Mount Meager Massif
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The Mount Meager massif is a group of volcanic peaks in the of the
Coast Mountains The Coast Mountains (french: La chaîne Côtière) 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 ...
in southwestern
British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...
, Canada. Part of the
Cascade Volcanic Arc The Cascade Volcanoes (also known as the Cascade Volcanic Arc or the Cascade Arc) are a number of volcanoes in a volcanic arc in western North America, extending from southwestern British Columbia through Washington and Oregon to Northern Calif ...
of western North America, it is located north of
Vancouver Vancouver ( ) is a major city in western Canada, located in the Lower Mainland region of British Columbia. As the List of cities in British Columbia, most populous city in the province, the 2021 Canadian census recorded 662,248 people in the ...
at the northern end of the Pemberton Valley and reaches a maximum elevation of . The massif is capped by several eroded volcanic edifices, including ,
volcanic plug A volcanic plug, also called a volcanic neck or lava neck, is a volcanic object created when magma hardens within a vent on an active volcano. When present, a plug can cause an extreme build-up of high gas pressure if rising volatile-charged mag ...
s and overlapping piles of lava flows; these form at least six major summits including Mount Meager which is the second highest of the massif. The
Garibaldi Volcanic Belt The Garibaldi Volcanic Belt 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 ...
(GVB) has a long history of eruptions and poses a threat to the surrounding region. Any volcanic hazard ranging from
landslide Landslides, also known as landslips, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, deep-seated grade (slope), slope failures, mudflows, and debris flows. Landslides occur in a variety of ...
s to eruptions could pose a significant risk to humans and wildlife. Although the massif has not erupted for more than 2,000 years, it could produce a major eruption; if this were to happen, relief efforts would be quickly organized. Teams such as the
Interagency Volcanic Event Notification Plan The Interagency Volcanic Event Notification Plan (IVENP) is a program in Canada established to outline the notification procedure of some of the main agencies that would be involved in response to a volcanic eruption in Canada, an eruption close to ...
(IVENP) are prepared to notify people threatened by volcanic eruptions in Canada. The Mount Meager massif produced the largest volcanic eruption in Canada in the last 10,000 years. About 2,400 years ago, an explosive eruption formed a
volcanic crater A volcanic crater is an approximately circular depression in the ground caused by Volcano, volcanic activity. It is typically a bowl-shaped feature containing one or more vents. During Types of volcanic eruptions, volcanic eruptions, molten magm ...
on its northeastern flank and sent avalanches of hot ash, rock fragments and
volcanic gas Volcanic gases are gases given off by active (or, at times, by dormant) volcanoes. These include gases trapped in cavities (vesicles) in volcanic rocks, dissolved or dissociated gases in magma and lava, or gases emanating from lava, from volcanic ...
es down the northern flank of the volcano. Evidence for more recent volcanic activity has been documented at the volcano, such as
hot spring A hot spring, hydrothermal spring, or geothermal spring is a spring produced by the emergence of geothermally heated groundwater onto the surface of the Earth. The groundwater is heated either by shallow bodies of magma (molten rock) or by circ ...
s and
earthquake An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from ...
s. The Mount Meager massif has also been the source of several large landslides in the past, including a massive
debris flow Debris flows are geological phenomena in which water-laden masses of soil and fragmented rock rush down mountainsides, funnel into stream channels, entrain objects in their paths, and form thick, muddy deposits on valley floors. They generally ...
in 2010 that swept down
Meager Creek Meager Creek is a creek in the southern Pacific Ranges of the Coast Mountains in British Columbia, Canada. It flows northeast into the Lillooet River approximately northwest of the village of Pemberton and is adjacent to the Upper Lillooet P ...
and the Lillooet River.


Geography and geology


Regional geography

The Mount Meager massif lies in the
Coast Mountains The Coast Mountains (french: La chaîne Côtière) 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 ...
, which extend from
Vancouver Vancouver ( ) is a major city in western Canada, located in the Lower Mainland region of British Columbia. As the List of cities in British Columbia, most populous city in the province, the 2021 Canadian census recorded 662,248 people in the ...
to the
Alaskan Panhandle Southeast Alaska, colloquially referred to as the Alaska(n) Panhandle, is the southeastern portion of the U.S. state of Alaska, bordered to the east and north by the northern half of the Canadian province of British Columbia (and a small part ...
for . It is about wide, cut by
fjord In physical geography, a fjord or fiord () is a long, narrow inlet with steep sides or cliffs, created by a glacier. Fjords exist on the coasts of Alaska, Antarctica, British Columbia, Chile, Denmark, Germany, Greenland, the Faroe Islands, Ice ...
s, narrow inlets with steep cliffs created by glacial erosion. The Coast Mountains have a profound effect on British Columbia's climate. Lying just east of the Pacific Ocean, they shear off moisture-laden air coming off the ocean, causing heavy rainfall on their western slopes. This precipitation is among the most extreme in North America, feeding lush forests on the mountain range's western slopes. Valleys surrounding the massif contain old-growth forests. The area also features
wetland A wetland is a distinct ecosystem that is flooded or saturated by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free (anoxic) processes prevailing, especially in the soils. The ...
habitats, plants of the and glaucous willowherbs. Wildlife such as
wolves The wolf (''Canis lupus''; plural, : wolves), also known as the gray wolf or grey wolf, is a large Canis, canine native to Eurasia and North America. More than thirty subspecies of Canis lupus, subspecies of ''Canis lupus'' have been reco ...
,
wolverine The wolverine (), (''Gulo gulo''; ''Gulo'' is Latin for "gluttony, glutton"), also referred to as the glutton, carcajou, or quickhatch (from East Cree, ''kwiihkwahaacheew''), is the largest land-dwelling species of the family Mustelidae. It is ...
,
moose The moose (in North America) or elk (in Eurasia) (''Alces alces'') is a member of the New World deer subfamily and is the only species in the genus ''Alces''. It is the largest and heaviest extant species in the deer family. Most adult mal ...
, raptors,
black-tailed deer Two forms of black-tailed deer or blacktail deer that occupy coastal woodlands in the Pacific Northwest of North America are subspecies of the mule deer (''Odocoileus hemionus''). They have sometimes been treated as a species, but virtually all r ...
, and
waterfowl Anseriformes is an order of birds also known as waterfowl that comprises about 180 living species of birds in three families: Anhimidae (three species of screamers), Anseranatidae (the magpie goose), and Anatidae, the largest family, which in ...
inhabit the area as well as
grizzly The grizzly bear (''Ursus arctos horribilis''), also known as the North American brown bear or simply grizzly, is a population or subspecies of the brown bear inhabiting North America. In addition to the mainland grizzly (''Ursus arctos horri ...
and
black Black is a color which results from the absence or complete absorption of visible light. It is an achromatic color, without hue, like white and grey. It is often used symbolically or figuratively to represent darkness. Black and white have o ...
bear Bears are carnivoran mammals of the family Ursidae. They are classified as caniforms, or doglike carnivorans. Although only eight species of bears are extant, they are widespread, appearing in a wide variety of habitats throughout the Nor ...
s.


Regional geomorphology


Garibaldi Volcanic Belt

The Mount Meager massif is part of the
Garibaldi Volcanic Belt The Garibaldi Volcanic Belt 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 ...
(GVB), the northernmost segment of the . This
volcanic belt A volcanic belt is a large volcanically active region. Other terms are used for smaller areas of activity, such as volcanic fields. Volcanic belts are found above zones of unusually high temperature () where magma is created by partial melting ...
includes
cinder cone A cinder cone (or scoria cone) is a steep conical hill of loose pyroclastic fragments, such as volcanic clinkers, volcanic ash, or scoria that has been built around a volcanic vent. The pyroclastic fragments are formed by explosive eruptions o ...
s,
caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is ...
s,
stratovolcano A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and per ...
es and
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. Today they are most ...
es (volcanoes under glaciers or
ice sheet In glaciology, an ice sheet, also known as a continental glacier, is a mass of glacial ice that covers surrounding terrain and is greater than . The only current ice sheets are in Antarctica and Greenland; during the Last Glacial Period at Las ...
s) that have been active in the last 10,000 years. The latest explosive eruption in the Garibaldi Volcanic Belt occurred at a crater on the northeastern slope of the massif about 2,400 years ago, which forms a clearly defined depression. The GVB extends north from the Watts Point volcano to at least as far as the Meager massif. Because little is known about the volcanoes north of the massif, such as the Silverthrone and , experts disagree about their nature. Some scientists regard the Silverthrone Caldera as the northernmost volcano of the Garibaldi Volcanic Belt, while others contend that the geology of the massif more closely matches that of the GVB. It is also unclear whether the Milbanke Sound Cones are part of the Garibaldi Belt or formed by different tectonic processes. However, there is evidence the Silverthrone and complexes are related to activity at the
Cascadia subduction zone The Cascadia subduction zone is a convergent plate boundary that stretches from northern Vancouver Island in Canada to Northern California in the United States. It is a very long, sloping subduction zone where the Explorer, Juan de Fuca, and ...
. Geologically these two volcanoes contain the same rock types as those found elsewhere in the Cascade Arc, including
rhyolite Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained groundmass. The mineral ...
s,
dacite Dacite () is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyolite. ...
s,
andesite Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predomi ...
s and
basaltic andesite Basaltic andesite is a volcanic rock that is intermediate in composition between basalt and andesite. It is composed predominantly of augite and plagioclase. Basaltic andesite can be found in volcanoes around the world, including in Central Ameri ...
s. Such rock types are produced by subduction zone volcanism indicating volcanism at Silverthrone and is probably related to
subduction Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, the ...
. If these two volcanoes are true Cascade Arc volcanoes, the massif is not the northernmost volcano of the Garibaldi Belt or the Cascade Arc.


Cascade Volcanic Arc

Volcanism Volcanism, vulcanism or volcanicity is the phenomenon of eruption of molten rock (magma) onto the surface of the Earth or a solid-surface planet or moon, where lava, pyroclastics, and volcanic gases erupt through a break in the surface called ...
in the Cascade Volcanic Arc is caused by subduction of the Juan de Fuca Plate under the
North American Plate The North American Plate is a tectonic plate covering most of North America, Cuba, the Bahamas, extreme northeastern Asia, and parts of Iceland and the Azores. With an area of , it is the Earth's second largest tectonic plate, behind the Pacific ...
at the . This is a long
fault zone In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...
lying off the from
Northern California Northern California (colloquially known as NorCal) is a geographic and cultural region that generally comprises the northern portion of the U.S. state of California. Spanning the state's northernmost 48 counties, its main population centers incl ...
to southwestern British Columbia. The plates move at a relative rate of more than per year at an oblique angle to the subduction zone. Because of the huge fault area, the Cascadia subduction zone can produce large earthquakes of
magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...
7.0 or greater. The interface between the Juan de Fuca and North American plates remains locked for periods of roughly 500 years. During these periods,
stress Stress may refer to: Science and medicine * Stress (biology), an organism's response to a stressor such as an environmental condition * Stress (linguistics), relative emphasis or prominence given to a syllable in a word, or to a word in a phrase ...
builds up on the interface between the plates and causes
tectonic uplift Tectonic uplift is the geologic uplift of Earth's surface that is attributed to plate tectonics. While isostatic response is important, an increase in the mean elevation of a region can only occur in response to tectonic processes of crustal thick ...
of the North American margin. When the plate finally slips, it releases 500 years of stored energy in a massive earthquake. Unlike most subduction zones worldwide, there is no deep
oceanic trench Oceanic trenches are prominent long, narrow topographic depressions of the ocean floor. They are typically wide and below the level of the surrounding oceanic floor, but can be thousands of kilometers in length. There are about of oceanic tren ...
present along the
continental margin A continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters. It is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges. The continental margin ...
in Cascadia. The mouth of the
Columbia River The Columbia River (Upper Chinook: ' or '; Sahaptin: ''Nch’i-Wàna'' or ''Nchi wana''; Sinixt dialect'' '') is the largest river in the Pacific Northwest region of North America. The river rises in the Rocky Mountains of British Columbia, C ...
empties directly into the subduction zone and deposits
silt Silt is granular material of a size between sand and clay and composed mostly of broken grains of quartz. Silt may occur as a soil (often mixed with sand or clay) or as sediment mixed in suspension with water. Silt usually has a floury feel when ...
at the bottom of the
Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...
, burying this large depression, or area of sunken land. Massive floods from prehistoric
Glacial Lake Missoula Lake Missoula was a prehistoric proglacial lake in western Montana that existed periodically at the end of the last ice age between 15,000 and 13,000 years ago. The lake measured about and contained about of water, half the volume of Lake Mic ...
during the also deposited large amounts of
sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand an ...
into the trench. However, as with other subduction zones the outer margin is slowly being compressed like a giant spring. When the stored energy is suddenly released by slippage across the fault at irregular intervals, the Cascadia subduction zone can create enormous earthquakes such as the magnitude 9.0  Cascadia earthquake of January 26, 1700. However earthquakes along the Cascadia subduction zone are uncommon, and there is evidence of a decline in volcanic activity over the last few million years. The probable explanation lies in the rate of
convergence Convergence may refer to: Arts and media Literature *''Convergence'' (book series), edited by Ruth Nanda Anshen * "Convergence" (comics), two separate story lines published by DC Comics: **A four-part crossover storyline that united the four Wei ...
between the Juan de Fuca and North American plates, which converge at to per year, about half the rate of convergence from seven million years ago.


Local geography

Six main summits constitute the Mount Meager massif. The highest and northernmost summit is with an elevation of . Mount Meager itself is in elevation.
Capricorn Mountain Capricorn Mountain is one of the several volcanic peaks of the Mount Meager massif in southwestern British Columbia, Canada. The slopes of Capricorn Mountain appear to be more gentle than other volcanic peaks of the massif. The mountain consists o ...
west of Mount Meager rises with an elevation of . Just west of Capricorn Mountain lies
Mount Job Mount Job is one of six named volcanic peaks of the Mount Meager massif in British Columbia, Canada. It is a pile of rubble held together by volcanic ash and sand. The main summit of Mount Job is hard to climb because of difficult access and its ...
, in elevation. Pylon Peak with an elevation of is south of Capricorn Mountain and Mount Meager.
Devastator Peak Devastator Peak, also known as The Devastator, is the lowest and southernmost of the six subsidiary peaks that form the Mount Meager massif in southwestern British Columbia, Canada. It is located west of Bralorne. Geology Devastator Peak is a d ...
, also known as ''The Devastator'', has an elevation of and is the lowest and southernmost summit of the massif. Streams and glaciers have played a significant role in dissecting the massif, and its upper slopes are covered with snow and ice. Numerous feeder
dikes Dyke (UK) or dike (US) may refer to: General uses * Dyke (slang), a slang word meaning "lesbian" * Dike (geology), a subvertical sheet-like intrusion of magma or sediment * Dike (mythology), ''Dikē'', the Greek goddess of moral justice * Dikes ...
to older units, formed when magma intrudes into a crack then crystallizes as a
sheet intrusion A sheet intrusion, or tabular intrusion, is a planar sheet of roughly the same thickness, that forms inside a pre-existing rock.Essentials of Geology, 3rd Ed, Stephen Marshak When it cuts into another unlayered mass, or across layers, it is called ...
, are exposed by deep erosion. Perkin's Pillar, a vertical tower of
breccia Breccia () is a rock composed of large angular broken fragments of minerals or rocks cemented together by a fine-grained matrix. The word has its origins in the Italian language, in which it means "rubble". A breccia may have a variety of di ...
ted lava, represented an erosional remnant of the massif until its collapse in June 2005. More than 10 streams drain
meltwater Meltwater is water released by the melting of snow or ice, including glacial ice, tabular icebergs and ice shelves over oceans. Meltwater is often found in the ablation zone of glaciers, where the rate of snow cover is reducing. Meltwater can be ...
from the Mount Meager massif, including , Job Creek, No Good Creek, Angel Creek, Devastation Creek, Canyon Creek and . The massif is located within one of British Columbia's many territorial divisions known as the
Lillooet Land District The Lillooet Land District is one of the 59 cadastral subdivisions of British Columbia, which were created by the Lands Act of the Colony of British Columbia in 1859, defined as "a territorial division with legally defined boundaries for administra ...
.


Local geomorphology

The
geomorphology Geomorphology (from Ancient Greek: , ', "earth"; , ', "form"; and , ', "study") is the scientific study of the origin and evolution of topographic and bathymetric features created by physical, chemical or biological processes operating at or n ...
of the Mount Meager massif resembles that of
Glacier Peak Glacier Peak or Dakobed (known in the Sauk-Suiattle dialect of the Lushootseed language as "Tda-ko-buh-ba" or "Takobia") is the most isolated of the five major stratovolcanoes (composite volcanoes) of the Cascade Volcanic Arc in the U.S state of ...
, another Cascade Arc volcano in the
U.S. state In the United States, a state is a constituent political entity, of which there are 50. Bound together in a political union, each state holds governmental jurisdiction over a separate and defined geographic territory where it shares its sover ...
of
Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered o ...
. It consists of at least four overlapping stratovolcanoes that are younger from south to north. With a total volume of , the massif is older than most volcanoes in the Cascade Arc, tracing its history back to 2,200,000 years ago. In the
Cascade Range The Cascade Range or Cascades 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, ...
, the oldest volcanoes are generally no more than a million years old. This includes
Mount Rainier Mount Rainier (), indigenously known as Tahoma, Tacoma, Tacobet, or təqʷubəʔ, is a large active stratovolcano in the Cascade Range of the Pacific Northwest, located in Mount Rainier National Park about south-southeast of Seattle. With a s ...
(500,000 years old),
Lassen Peak Lassen Peak ( ), commonly referred to as Mount Lassen, is a lava dome volcano and the southernmost active volcano in the Cascade Range of the Western United States. Located in the Shasta Cascade region of Northern California, it is part of the ...
(25,000 years old), Mount Jefferson (290,000 years old) and
Mount St. Helens Mount St. Helens (known as Lawetlat'la to the indigenous Cowlitz people, and Loowit or Louwala-Clough to the Klickitat) is an active stratovolcano located in Skamania County, Washington, in the Pacific Northwest region of the United St ...
(50,000 years old). However, portions of the massif formed in the last million years. The volcano is made of
volcanic rock Volcanic rock (often shortened to volcanics in scientific contexts) is a rock formed from lava erupted from a volcano. In other words, it differs from other igneous rock by being of volcanic origin. Like all rock types, the concept of volcanic r ...
s ranging from
rhyodacite Rhyodacite is a volcanic rock intermediate in composition between dacite and rhyolite. It is the extrusive equivalent of those plutonic rocks that are intermediate in composition between monzogranite and granodiorite. Rhyodacites form from rapid ...
to
basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...
. Rhyodacite forms a series of eroded
volcanic plug A volcanic plug, also called a volcanic neck or lava neck, is a volcanic object created when magma hardens within a vent on an active volcano. When present, a plug can cause an extreme build-up of high gas pressure if rising volatile-charged mag ...
s which form the highest peaks. Their slopes are covered with their eruptive products and serve as the surface expressions of
intrusion In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and com ...
s. As a result, they provide a unique opportunity to study the relationships between
magma chamber A magma chamber is a large pool of liquid rock beneath the surface of the Earth. The molten rock, or magma, in such a chamber is less dense than the surrounding country rock, which produces buoyant forces on the magma that tend to drive it upw ...
s and their lavas. The
mafic A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks include ...
(rich in
magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...
and
iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...
), intermediate (between mafic and felsic) and
felsic In geology, felsic is a modifier describing igneous rocks that are relatively rich in elements that form feldspar and quartz.Marshak, Stephen, 2009, ''Essentials of Geology,'' W. W. Norton & Company, 3rd ed. It is contrasted with mafic rocks, whi ...
(rich in
feldspar Feldspars are a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagioclase'' (sodium-calcium) feldsp ...
and
quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical form ...
) volcanic rocks of the massif were erupted from at least eight volcanic vents.


Bridge River Vent

The Bridge River Vent is a relatively young volcanic crater that formed during an eruption about 2,400 years ago. This eruption ranged in character from explosive to effusive and involved
lava dome In volcanology, a lava dome is a circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruptions on ...
extrusion,
pyroclastic flow A pyroclastic flow (also known as a pyroclastic density current or a pyroclastic cloud) is a fast-moving current of hot gas and volcanic matter (collectively known as tephra) that flows along the ground away from a volcano at average speeds of bu ...
s,
lahar A lahar (, from jv, ꦮ꧀ꦭꦲꦂ) is a violent type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris and water. The material flows down from a volcano, typically along a river valley. Lahars are extreme ...
s and lava flows. Eastward migration of the spread material across
Western Canada Western Canada, also referred to as the Western provinces, Canadian West or the Western provinces of Canada, and commonly known within Canada as the West, is a Canadian region that includes the four western provinces just north of the Canada†...
to deposit the
Bridge River Ash The Bridge River Ash is a large geologically recent volcanic ash deposit that spans from southwestern British Columbia to central Alberta, Canada. The ash consists of dust-sized shards ellipsoidal fragments of pumice. It overlaps the Mount St. Hele ...
. In the and Lillooet River area the ash occurs as a coarse-textured deposit with blocks of
pumice Pumice (), called pumicite in its powdered or dust form, is a volcanic rock that consists of highly vesicular rough-textured volcanic glass, which may or may not contain crystals. It is typically light-colored. Scoria is another vesicular vol ...
up to in diameter. The texture rapidly becomes finer eastward from the Bridge River. At Big Bar on the
Fraser River The Fraser River is the longest river within British Columbia, Canada, rising at Fraser Pass near Blackrock Mountain in the Rocky Mountains and flowing for , into the Strait of Georgia just south of the City of Vancouver. The river's annual d ...
pellets are up to in diameter while pellets in the Messiter area have a maximum diameter of . Situated on the northeastern flank of Plinth Peak, the Bridge River Vent has an elevation of . It has oversteepened walls covered with ice and debris from volcanic activity and slope collapses. The crater is roughly bowl-shaped, although it is breached on the northern side. Because the Bridge River Vent is located on the northern slope of the Mount Meager massif, it represents a satellite vent. The eruption that formed the Bridge River Vent was probably fed through a conduit from the magma chamber below the massif. A
stress field A stress field is the distribution of internal forces in a body that balance a given set of external forces. Stress fields are widely used in fluid dynamics and materials science. Consider that one can picture the stress fields as the stress cre ...
controlled by regional
tectonics Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of mountain building, the growth and behavior of the strong, old cores of continents k ...
has been commonly invoked to explain the dynamics of lateral flow (flowing laterally rather than vertically toward the surface) of magma from a reservoir to produce such eruptions.


Human history


Naming

The name Meager Mountain was adopted on May 6, 1924, as labelled on a 1923 British Columbia map. In 1966 the volcano was renamed . According to a BC Geographical Names letter written in March 1983, "the local name, Cathedral, was duplicated elsewhere, so the mountain was renamed Meager after the creek of that name which lies to the south of it". Meager Creek is named after J. B. Meager who owned timber licences on the creek. Despite its official name, Mount Meager is sometimes mistakenly spelled ''Mount Meagre'' or . The massif's peak names were submitted by Canadian mountaineer Neal M. Carter, who was a member of the British Columbia Mountaineering Club. Devastator Peak was officially named on in association with Devastation Glacier. Plinth Peak was officially named on as identified in Carter's 1932 sketch map and article "Explorations in the Lillooet River Watershed". Mount Job and Pylon Peak were both officially named on January 17, 1957, from their labels on Carter's 1954 sketch map of the Lillooet River. Capricorn Mountain was originally identified as Mount Capricorn in the 1932
Canadian Alpine Journal The ''Canadian Alpine Journal'' is the yearly magazine of the Alpine Club of Canada. It serves as a worldwide journal of record for achievements in climbing, mountaineering, ski mountaineering, and exploration of mountains. The magazine is head ...
, Vol XXI. According to the journal, "the name chosen for the 8440-foot mountain was Mt. Capricorn, a variation of the all-too-common appellation "Goat Mountain", applied by Bert erkinsto the stream which drains the Capricorn glacier at its base". Subsequently, the peak was renamed to on June 22, 1967.


Mining and geothermal energy

A large pumice
outcrop An outcrop or rocky outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth. Features Outcrops do not cover the majority of the Earth's land surface because in most places the bedrock or superficial ...
more than long and wide has been the subject of
mining Mining is the extraction of valuable minerals or other geological materials from the Earth, usually from an ore body, lode, vein, seam, reef, or placer deposit. The exploitation of these deposits for raw material is based on the economic via ...
operations since at least the 1970s. The deposit was first held by J. MacIsaac. In the mid-1970s the second owner W. H. Willes investigated and mined the pumice. It was crushed, removed and stored close to the village of Pemberton. Later the bridge that was used to access the pumice deposit was washed out and mining operations were not renewed. Mining resumed in 1988 when the deposit was staked by L. B. Bustin. In 1990 the pumice outcrop was bought by D. R. Carefoot from the owners B. Chore and M. Beaupre. In a program from 1991 to 1992 workers evaluated the deposit for its properties as a construction material and as an absorber for oil and stonewash. About of pumice was mined in 1998 by the . The Mount Meager massif has been investigated as a potential
geothermal energy Geothermal energy is the thermal energy in the Earth's crust which originates from the formation of the planet and from radioactive decay of materials in currently uncertain but possibly roughly equal proportions. The high temperature and pres ...
resource. At least 16 geothermal sites have been identified in , the Mount Meager area being one of the five areas most capable of commercial development. At Meager Creek, there is potential for commercial development of a 100–200 
megawatt The watt (symbol: W) is the unit of Power (physics), power or radiant flux in the International System of Units, International System of Units (SI), equal to 1 joule per second or 1 kgâ‹…m2â‹…s−3. It is used to quantification (science), ...
power station A power station, also referred to as a power plant and sometimes generating station or generating plant, is an industrial facility for the generation of electric power. Power stations are generally connected to an electrical grid. Many p ...
. Nearby also has "very good" potential for a 200 megawatt plant. Because the two creeks offer the greatest potential for commercial development, the Mount Meager area is the most promising site for
geothermal power Geothermal power is electrical power generated from geothermal energy. Technologies in use include dry steam power stations, flash steam power stations and binary cycle power stations. Geothermal electricity generation is currently used in 2 ...
development in British Columbia.


Volcanic history

At least 54 eruptions have occurred at the massif in the last 2,600,000 years, ranging in character from effusive to explosive. Four primary eruptive periods have been identified, with individual eruptions separated by thousands of years. Large northwest–southeast trending structures paralleling
Harrison Lake Harrison Lake is the largest lake in the southern Coast Mountains of Canada, being about 250 square kilometres (95 mi²) in area. It is about 60 km (37 mi) in length and at its widest almost 9 km (5.6 mi) across. Its so ...
and the Pemberton Valley may control volcanic activity at the volcano or at least create zones of crustal weakness that are penetrated by rising magma batches.


First record of activity

During the first eruptive period between 2,200,000 and 1,900,000 years ago, eruption of intermediate to felsic pyroclastic rocks occurred at the southern end of the massif. Basal breccia, perhaps from an exhumed vent, underlies andesite and
tuff Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock cont ...
s, flows, lava domes and breccia of Devastator Peak. It has a maximum thickness of and overlies a high ridge of
bedrock In geology, bedrock is solid Rock (geology), rock that lies under loose material (regolith) within the crust (geology), crust of Earth or another terrestrial planet. Definition Bedrock is the solid rock that underlies looser surface mater ...
that formed between 251,000,000 and 65,500,000 years ago during the
Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceo ...
era. At the southwestern end of the massif, dacite with sparse
phenocryst 300px, feldspathic phenocrysts. This granite, from the Switzerland">Swiss side of the Mont Blanc massif, has large white plagioclase phenocrysts, triclinic minerals that give trapezoid shapes when cut through). 1 euro coins, 1 euro coin (diameter ...
s (large and conspicuous crystals) of
quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical form ...
,
plagioclase Plagioclase is a series of tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continuous solid solution series, more prope ...
and
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. Hornblende minerals are common in igneous and metamorphic rocks ...
represents a thick remnant of subhorizontal lava flows. Although the first eruptive period is generally estimated to have started about 2,200,000 years ago, two andesite eruptions may have occurred about 2,400,000 and 2,600,000 years ago. The first might have produced lava flows and breccia, whereas the latter may have erupted mainly breccia.


The Devastator and Pylon assemblage eruptive periods

The second eruptive period between 1,600,000 and 1,400,000 years ago produced rhyodacite tuff, breccia, lavas and domes of . This thick geological formation lies on the south and west flanks of Pylon Peak and Devastator Peak. Its western portion consists of roughly layered
tephra Tephra is fragmental material produced by a volcanic eruption regardless of composition, fragment size, or emplacement mechanism. Volcanologists also refer to airborne fragments as pyroclasts. Once clasts have fallen to the ground, they rem ...
while its eastern end represents the lava flows and
subvolcanic A subvolcanic rock, also known as a hypabyssal rock, is an intrusive igneous rock that is emplaced at depths less than within the crust, and has intermediate grain size and often porphyritic texture between that of volcanic rocks and plutonic r ...
intrusions of a partly preserved vent. Here, The Devastator Assemblage is massive and steeply truncates basal breccia from the first eruptive period. Volcanic activity of the third eruptive period occurred between 1,100,000 and 200,000 years ago. A thick sequence of andesite lava flows were erupted from the
volcanic plug A volcanic plug, also called a volcanic neck or lava neck, is a volcanic object created when magma hardens within a vent on an active volcano. When present, a plug can cause an extreme build-up of high gas pressure if rising volatile-charged mag ...
of Devastator Peak, creating the
Pylon Assemblage The Pylon Assemblage is an accreted terrane of igneous rocks in southwestern British Columbia, Canada, located about north of Vancouver. It is named after Pylon Peak, a summit of the Mount Meager massif. Two units make up the Pylon Assemblage, alt ...
. With a maximum thickness of more than , the Pylon Assemblage is the largest rock unit comprising the Mount Meager massif. The lava flows are layered, separated by a thin layer of
lapilli Lapilli is a size classification of tephra, which is material that falls out of the air during a volcanic eruption or during some meteorite impacts. ''Lapilli'' (singular: ''lapillus'') is Latin for "little stones". By definition lapilli range f ...
tuff and reddened breccia. A concentration of subvolcanic intrusions and coarse volcanic breccia clasts more than in length suggest that Devastator Peak is a major vent.


Formation of the Plinth, Job, Capricorn and Mosaic assemblages

The fourth and final eruptive period 150,000 to less than 3,000 years ago produced rhyodacite lava flows, domes, breccias and subvolcanic intrusions of the Plinth, Job and Capricorn assemblages. Around Mount Job,
porphyritic Porphyritic is an adjective used in geology to describe igneous rocks with a distinct difference in the size of mineral crystals, with the larger crystals known as phenocrysts. Both extrusive and intrusive rocks can be porphyritic, meaning all ...
hornblende,
biotite Biotite is a common group of phyllosilicate minerals within the mica group, with the approximate chemical formula . It is primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more alumino ...
and quartz rhyodacite lava flows of the
Job Assemblage The Job Assemblage is a geological formation comprising a portion of the Mount Meager massif in southwestern British Columbia, Canada. It is named after Mount Job, a subsidiary peak of Meager. The rock unit was formed during a period of rhyodacite v ...
were erupted. They are prominently layered and locally columnar jointed. On the east side of Affliction Glacier, they overlie porphyritic andesite lava flows of the Pylon Assemblage. Later, rhyodacite lava flows of the
Capricorn Assemblage The Capricorn Assemblage, also known as the Capricorn Formation, is a geological formation comprising the central portion of the Mount Meager massif in southwestern British Columbia, Canada. It is named after Capricorn Mountain, the third highest su ...
were erupted and flowed over biotite rhyodacite of the Job Assemblage. The upper of Capricorn Mountain and Mount Job are formed by these lava flows. Another sequence of rhyodacite lava flows were subsequently erupted and form the
Plinth Assemblage The Plinth Assemblage, also known as the Plinth Formation, is an accreted terrane of igneous rocks in southwestern British Columbia, Canada, located just north of the Lillooet River and on the northern flank of the Mount Meager massif. It is named ...
. Mount Meager, a massive lava dome or volcanic plug, consists of steeply inclined flow layering and was the southern source of Plinth Assemblage lava flows and breccias. Plinth Peak was also formed during the Plinth Assemblage eruptive stage and is mostly composed of prominent columnar or partly jointed lava flows. Its north ridge and flat-topped summit contain three areas of steep flow layering and subhorizontally-oriented columnar jointing. These areas are possibly the remains of volcanic plugs or lava domes that were the northern source of Plinth Assemblage lava flows. The
Mosaic Assemblage The Mosaic Assemblage is a rock unit of the Pacific Ranges of the Coast Mountains in southwestern British Columbia, Canada. It is the namesake of Mosaic Glacier, which is drained by Mosaic Creek. This geological formation formed 140,000 to les ...
, a sparsely porphyritic plagioclase-
augite Augite is a common rock-forming pyroxene mineral with formula . 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. ...
-
olivine The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers quickl ...
basalt and
trachybasalt Trachybasalt is a volcanic rock with a composition between trachyte and basalt. It resembles basalt but has a high content of alkali metal oxides. Minerals in trachybasalt include alkali feldspar, calcic plagioclase, olivine, clinopyroxene and li ...
formation, also formed during the fourth eruptive period. It is the remains of
scoria Scoria is a pyroclastic, highly vesicular, dark-colored volcanic rock that was ejected from a volcano as a molten blob and cooled in the air to form discrete grains or clasts.Neuendorf, K.K.E., J.P. Mehl, Jr., and J.A. Jackson, eds. (2005) ''G ...
ceous lava flows, breccias,
volcanic bomb A volcanic bomb or lava bomb is a mass of partially molten rock (tephra) larger than 64 mm (2.5 inches) in diameter, formed when a volcano ejects viscous fragments of lava during an eruption. Because volcanic bombs cool after they l ...
s and . The best known and most documented eruption of the Mount Meager massif is a large explosive eruption that occurred about 2,400 years ago. This eruption, which likely reached 5 on the , was similar to the 1980 eruption of Mount St. Helens. It sent a massive Plinian column at least high into the
atmosphere An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A s ...
. Prevailing westerly winds carried
volcanic ash Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, created during volcano, volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used t ...
from this explosion eastwards to as far as
Alberta Alberta ( ) is one of the thirteen provinces and territories of Canada. It is part of Western Canada and is one of the three prairie provinces. Alberta is bordered by British Columbia to the west, Saskatchewan to the east, the Northwest Ter ...
. Nearby areas were devastated by heavy
pyroclastic fall A pyroclastic fall is a uniform deposit of material which has been ejected from a volcanic eruption or plume such as an ash fall or tuff. Pyroclastic air fall deposits are a result of: # Ballistic transport of ejecta such as volcanic blocks, volca ...
when parts of the Plinian column collapsed. Later, a series of
pyroclastic flow A pyroclastic flow (also known as a pyroclastic density current or a pyroclastic cloud) is a fast-moving current of hot gas and volcanic matter (collectively known as tephra) that flows along the ground away from a volcano at average speeds of bu ...
s were erupted and travelled downstream. After this, a lava flow was erupted that repeatedly collapsed on the steep slopes of Plinth Peak, creating a thick, welded breccia deposit that blocked the Lillooet River. This created a lake just upstream which later collapsed to produce a massive . Large boulders were carried downstream for more than , but the destructive floodwaters continued further. Later, a small dacite lava flow was erupted, which cooled into well-preserved columnar joints. The entire eruption cycle originated from the Bridge River Vent on the northeastern flank of Plinth Peak. This is the latest known eruption of the Mount Meager massif, as well as the largest known Holocene explosive eruption in Canada. However, it is unknown when this eruption ended. In 1977, J. A. Westgate of the
University of Toronto The University of Toronto (UToronto or U of T) is a public research university in Toronto, Ontario, Canada, located on the grounds that surround Queen's Park. It was founded by royal charter in 1827 as King's College, the first institution ...
suggested that a smaller eruption may have occurred at the Bridge River Vent after the eruption 2,400 years ago, sending tephra southeast. A tephra deposit overlying the Bridge River Ash at Otter Creek shows strong genetic relationships with the Bridge River Ash, differing only by its absence of biotite. In earlier publications, this tephra is classified as part of the Bridge River Ash. However, it has been dated to be about 2,000 
radiocarbon year Radiocarbon dating measurements produce ages in "radiocarbon years", which must be converted to calendar ages by a process called calibration. Calibration is needed because the atmospheric / ratio, which is a key element in calculating radiocarbo ...
s old, indicating that this tephra is a few hundred years younger than the Bridge River Ash. Apparent absence of biotite and occurrence well south of the Bridge River Ash likewise favour a separate identity. Large-volume, fine-grained debris flows north of the volcano might have been caused by volcanic activity. If this is correct, the knowledge of eruptions at the Mount Meager massif in the last 10,000 years is insufficient.


Recent activity

Two small hot spring clusters are found at the Mount Meager massif, indicating magmatic heat is still present. These two clusters of hot springs, known as the Meager Creek Hot Springs and , are most likely related to recent volcanic activity at the massif. The , the largest in British Columbia, remain free of snow for most of the year. The springs at the Mount Meager massif might be evidence of a shallow magma chamber beneath the surface. Between 1970 and 2005 more than 20 small earthquakes were recorded at the volcano. The magnitudes of these events were generally no higher than 2.0 on the
Richter magnitude scale The Richter scale —also called the Richter magnitude scale, Richter's magnitude scale, and the Gutenberg–Richter scale—is a measure of the strength of earthquakes, developed by Charles Francis Richter and presented in his landmark 1935 ...
and they originated to less than below the surface. Other volcanoes in the with recorded
seismicity Seismicity is a measure encompassing earthquake occurrences, mechanisms, and magnitude at a given geographical location. As such, it summarizes a region's seismic activity. The term was coined by Beno Gutenberg and Charles Francis Richter in 19 ...
include
Mount Garibaldi Mount Garibaldi (known as Nch'kaý to the indigenous Squamish people) is a dormant stratovolcano in the Garibaldi Ranges of the Pacific Ranges in southwestern British Columbia, Canada. It has a maximum elevation of and rises above the surroundi ...
,
Mount Cayley Mount Cayley is an eroded but potentially active stratovolcano in the Pacific Ranges of southwestern British Columbia, Canada. Located north of Squamish and west of Whistler, the volcano resides on the edge of the Powder Mountain Icefield. ...
and . Seismic data suggest that these volcanoes still contain active magma chambers, indicating that some Garibaldi Belt volcanoes are probably active with significant potential hazards. The seismic activity corresponds with some of Canada's recently formed volcanoes and with persistent volcanoes that have had major explosive activity throughout their history such as Mount Garibaldi and the Mount Cayley and Mount Meager massifs.
Fumarolic A fumarole (or fumerole) is a vent in the surface of the Earth or other rocky planet from which hot volcanic gases and vapors are emitted, without any accompanying liquids or solids. Fumaroles are characteristic of the late stages of volcani ...
activity and
sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
smells were detected at the massif in 2016, with a fumarole field discovered on the Job Glacier. This was followed by
monitoring Monitoring may refer to: Science and technology Biology and healthcare * Monitoring (medicine), the observation of a disease, condition or one or several medical parameters over time * Baby monitoring * Biomonitoring, of toxic chemical compounds, ...
of the mountain by
Natural Resources Canada Natural Resources Canada (NRCan; french: Ressources naturelles Canada; french: RNCan, label=none)Natural Resources Canada is the applied title under the Federal Identity Program; the legal title is Department of Natural Resources (). is the depa ...
volcanologist A volcanologist, or volcano scientist, is a geologist who focuses on understanding the formation and eruptive activity of volcanoes. Volcanologists frequently visit volcanoes, sometimes active ones, to observe and monitor volcanic eruptions, col ...
s, the results of which did not detect much seismicity. The fumarole field was considered unsafe to approach or enter due to the presence of
hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The unde ...
and potentially unstable ice crevasses.


Threats and preparedness


Eruptions

The Mount Meager massif remains a major volcanic hazard, capable of producing highly explosive eruptions. A full-scale eruption would threaten many populated areas throughout southern British Columbia and Alberta. Pemberton, a community downstream from the massif, faces high risk. If the volcano were to erupt violently, it would disrupt the Lillooet River fishery as well as nearby
mining Mining is the extraction of valuable minerals or other geological materials from the Earth, usually from an ore body, lode, vein, seam, reef, or placer deposit. The exploitation of these deposits for raw material is based on the economic via ...
and
logging Logging is the process of cutting, processing, and moving trees to a location for transport. It may include skidding, on-site processing, and loading of trees or logs onto trucks or skeleton cars. Logging is the beginning of a supply chain ...
activity. In addition, the Mount Meager massif lies in the immediate proximity of a major air traffic route. Volcanic ash reduces visibility and can cause jet engine failure, as well as damage to flight control systems. Even a minor eruption from the volcano could cause massive devastation by rapidly melting glacial ice to produce large debris flows. An example of such an event is the 1985
Armero tragedy The Armero tragedy ( es, Tragedia de Armero, links=no ) occurred following the eruption of the Nevado del Ruiz stratovolcano in Tolima, Colombia, on November 13, 1985. The volcano's eruption after 69 years of dormancy caught nearby towns unawar ...
in
Colombia Colombia (, ; ), officially the Republic of Colombia, is a country in South America with insular regions in North America—near Nicaragua's Caribbean coast—as well as in the Pacific Ocean. The Colombian mainland is bordered by the Car ...
, which resulted from a small eruption under the summit ice cap of
Nevado del Ruiz The Nevado del Ruiz (), also known as La Mesa de Herveo ( en, Mesa of Herveo, the name of the nearby town) is a volcano on the border of the departments of Caldas and Tolima in Colombia, about west of the capital city Bogotá. It is a strat ...
.
Jack Souther Jack Gordon Souther (April 25, 1924 – June 1, 2014) was an American-born Canadian geologist, volcanologist, professor and engineer. He contributed significantly to the early understanding of recent volcanic activity in the Canadian Cordillera. ...
, a leading authority on geothermal resources and volcanism in the Canadian Cordillera, expressed concern about the potential for another eruption:
At present the volcanoes of the Garibaldi Belt are quiet, presumed dead but still not completely cold. But the flare-up of Meager Mountain 2,500 years ago raises the question, "Could it happen again?" Was the explosive eruption of Meager Mountain the last gasp of the Garibaldi Volcanic Belt or only the most recent event in its on-going life? The short answer is nobody really knows for sure. So just in case I sometimes do a quick check of the old hot-spots when I get off the Peak Chair.
Because of concerns about potential eruptions and danger to communities in the area, the plans to create hazard maps and emergency plans for the Mount Meager massif as well as Mount Cayley to the south. Although very few eruptions in Canada have been witnessed by people, it remains nonetheless an area of intense volcanic activity. According to the Geologic Hazards '91 Workshop, "priority should be given to eruption impact studies of the two recently active volcanic centres closest to urban areas, Mount Baker and Mount Meager. The former case will require a combined US-Canada-Washington State-B.C. effort". The Mount Meager massif is not monitored closely enough by the to ascertain how active its magma system is. The
Canadian National Seismograph Network The Canadian National Seismograph Network is a network of seismographs to detect earthquakes across Canada. It is operated by the Geological Survey of Canada The Geological Survey of Canada (GSC; french: Commission géologique du Canada (CGC)) is ...
has been established to monitor earthquakes throughout Canada, but it is too far away to provide an accurate indication of activity under the mountain. It may sense an increase in seismic activity if the massif becomes highly restless, but this may only provide a warning for a large eruption; the system might detect activity only once the volcano has started erupting. If the Mount Meager massif were to erupt, mechanisms exist to orchestrate relief efforts. The Interagency Volcanic Event Notification Plan (IVENP) was created to outline the notification procedure of some of the main agencies that would respond to an erupting volcano in Canada, an eruption close to the
Canada–United States border The border between Canada and the United States is the longest international border in the world. The terrestrial boundary (including boundaries in the Great Lakes, Atlantic, and Pacific coasts) is long. The land border has two sections: Can ...
or any eruption that would affect Canada. Although the Mount Meager massif is a potentially active volcano, as of 2016 there was no evidence of an imminent eruption. Many shallow earthquakes normally occur before a volcano erupts. As magma rises to the surface over time, it will probably create much more vigour and heat at the regional hot springs, as well as the formation of new springs or
fumarole A fumarole (or fumerole) is a vent in the surface of the Earth or other rocky planet from which hot volcanic gases and vapors are emitted, without any accompanying liquids or solids. Fumaroles are characteristic of the late stages of volcani ...
s. These signs generally occur for weeks, months or years before a potential eruption, although the possibility of an eruption occurring in the near future remains low. A significant structural collapse associated with loss of glacial buttressing might affect the magma plumbing system and lead to an eruption.


Landslides

Scientists have argued that the Mount Meager massif, made of altered volcanic rock which breaks apart easily, is the most unstable mountain massif in Canada and may also be its most active landslide area. More than 25 landslides have occurred there in the last 8,000 years, and debris flows, mainly from the massif, have also filled Meager Creek valley to a depth of . Large volcano-associated debris flows known as lahars pose a threat to populated areas downstream from glaciated volcanoes. Although lahars are typically associated with the effects of volcanic eruptions, they can occur whenever conditions allow collapse and movement of mud originating from existing
volcanic ash Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, created during volcano, volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used t ...
deposits. Melting snow and ice, intense rainfall or the breakout of a summit
crater lake Crater Lake (Klamath language, Klamath: ''Giiwas'') is a volcanic crater lake in south-central Oregon in the western United States. It is the main feature of Crater Lake National Park and is famous for its deep blue color and water clarity. The ...
can all generate lahars. Landslides at the Mount Meager massif may also be indirectly related to
climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
. Several tension cracks extend up to the summit, and as
global warming In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
causes glaciers to melt, the meltwater reaches deep into the massif. It then flows along the ruptured surfaces creating landslide zones. Because the Mount Meager massif is capable of producing large landslides, Meager Creek valley is probably the most dangerous valley in the . Rapidly growing communities down the Lillooet River valley, such as Pemberton, are vulnerable despite their distance from the massif. As Pemberton continues to grow it will eventually extend into the surrounding mountains, creating a major hazard for people living there. The landslide risk is somewhat mitigated by the Lillooet River Early Warning System which was established in 2014 to alert the Pemberton Valley of landslides. Monitoring is done by measuring the Lillooet River water level using two sensors: one on the Hurley River Forestry Bridge and the other in the river. Damming of the Lillooet River by a landslide would be indicated by the lowering of the water level while the release of a
landslide dam A landslide dam or barrier lake is the natural damming of a river by some kind of landslide, such as a debris flow, rock avalanche or volcanic eruption. If the damming landslide is caused by an earthquake, it may also be called a quake lake. Some ...
would be followed by water level rise.


Prehistoric


Historic


=1975 landslide

= A massive rock avalanche occurred at the massif on July 22, 1975. With a volume of , it buried and killed a group of four geologists at the confluence of Devastation Creek and Meager Creek. The landslide originated on the western flank of Pylon Peak and flowed down Devastation Creek for . Geologic studies have shown that the landslide was the result of a complex history of glacial erosion, loading and unloading of the toe (a protrusion at the front of the slide mass) caused by the
Little Ice Age The Little Ice Age (LIA) was a period of regional cooling, particularly pronounced in the North Atlantic region. It was not a true ice age of global extent. The term was introduced into scientific literature by François E. Matthes in 1939. Ma ...
advance and subsequent retreat of Devastation Glacier due to global warming.


=2010 landslide

= On August 6, 2010, a massive debris flow cascaded down from Capricorn Glacier at a speed of per second. Experts initially estimated that the volume of debris totaled , which would make it the second largest landslide on record in Canadian history, behind the that removed of rock from Johnson Peak, a mountain in the Nicolum Valley near Hope, British Columbia. However, the landslide was later estimated to be more than , which would make it the largest of all time in Canada. The 2010 landslide was wide and long, creating a dam across Meager Creek and the Lillooet River. This created a lake just upstream. Early concerns that the dam might collapse and flood the Lillooet River valley ended a day later, when part of the dam ruptured and slowly released the accumulated water. An evacuation alert was rescinded, and nearly 1,500 residents were allowed to return to their homes on the weekend after the landslide occurred. No injuries were reported.


See also

*
List of Cascade volcanoes This is a list of Cascade volcanoes, i.e. volcanoes formed as a result of subduction along the Cascadia subduction zone in the Pacific Northwest of North America. The volcanoes are listed from north to south, by province or state: British Columbi ...
*
List of volcanoes in Canada List of volcanoes in Canada is an incomplete list of volcanoes found in Mainland Canada, in the Canadian islands and in Canadian waters. All but one province, Prince Edward Island, have at least one volcano. Alberta British Columbia Ne ...
* Salal Glacier volcanic complex * Sham Hill * Tuber Hill *
Volcanology of Western Canada Volcanism of Western Canada has produced lava flows, lava plateaus Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be eru ...


References


External links

* * * * * * * * * * * * * {{DEFAULTSORT:Meager, Mount Volcanic plugs of British Columbia Stratovolcanoes of Canada Active volcanoes VEI-5 volcanoes Subduction volcanoes Pleistocene lava domes Complex volcanoes Natural disasters in British Columbia Hot springs of British Columbia Pacific Ranges Pleistocene stratovolcanoes Polygenetic volcanoes Landslides in Canada Two-thousanders of British Columbia