lava, and welded breccia with plagioclase
Plagioclase
Plagioclase is an important series of tectosilicate minerals within the feldspar family. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a solid solution series, more properly known as the plagioclase feldspar series...
-hypersthene
Hypersthene
Hypersthene is a common rock-forming inosilicate mineral belonging to the group of orthorhombic pyroxenes. Many references have formally abandoned this term, preferring to categorise this mineral as enstatite or ferrosilite. It is found in igneous and some metamorphic rocks as well as in stony and...
-hornblende
Hornblende
Hornblende is a complex inosilicate series of minerals .It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole....
-biotite
Biotite
Biotite is a common phyllosilicate mineral within the mica group, with the approximate chemical formula . More generally, it refers to the dark mica series, primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more aluminous endmembers...
-phyric dacite erupted throughout Cayley's second phase of activity, forming the largest of a number of small pinnacle
Pinnacle
A pinnacle is an architectural ornament originally forming the cap or crown of a buttress or small turret, but afterwards used on parapets at the corners of towers and in many other situations. The pinnacle looks like a small spire...
s extending from the jagged summit ridge of Pyroclastic Peak
Pyroclastic Peak
Pyroclastic Peak is the second highest of the five named volcanic peaks immediately south of Mount Cayley in British Columbia, Canada. It is steep and rotten and is located southwest of Callaghan Lake and west of Whistler...
called Vulcan's Thumb
Vulcan's Thumb
Vulcan's Thumb is a deeply dissected, unstable stratovolcano located directly on the southern ridge of Pyroclastic Peak. It is one of the five main volcanic peaks of the Mount Cayley massif and remains unclimbed because of technical difficulties and its loose rock...
on the southwestern flank of Mount Cayley about 600,000 years ago.
Lengthy erosion, which removed nearly all of the original outer cone of pyroclastic
Pyroclastic rock
Pyroclastic rocks or pyroclastics are clastic rocks composed solely or primarily of volcanic materials. Where the volcanic material has been transported and reworked through mechanical action, such as by wind or water, these rocks are termed volcaniclastic...
material, was followed by the eruption of satellitic vents
Satellite cone
A parasitic cone is the cone-shaped accumulation of volcanic material not part of the central vent of a volcano. One forms by eruptions from fractures on the flank of the volcano. These fractures occur because of the flank of the volcano is unstable...
. This third and final phase of activity began about 300,000 years ago with the eruption of a dacite lava flow into the extant valley of Shovelnose Creek
Shovelnose Creek
Shovelnose Creek is a creek in the Pacific Ranges of the Coast Mountains in southwestern British Columbia, Canada. It flows southwest into the Squamish River and south of the Elaho River....
and concluded with the construction of two small satellitic plagioclase
Plagioclase
Plagioclase is an important series of tectosilicate minerals within the feldspar family. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a solid solution series, more properly known as the plagioclase feldspar series...
-hypersthene
Hypersthene
Hypersthene is a common rock-forming inosilicate mineral belonging to the group of orthorhombic pyroxenes. Many references have formally abandoned this term, preferring to categorise this mineral as enstatite or ferrosilite. It is found in igneous and some metamorphic rocks as well as in stony and...
-biotite
Biotite
Biotite is a common phyllosilicate mineral within the mica group, with the approximate chemical formula . More generally, it refers to the dark mica series, primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more aluminous endmembers...
-phyric dacite lava domes about 200,000 years ago.
Current activity
Seismology
Seismology is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other planet-like bodies. The field also includes studies of earthquake effects, such as tsunamis as well as diverse seismic sources such as volcanic, tectonic, oceanic,...
; the others are Castle Rock
Castle Rock (volcano)
Castle Rock is a volcanic neck located west of Iskut and 8 km northwest of Tuktsayda Mountain in British Columbia, Canada. It is part of the Pacific Ring of Fire that includes over 160 active volcanoes and is in the Klastline Group, Northern Cordilleran Volcanic Province and last erupted in...
, Mount Edziza
Mount Edziza
Mount Edziza is a stratovolcano in the Stikine Country of northwestern British Columbia, Canada. The volcano and the surrounding area are protected within Mount Edziza Provincial Park. It consists of a complex of multiple peaks and ridges, with several glaciers flowing in all directions. The summit...
, Mount Garibaldi
Mount Garibaldi
Mount Garibaldi is a potentially active stratovolcano in the Sea to Sky Country of British Columbia, north of Vancouver, Canada. Located in the southernmost Coast Mountains, it is one of the most recognized peaks in the South Coast region, as well as British Columbia's best known volcano...
, Hoodoo Mountain
Hoodoo Mountain
Hoodoo Mountain is a potentially active flat-topped stratovolcano in the Stikine Country of northwestern British Columbia, Canada, located northeast of Wrangell, Alaska on the north side of the lower Iskut River and east of its junction with the Stikine River...
, The Volcano
The Volcano (British Columbia)
The Volcano, also known as Lava Fork volcano, is a small cinder cone in the Boundary Ranges of the Coast Mountains in northwestern British Columbia, Canada. It is located approximately northwest of the small community of Stewart near the head of Lava Fork...
, Crow Lagoon
Crow Lagoon
Crow Lagoon is a little-known volcanic center located north of Prince Rupert, British Columbia, Canada. There are beds of thick, basaltic tephra that are of Holocene age....
, Mount Meager
Mount Meager
Mount Meager, originally known as Meager Mountain, is a complex volcano in the Sea-to-Sky Corridor of southwestern British Columbia, Canada. It is located north of Vancouver at the northern end of the Pemberton Valley. Part of the Cascade Volcanic Arc of western North America, its summit is above...
, Wells Gray-Clearwater Volcanic Field
Wells Gray-Clearwater volcanic field
The Wells Gray-Clearwater volcanic field, also called the Clearwater Cone Group, is a potentially active monogenetic volcanic field in east-central British Columbia, Canada, located approximately north of Kamloops. It is situated in the Cariboo Mountains of the Columbia Mountains and on the...
and Nazko Cone
Nazko Cone
Nazko Cone is a small potentially active basaltic cinder cone in central British Columbia, Canada, located 75 km west of Quesnel and 150 kilometers southwest of Prince George. It is considered the easternmost volcano in the Anahim Volcanic Belt. The small tree-covered cone rises 120 m above...
. Seismic data suggests that these volcanoes still contain living magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...
plumbing systems, indicating possible future eruptive activity. Although the available data does not allow a clear conclusion, these observations are further indications that some of Canada's volcanoes are potentially active, and that their associated hazards may be significant. The seismic activity correlates both with some of Canada's most youthful volcanoes, and with long-lived volcanic centers with a history of significant explosive behavior, such as Mount Cayley.
Several hot spring
Hot spring
A hot spring is a spring that is produced by the emergence of geothermally heated groundwater from the Earth's crust. There are geothermal hot springs in many locations all over the crust of the earth.-Definitions:...
s on Cayley's southwestern flank indicates that magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...
tic heat is still present, providing further evidence of continuous volcanic activity. The long history of volcanism in the area, coupled with continued subduction
Subduction
In geology, subduction is the process that takes place at convergent boundaries by which one tectonic plate moves under another tectonic plate, sinking into the Earth's mantle, as the plates converge. These 3D regions of mantle downwellings are known as "Subduction Zones"...
off the British Columbia Coast
British Columbia Coast
The British Columbia Coast or BC Coast is Canada's western continental coastline on the Pacific Ocean. The usage is synonymous with the term West Coast of Canada....
, indicates that volcanism has not yet concluded in the area. Because of this magmatic heat, Mount Cayley has been a target for geothermal exploration. Bottom hole temperatures of 50 °
Degree (temperature)
The term degree is used in several scales of temperature. The symbol ° is usually used, followed by the initial letter of the unit, for example “°C” for degree Celsius...
C
Celsius
Celsius is a scale and unit of measurement for temperature. It is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...
and thermal gradients of less than 100 °C have been measured in shallow boreholes on Cayley's southwest flank.
Related features
Mount Cayley is surrounded by smaller volcanic features and volcano
Volcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...
es called satellite cone
Satellite cone
A parasitic cone is the cone-shaped accumulation of volcanic material not part of the central vent of a volcano. One forms by eruptions from fractures on the flank of the volcano. These fractures occur because of the flank of the volcano is unstable...
s, also known as parasitic cones. These formed due to Cayley's volcanic vent being heavily blocked by cooled and solidified lava, causing magma to force out of the lines of weakness at the side of the volcano, forming a satellite cone. They commonly derive material from the same source as the initial volcano, although it may have its own magma chamber
Magma chamber
A magma chamber is a large underground pool of molten rock found beneath the surface of the Earth. The molten rock in such a chamber is under great pressure, and given enough time, that pressure can gradually fracture the rock around it creating outlets for the magma...
system. Similar volcanic formations are found elsewhere in the Cascade Volcanic Arc
Cascade Volcanoes
The Cascade Volcanoes are a number of volcanoes in a volcanic arc in western North America, extending from southwestern British Columbia through Washington and Oregon to Northern California, a distance of well over 700 mi ...
, including Mount Shasta
Mount Shasta
Mount Shasta is located at the southern end of the Cascade Range in Siskiyou County, California and at is the second highest peak in the Cascades and the fifth highest in California...
in Northern California
Northern California
Northern California is the northern portion of the U.S. state of California. The San Francisco Bay Area , and Sacramento as well as its metropolitan area are the main population centers...
, which consists of four overlapping volcanic cones and several satellite cones, including Black Butte
Black Butte (Siskiyou County, California)
Black Butte is a cluster of overlapping dacite lava domes in a butte,a parasitic satellite cone of Mount Shasta. It is located directly adjacent to Interstate 5 at milepost 742 between the city of Mount Shasta and Weed, California. The highway crosses a pass, Black Butte Summit, at the western...
and Shastina
Shastina
Shastina is the highest satellite cone of Mount Shasta, and one of four overlapping volcanic cones which together form the most voluminous stratovolcano in the Cascade Range. At , Shastina is taller than Mount Adams and would rank as the third highest volcano in the Cascades behind Mount Rainier...
. The small satellite cones at Mount Cayley become progressively younger from south to north, ranging in age from Pliocene
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
-to-Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
which forms a volcanic field
Volcanic field
A volcanic field is an area of the Earth's crust that is prone to localized volcanic activity. They usually contain 10 to 100 volcanoes, such as cinder cones and are usually in clusters. Lava flows may also occur...
. Because these features are related to the stratovolcano
Stratovolcano
A stratovolcano, also known as a composite volcano, is a tall, conical volcano built up by many layers of hardened lava, tephra, pumice, and volcanic ash. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile and periodic, explosive eruptions...
of Mount Cayley, the volcanic field is commonly referred to as the Mount Cayley volcanic field. The high elevations of the volcanic field, coupled with its cluster of mostly high altitude, non-overlapping vents, have resulted in several eruptions under the Powder Mountain Icefield
Powder Mountain Icefield
The Powder Mountain Icefield, also called the Powder Mountain Icecap and the Cayley Icefield, is a glacial field in the Pacific Ranges of southwestern British Columbia, Canada, about west of Whistler and about north of Vancouver...
, creating many ice-contact features. Due to the volcanic field's remoteness, it has not been studied or mapped in detail. As a result, the number and age of eruptions remains unknown.
Ember Ridge
Ember Ridge
Ember Ridge is a volcanic mountain ridge associated with the Mount Cayley volcanic field in British Columbia, Canada. Ember Ridge is made of a series of steep-sided domes of glassy, complexly jointed, hornblende-phyric basalt with the most recent eruptions during the Holocene...
, the oldest and southern known parasitic vent, is a subglacial volcano
Subglacial volcano
A subglacial volcano, also known as a glaciovolcano, is a volcanic form produced by subglacial eruptions or eruptions beneath the surface of a glacier or ice sheet which is then melted into a lake by the rising lava...
that formed and last erupted during the Pliocene period. It comprises a chain of steep-sided lava dome
Lava dome
|250px|thumb|right|Image of the [[rhyolitic]] lava dome of [[Chaitén Volcano]] during its 2008–2009 eruption.In volcanology, a lava dome is a roughly circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano...
s with glassy, tortuously jointed lava, such as hornblende
Hornblende
Hornblende is a complex inosilicate series of minerals .It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole....
-phyric basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
.
Mount Fee
Mount Fee
Mount Fee is a volcanic peak in the Pacific Ranges of the Coast Mountains in southwestern British Columbia, Canada. It is located south of Callaghan Lake and west of the resort town of Whistler. With a summit elevation of and a topographic prominence of , it rises above the surrounding rugged...
, about 1 kilometre (0.621372736649807 mi) north of Ember Ridge, is a parasitic volcanic plug
Volcanic plug
A volcanic plug, also called a volcanic neck or lava neck, is a volcanic landform created when magma hardens within a vent on an active volcano. When forming, a plug can cause an extreme build-up of pressure if volatile-charged magma is trapped beneath it, and this can sometimes lead to an...
comprising a narrow summit ridge about a kilometre (⅔ mi) long. It contains several spines reaching heights of 100 to 150 m (328.1 to 492.1 ). Several pyroclastic deposits are found at the volcano, indicating it might have been covered by layers of pyroclastic rock
Pyroclastic rock
Pyroclastic rocks or pyroclastics are clastic rocks composed solely or primarily of volcanic materials. Where the volcanic material has been transported and reworked through mechanical action, such as by wind or water, these rocks are termed volcaniclastic...
s that have now been mostly worn away by erosion. The complete denudation of the central spine as well as the absence of till under lava and pyroclastics indicate it is preglacial or Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
age.
North of Mount Cayley lies the parasitic Pali Dome
Pali Dome
Pali Dome is the unofficial name for a volcanic peak in the Pacific Ranges of the Coast Mountains in southwestern British Columbia, Canada.-See also:*List of volcanoes in Canada*Mount Cayley volcanic field*Volcanism of Canada*Volcanism of Western Canada...
subglacial volcano which is partly covered by glacial ice. It formed and last erupted during the Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
period, producing coarsely lava flows, such as plagioclase
Plagioclase
Plagioclase is an important series of tectosilicate minerals within the feldspar family. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a solid solution series, more properly known as the plagioclase feldspar series...
-hypersthene
Hypersthene
Hypersthene is a common rock-forming inosilicate mineral belonging to the group of orthorhombic pyroxenes. Many references have formally abandoned this term, preferring to categorise this mineral as enstatite or ferrosilite. It is found in igneous and some metamorphic rocks as well as in stony and...
-hornblende
Hornblende
Hornblende is a complex inosilicate series of minerals .It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole....
-phyric andesite
Andesite
Andesite is an extrusive igneous, volcanic rock, of intermediate composition, with aphanitic to porphyritic texture. In a general sense, it is the intermediate type between basalt and dacite. The mineral assemblage is typically dominated by plagioclase plus pyroxene and/or hornblende. Magnetite,...
. Proximal sections of lava flows contain vertical, well developed, large-diameter columnar joints, and lie beneath scoria
Scoria
Scoria is a volcanic rock containing many holes or vesicles. It is most generally dark in color , and basaltic or andesitic in composition. Scoria is relatively low in mass as a result of its numerous macroscopic ellipsoidal vesicles, but in contrast to pumice, all scoria has a specific gravity...
eous oxidized flow breccia, suggesting a possible subaerial origin. Distal sections of lava flows are glassy and contain minor diameter columnar joints with horizontal or nearby radiating orientations. Lava flow terminations appear as subvertical cliff
Cliff
In geography and geology, a cliff is a significant vertical, or near vertical, rock exposure. Cliffs are formed as erosion landforms due to the processes of erosion and weathering that produce them. Cliffs are common on coasts, in mountainous areas, escarpments and along rivers. Cliffs are usually...
s up to 200 metres (656.2 ft) in height, which are structures constant with eruptions against glacial ice.
Cauldron Dome
Cauldron Dome is a tuya in the Mount Cayley volcanic field, British Columbia, Canada. Cauldron Dome is made of coarsely plagioclase-orthophyroxene-phyric andesite lava flows and last erupted during the Holocene...
which also formed and last erupted during the Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
period. It consists of coarsely lava flows, such as plagioclase
Plagioclase
Plagioclase is an important series of tectosilicate minerals within the feldspar family. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a solid solution series, more properly known as the plagioclase feldspar series...
-orthophyroxene-phyric andesite
Andesite
Andesite is an extrusive igneous, volcanic rock, of intermediate composition, with aphanitic to porphyritic texture. In a general sense, it is the intermediate type between basalt and dacite. The mineral assemblage is typically dominated by plagioclase plus pyroxene and/or hornblende. Magnetite,...
. Its total geomorphology
Geomorphology
Geomorphology is the scientific study of landforms and the processes that shape them...
is comparable to that of a tuya
Tuya
A tuya is a type of distinctive, flat-topped, steep-sided volcano formed when lava erupts through a thick glacier or ice sheet. They are somewhat rare worldwide, being confined to regions which were covered by glaciers and also had active volcanism during the same time period.-Formation:Tuyas are...
. However, any precise record of volcanic glass
Volcanic glass
Volcanic glass is the amorphous product of rapidly cooling magma. Like all types of glass, it is a state of matter intermediate between the close-packed, highly ordered array of a crystal and the highly disordered array of gas...
or fine-scale jointing has probably been worn away by erosion. Two compositionally identical lava flows spread to the southwest from the base of the volcano. It is likely that Cauldron Dome was formed subglacially and the associated lava flows were erupted within a meltwater conduit.
Slag Hill
Slag Hill
Slag Hill is a subglacial volcano associated with the Mount Cayley volcanic field in British Columbia, Canada. It consists of glassy, augite-phyric basaltic andesite in steep-sided, glassy, finely jointed domes and one small, flat-topped bluff. The finely jointed domes are similar to those of Ember...
, another parasitic subglacial volcano located just north of Mount Cayley, was erupted during the Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
period, producing glassy lava flows, such as augite
Augite
Augite is a single chain inosilicate mineral, 2O6. The crystals are monoclinic and prismatic. Augite has two prominent cleavages, meeting at angles near 90 degrees.-Characteristics:Augite is a solid solution in the pyroxene group...
-phyric basaltic andesite
Basaltic andesite
Basaltic andesite is a black volcanic rock containing about 55% silica. Minerals in basaltic andesite include olivine, augite and plagioclase. Basaltic andesite can be found in volcanoes around the world, including in Central America and the Andes of South America. Basaltic andesite is common in...
. These lava flows were cooled to form steep-sided, glassy, finely jointed lava domes comparable to those found at Ember Ridge
Ember Ridge
Ember Ridge is a volcanic mountain ridge associated with the Mount Cayley volcanic field in British Columbia, Canada. Ember Ridge is made of a series of steep-sided domes of glassy, complexly jointed, hornblende-phyric basalt with the most recent eruptions during the Holocene...
, and one minor, flat-topped bluff
Cliff
In geography and geology, a cliff is a significant vertical, or near vertical, rock exposure. Cliffs are formed as erosion landforms due to the processes of erosion and weathering that produce them. Cliffs are common on coasts, in mountainous areas, escarpments and along rivers. Cliffs are usually...
.
Ring Mountain, just north of Slag Hill, is a parasitic tuya
Tuya
A tuya is a type of distinctive, flat-topped, steep-sided volcano formed when lava erupts through a thick glacier or ice sheet. They are somewhat rare worldwide, being confined to regions which were covered by glaciers and also had active volcanism during the same time period.-Formation:Tuyas are...
composed of plagioclase
Plagioclase
Plagioclase is an important series of tectosilicate minerals within the feldspar family. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a solid solution series, more properly known as the plagioclase feldspar series...
-hypersthene
Hypersthene
Hypersthene is a common rock-forming inosilicate mineral belonging to the group of orthorhombic pyroxenes. Many references have formally abandoned this term, preferring to categorise this mineral as enstatite or ferrosilite. It is found in igneous and some metamorphic rocks as well as in stony and...
-phyric andesite
Andesite
Andesite is an extrusive igneous, volcanic rock, of intermediate composition, with aphanitic to porphyritic texture. In a general sense, it is the intermediate type between basalt and dacite. The mineral assemblage is typically dominated by plagioclase plus pyroxene and/or hornblende. Magnetite,...
. The highest elevation of the volcano comprises bomb-like fragments of vesicular, oxidized lava, suggesting that the higher elevation lava flows were most likely subaerial. However, as is the case at volcanoes of comparable morphology elsewhere, lower elevations might have erupted subglacially.
Little Ring Mountain, also known as Little Ring Peak, is an almost circular, flat-topped, steep-sided volcanic feature about 270 metres (885.8 ft) in height and 120 metres (393.7 ft) wide on its top surface. It is known to be the northernmost parasitic cone and is similar in structure to a flat-topped, steep-sided tuya
Tuya
A tuya is a type of distinctive, flat-topped, steep-sided volcano formed when lava erupts through a thick glacier or ice sheet. They are somewhat rare worldwide, being confined to regions which were covered by glaciers and also had active volcanism during the same time period.-Formation:Tuyas are...
, although its inner stratigraphy
Stratigraphy
Stratigraphy, a branch of geology, studies rock layers and layering . It is primarily used in the study of sedimentary and layered volcanic rocks....
is not yet known because the area has not been studied in detail due to its remoteness.
Volcanic hazards
Tseax Cone
The Tseax Cone , also called the Tseax River Cone or alternately the Aiyansh Volcano, is a young cinder cone and adjacent lava flows associated with the Nass Ranges and the Northern Cordilleran Volcanic Province...
in 1775, when a 22.5 kilometres (14 mi) long basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
ic lava flow traveled down the Tseax
Tseax River
The Tseax River, also known as Ksi Sii Aks in the Nisga'a language, is a tributary of the Nass River in northwestern British Columbia, Canada. It is most notable as the namesake of Tseax Cone, a volcano within its basin that was responsible for an eruption that killed 2,000 Nisga'a people. Prior...
and Nass River
Nass River
The Nass River is a river in northern British Columbia, Canada. It flows from the Coast Mountains southwest to Nass Bay, a sidewater of Portland Inlet, which connects to the North Pacific Ocean via the Dixon Entrance...
s, destroying a Nisga'a
Nisga'a
The Nisga’a , often formerly spelled Nishga and spelled in the Nisga’a language as Nisga’a, are an Indigenous nation or First Nation in Canada. They live in the Nass River valley of northwestern British Columbia. Their name comes from a combination of two Nisga’a words: Nisk’-"top lip" and...
village and killing approximately 2,000 people by volcanic gas
Volcanic gas
|250px|thumb|right|Image of the [[rhyolitic]] [[lava dome]] of [[Chaitén Volcano]] during its 2008-2010 eruption.Volcanic gases include a variety of substances given off by active volcanoes...
es. Many towns and cities near Mount Cayley are home to well over half of British Columbia's human population, and there is a likelihood that future eruptions will cause damage to populated areas, making Mount Cayley and other Garibaldi belt volcanoes a major hazard. There are significant hazards from Canadian volcanoes that require hazard maps and emergency plains. Volcanoes which exhibit significant seismic activity, such as Mount Cayley, appear to be most likely to erupt. A significant eruption of the Garibaldi belt volcanoes would significantly impact Highway 99 and communities like Pemberton
Pemberton, British Columbia
Pemberton is a village north of Whistler in the Pemberton Valley of British Columbia in Canada, with a population of 2,192. Until the 1960s the village could be accessed only by train but that changed when Highway 99 was built through Whistler and Pemberton.-Climate:The climate of Pemberton is...
, Whistler
Whistler, British Columbia
Whistler is a Canadian resort town in the southern Pacific Ranges of the Coast Mountains in the province of British Columbia, Canada, approximately north of Vancouver...
and Squamish
Squamish, British Columbia
Squamish is a community and a district municipality in the Canadian province of British Columbia, located at the north end of Howe Sound on the Sea to Sky Highway...
, and possibly Vancouver
Vancouver
Vancouver is a coastal seaport city on the mainland of British Columbia, Canada. It is the hub of Greater Vancouver, which, with over 2.3 million residents, is the third most populous metropolitan area in the country,...
.
Eruption scenario
The western flank of the volcanic complex has been the site of several landslides. Several hot springHot spring
A hot spring is a spring that is produced by the emergence of geothermally heated groundwater from the Earth's crust. There are geothermal hot springs in many locations all over the crust of the earth.-Definitions:...
s exist high up on the western flank of the mountain. There have been shallow earthquakes close to Mount Cayley since 1985, and seismic studies by seismologists
Seismology
Seismology is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other planet-like bodies. The field also includes studies of earthquake effects, such as tsunamis as well as diverse seismic sources such as volcanic, tectonic, oceanic,...
and related geoscientist
Geoscientist
*For the Geological Society Magazine see Geoscientist *For Geoscientist see Earth science...
s have discovered a strong mid-crustal reflector below it consistent with an unusually large, solidified, mafic
Mafic
Mafic is an adjective describing a silicate mineral or rock that is rich in magnesium and iron; the term is a portmanteau of the words "magnesium" and "ferric". Most mafic minerals are dark in color and the relative density is greater than 3. Common rock-forming mafic minerals include olivine,...
, sill
Sill (geology)
In geology, a sill is a tabular sheet intrusion that has intruded between older layers of sedimentary rock, beds of volcanic lava or tuff, or even along the direction of foliation in metamorphic rock. The term sill is synonymous with concordant intrusive sheet...
-like intrusion
Intrusion
An intrusion is liquid rock that forms under Earth's surface. Magma from under the surface is slowly pushed up from deep within the earth into any cracks or spaces it can find, sometimes pushing existing country rock out of the way, a process that can take millions of years. As the rock slowly...
lying approximately 12.5 to 13 km (7.8 to 8.1 ) below the mountain. The eruptive scenario is based on past volcanic activity in the Garibaldi Volcanic Belt
Garibaldi Volcanic Belt
The Garibaldi Volcanic Belt, also called the Canadian Cascade Arc, is a northwest-southeast trending volcanic chain in the Pacific Ranges of the Coast Mountains that extends from Watts Point in the south to the Ha-Iltzuk Icefield in the north. This chain of volcanoes is located in southwestern...
, in terms of magnitude and sequence of events, to its neighbor Mount Meager
Mount Meager
Mount Meager, originally known as Meager Mountain, is a complex volcano in the Sea-to-Sky Corridor of southwestern British Columbia, Canada. It is located north of Vancouver at the northern end of the Pemberton Valley. Part of the Cascade Volcanic Arc of western North America, its summit is above...
about 2,350 years ago. This volcanic eruption was similar in size to the 1980 eruption of Mount St. Helens
1980 eruption of Mount St. Helens
The 1980 eruption of Mount St. Helens, a stratovolcano located in Washington state, in the United States, was a major volcanic eruption. The eruption was the only significant one to occur in the contiguous 48 U.S. states since the 1915 eruption of Lassen Peak in California...
and is Canada's most recent major eruption.
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
crust
Crust (geology)
In geology, the crust is the outermost solid shell of a rocky planet or natural satellite, which is chemically distinct from the underlying mantle...
. The large amount of seismicity and the sensitivity of the current seismograph
Seismometer
Seismometers are instruments that measure motions of the ground, including those of seismic waves generated by earthquakes, volcanic eruptions, and other seismic sources...
in this region would warn the Geological Survey of Canada and would most likely cause an expanded monitoring effort. As the magma rises to the surface, the mountain would probably swell and the surface would likely rupture, causing greatly increased vigour in the hot springs, and the formation of new hot springs or fumarole
Fumarole
A fumarole is an opening in a planet's crust, often in the neighborhood of volcanoes, which emits steam and gases such as carbon dioxide, sulfur dioxide, hydrochloric acid, and hydrogen sulfide. The steam is created when superheated water turns to steam as its pressure drops when it emerges from...
s on the mountainside. In other words, they would get hotter. Minor and possibly large landslides could occur and may perhaps temporarily dam the Squamish River
Squamish River
The Squamish River is a short but very large river in the Canadian province of British Columbia. Its drainage basin is in size. The total length of the Squamish River is approximately .-Course:...
, as happened in the past without earthquake shaking and intrusion
Intrusion
An intrusion is liquid rock that forms under Earth's surface. Magma from under the surface is slowly pushed up from deep within the earth into any cracks or spaces it can find, sometimes pushing existing country rock out of the way, a process that can take millions of years. As the rock slowly...
-related deformation. The continued presence of magma near the surface would eventually make contact with surface water, causing phreatic eruption
Phreatic eruption
A phreatic eruption, also called a phreatic explosion or ultravulcanian eruption, occurs when rising magma makes contact with ground or surface water. The extreme temperature of the magma causes near-instantaneous evaporation to steam, resulting in an explosion of steam, water, ash, rock, and...
s and debris flows, such as what occurred in the 1980 eruption of Mount St. Helens
1980 eruption of Mount St. Helens
The 1980 eruption of Mount St. Helens, a stratovolcano located in Washington state, in the United States, was a major volcanic eruption. The eruption was the only significant one to occur in the contiguous 48 U.S. states since the 1915 eruption of Lassen Peak in California...
. By this time Highway 99 would be closed and Squamish would be at least partially, and possibly entirely, abandoned.
Eruptive activity itself could continue for years, followed by years of decreasing secondary activity. Volcanic ash
Volcanic ash
Volcanic ash consists of small tephra, which are bits of pulverized rock and glass created by volcanic eruptions, less than in diameter. There are three mechanisms of volcanic ash formation: gas release under decompression causing magmatic eruptions; thermal contraction from chilling on contact...
would most likely spread throughout the Pacific Northwest
Pacific Northwest
The Pacific Northwest is a region in northwestern North America, bounded by the Pacific Ocean to the west and, loosely, by the Rocky Mountains on the east. Definitions of the region vary and there is no commonly agreed upon boundary, even among Pacific Northwesterners. A common concept of the...
, causing airports to be closed and relevant flights to be diverted or cancelled. The associated ash column
Eruption column
An eruption column consists of hot volcanic ash emitted during an explosive volcanic eruption. The ash forms a column rising many kilometres into the air above the peak of the volcano. In the most explosive eruptions, the eruption column may rise over 40 km, penetrating the stratosphere...
would then extend eastward by the prevailing winds and disrupt air traffic throughout Canada from Alberta
Alberta
Alberta is a province of Canada. It had an estimated population of 3.7 million in 2010 making it the most populous of Canada's three prairie provinces...
to Newfoundland and Labrador
Newfoundland and Labrador
Newfoundland and Labrador is the easternmost province of Canada. Situated in the country's Atlantic region, it incorporates the island of Newfoundland and mainland Labrador with a combined area of . As of April 2011, the province's estimated population is 508,400...
. The cooling lava would discontinuously spall units to create pyroclastic flow
Pyroclastic flow
A pyroclastic flow is a fast-moving current of superheated gas and rock , which reaches speeds moving away from a volcano of up to 700 km/h . The flows normally hug the ground and travel downhill, or spread laterally under gravity...
s (super-heated mix of gas
Gas
Gas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...
, ash, and pumice
Pumice
Pumice is a textural term for a volcanic rock that is a solidified frothy lava typically created when super-heated, highly pressurized rock is violently ejected from a volcano. It can be formed when lava and water are mixed. This unusual formation is due to the simultaneous actions of rapid...
). The loose volcanic rock and pyroclastic material on Cayley's flanks and in valleys would be periodically reactivated into debris flow
Debris flow
A debris flow is a fast moving, liquefied landslide of unconsolidated, saturated debris that looks like flowing concrete. It is differentiated from a mudflow in terms of the viscosity and textural properties of the flow. Flows can carry material ranging in size from clay to boulders, and may...
s. Considerable structural improvements would have to be made to reclaim use of Highway 99 and Squamish area.
Monitoring
Seismometer
Seismometers are instruments that measure motions of the ground, including those of seismic waves generated by earthquakes, volcanic eruptions, and other seismic sources...
has been established to monitor tectonic earthquakes and is too far away to provide a good indication of what is happening beneath the mountain. It may sense an increase in activity if the volcano becomes very restless, but this may only provide warning of a large eruption. It might detect activity only once the volcano has started erupting.
A possible way to detect an eruption is studying Cayley's geological history since every volcano has its own pattern of behavior, in terms of its eruption style, magnitude and frequency, so that its future eruption is expected to be similar to its previous eruptions.
While there is a likelihood of Canada being critically effected by local or close by volcanic eruptions argues that some kind of improvement program is required. Cost-benefit thoughts are critical to dealing with natural hazards. However, a cost-benefit examination needs correct data about the hazard types, magnitudes and occurrences. These do not exist for volcanoes in British Columbia or elsewhere in Canada in the detail required.
Other volcanic techniques, such as hazard mapping, displays a volcano's eruptive history in detail and speculates an understanding of the hazardous activity that could possibly be expected in the future. At present no hazard maps have been created for Mount Cayley because the level of knowledge is insufficient due to its remoteness. A large volcanic hazard program has never existed within the Geological Survey of Canada. The majority of information has been collected in a lengthy, separate way from the support of several employees, such as volcanologist
Volcanologist
A volcanologist is a person who studies the formation of volcanoes, and their current and historic eruptions. Volcanologists frequently visit volcanoes, especially active ones, to observe volcanic eruptions, collect eruptive products including tephra , rock and lava samples...
s and other geologic scientist
Scientist
A scientist in a broad sense is one engaging in a systematic activity to acquire knowledge. In a more restricted sense, a scientist is an individual who uses the scientific method. The person may be an expert in one or more areas of science. This article focuses on the more restricted use of the word...
s. Current knowledge is best established at Mount Meager
Mount Meager
Mount Meager, originally known as Meager Mountain, is a complex volcano in the Sea-to-Sky Corridor of southwestern British Columbia, Canada. It is located north of Vancouver at the northern end of the Pemberton Valley. Part of the Cascade Volcanic Arc of western North America, its summit is above...
just north of Mount Cayley and is likely to rise considerably with a temporary mapping and monitoring project. Knowledge at Mount Cayley and other volcanoes in the Garibaldi Volcanic Belt is not as established, but certain contributions are being done at least Mount Cayley. An intensive program classifying infrastructural exposure near young Canadian volcanoes and quick hazard assessment at each individual volcanic edifice associated with recent seismic activity would be in advance and would produce a quick and productive determination of priority areas for further efforts.
In countries like Canada it is possible that small precursor swarms might go undetected, particularly if no events were observed; more significant events in larger swarms would be detected but only a minor subdivision of the swarm events would be complex to clarify them with confidence as volcanic in nature, or even associate them with an individual volcanic edifice.
See also
- Cascade VolcanoesCascade VolcanoesThe Cascade Volcanoes are a number of volcanoes in a volcanic arc in western North America, extending from southwestern British Columbia through Washington and Oregon to Northern California, a distance of well over 700 mi ...
- Garibaldi Volcanic BeltGaribaldi Volcanic BeltThe Garibaldi Volcanic Belt, also called the Canadian Cascade Arc, is a northwest-southeast trending volcanic chain in the Pacific Ranges of the Coast Mountains that extends from Watts Point in the south to the Ha-Iltzuk Icefield in the north. This chain of volcanoes is located in southwestern...
- Cascade RangeCascade RangeThe Cascade Range is a major mountain range of western North America, extending from southern British Columbia through Washington and Oregon to Northern California. It includes both non-volcanic mountains, such as the North Cascades, and the notable volcanoes known as the High Cascades...
- Pacific RangesPacific RangesThe Pacific Ranges are the southernmost subdivision of the Coast Mountains portion of the Pacific Cordillera. Located entirely within British Columbia, Canada, they run northwest from the lower stretches of the Fraser River to Bella Coola, north of which are the Kitimat Ranges.The Pacific Ranges...
- Volcanism of Canada
- Volcanism of Western CanadaVolcanism of Western CanadaVolcanism of Western Canada produces lava flows, lava plateaus, lava domes, cinder cones, stratovolcanoes, shield volcanoes, submarine volcanoes, calderas, diatremes and maars, along with examples of more less common volcanic forms such as tuyas and subglacial mounds.-Volcanic belts:*Anahim...
- Geology of the Pacific NorthwestGeology of the Pacific NorthwestThe geology of the Pacific Northwest refers to the study of the composition , structure, physical properties and the processes that shape the Pacific Northwest region of the United States and Canada...
External links
- Volcanoes of Canada Garibaldi Volcanic Belt (Mount Cayley area)
- Catalogue of Canadian volcanoes - Mount Cayley