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Image by Enrique from Pixabay
GeoNotes Volcanoes in Canada
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Canadian volcanoes are part of the Pacific Ring of Fire. Source: worldmapblank.com
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Volcanism occurs along continental plate boundaries. Source: worldmapblank.com
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Location of Major and Minor Canadian Volcanoes. Canadian vents (greytriangles), lumped volcanoes (redtriangles), and volcanic belts/provinces. Garibaldi volcanic belt (GVB); Chilcotin basalts (CB); Anahim volcanic belt (AVB); Clearwater–Quesnel volcanic province (CQVP); Northern Cordilleran volcanic province (NCVP). Source: Kelman, Melanie C.; Wilson, Alexander M.; Canadian Journal of Earth Sciences; Vol. 61; No. 3; March 2024; Pgs. 408-430
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Source: Kelman, Melanie C.; Wilson, Alexander M.; Canadian Journal of Earth Sciences; Vol. 61; No. 3; March 2024; Pgs. 408-430
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‘Ka’ is thousands of years, and ‘belt’ is the mountain belt where the volcano is situated, see previous map. Source: Kelman, Melanie C.; Wilson, Alexander M.; Canadian Journal of Earth Sciences; Vol. 61; No. 3; March 2024; Pgs. 408-430
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Source: Kelman, Melanie C.; Wilson, Alexander M.; Canadian Journal of Earth Sciences; Vol. 61; No. 3; March 2024; Pgs. 408-430
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Source: Daily Mail, US Edition, October 25, 2023 |
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Wikipedia: Cascade Volcanoes |
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Structure of the Earth Source: age-of-the-sage.org |
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Source: age-of-the-sage.org Earth’s fragmented crust moves due to currents in the mantle and asthenosphere. The hotter material rises, displacing the cooler material, creating the currents. |
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The dynamics of two converging plates. The active continental magmatic arc is equivalent to the Cascade and Aleutian volcanic arcs of the western North American Cordilleran mountain range. Not to be confused with island arcs, which are the same process except that volcanoes rise out of the ocean. Source: Pinterest
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The Earth’s major continental plates. Red arrows indicate the direction of movement. Source: age-of-the-sage.org |
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Source: age-of-the-sage.org |
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Process of creating an earthquake. Source: Ocean Data Labs, Rutgers University |
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The tectonic plates and volcanic dynamics. (CVA) Cascade and (AVA) Aleutian volcanic arcs, (QCF) Queen Charlotte Fault, (DF) Denali Fault, (TF-RMT) Tintina-Rocky Mountain Trench Fault, (JdF) Juan de Fuca. Source: Russell, James Kelly; et al; Canadian Journal of Earth Sciences; Vol. 60; No. 10; October 2023; Pgs. 1443-1466. |
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Complex plate movements. Source: Wikipedia: Cascade Volcanoes |
The Main Types of Volcanoes:
Cinder Cones (Scoria Cones)
the simplest and most common type of volcanoes
the initial eruption is a gas-rich magma that rises through a vent, fragmenting as it escapes, creating ash and cinders
a cone structure is built by the accumulation of pyroclastic material around the vent
continuing explosive events create a crater at the summit
lava may flow out of the cone and into the surrounding area
sometimes the cones form in isolation (example, Paricutin in Mexico), but commonly form in connection with other volcanoes
cinder cones do not trigger larger volcanic eruptions and are not connected to larger magma chambers
common on the flanks of shield volcanoes (Hawaii) and stratovolcanoes can have cinder cones on their slopes that have formed from minor eruptions away from the main summit vent
smallest volcano type built from a single eruption expelling volcanic debris, ash, cinders (solidified lava fragments), lapilli (small stones), and volcanic bombs (rock)
a prominent crater formed from the explosive ejection of material often sits at the summit
cone symmetrical unless the ejected material has been wind redistributed
cone is the main body of the volcano and consists of alternating layers of volcanic ash, cinders, and occasional lava flows
usually less than 400 m (1312.34 feet) tall, slopes often steep 30-40 degrees
magma composition basaltic to andesitic
magma erupts through a vent, an opening at the ground surface; some cinder cones have additional vents
may erupt only once (monogenetic volcanoes), often lasting from several days to a few years
cinder cones occur in the western US and Canada, and throughout the world
they also erupt beneath the ocean
generally less hazardous compared to the larger volcanoes; however, lava flows, ash fall, and explosive eruptions can pose a risk to populations, property, aviation, and air quality
Composite Volcanoes (Stratovolcanoes)
classic volcano shape, tall, symmetrical cones, erupt violently, and are formed by multiple layers of accumulation of hardened lava, tephra, pumice, volcanic ash, and rock
they dominate the landscape, and the structure derives its name from alternating layers of viscous lava and tephra (fragmented volcanic material)
they form when the oceanic plate subducts beneath the continental plate, which produces friction, creating maga which rises to the surface, creating a volcano.
have a reservoir containing molten rock beneath the surface (magma chamber), a passage through which magma travels (conduit) to the surface, and an opening at the surface through which volcanic material is expelled (vent)
the location of the main vent can change over time
parasitic vents and cones can form
surrounding the vent is a bowl-shaped depression (crater), sometimes containing fumaroles (gas vents), lakes or ice.
streams of molten rock (lava flows), solidifying as it cools, fast-moving currents of hot gases and volcanic material (pyroclastic flows), and volcanic mud flows or debris flows (lahars) with composition either thick and slow-moving or liquid and fast-moving
steep profile with conical slopes
explosive eruptions due to high viscosity and gas content of the magma
remain dormant for centuries between eruptions (polygenetic volcanoes), during which erosion takes place
renewed activity and warning signs that the volcano is becoming active are seismic activity (earthquakes), ground deformation, either bulging or uplifting of the volcano’s surface, changes in gas emissions (increased sulphur dioxide), and the formation of new volcanic gas vents (fumaroles)
a renewed eruption adds layers to the volcano’s surface
when the magma supply dwindles, the volcano becomes extinct
up to 2400 m (8000 feet) in elevation, towering over the surrounding landscape
lava composition andesitic to rhyolitic
examples are the tall volcanoes of the western North American Cordilleran Mountains, and throughout the world
they are extremely dangerous and usually make breaking news with the larger volcanoes, temporarily disrupting the climate by releasing ash and gases into the atmosphere
the also form at subduction zones beneath the ocean and eventually can emerge as island arcs
monitored using seismographs, gas sensors, satellite imagery, and ground-based observations
Shield Volcano
broad-based, shield-like profile with gentle slopes formed by the flow of low viscosity basaltic (low silica) lava travelling long distances before cooling and solidifying
form at hot spots (Hawaii) and divergent plate boundaries (Mid-Atlantic Ridge)
lava originates from the mantle, rises through the crust at hot spots or divergent plate boundaries, magma chamber fills, increasing pressure, which creates fissures in the crust, allowing magma to escape as lava
magma can erupt as fountains from the fissures, creating splatter cones
magma can escape through fissures and vents
as the surface lava cools and solidifies, the molten lava beneath continues to flow, creating lava tubes
the eruption sequence begins with vigorous lava fountaining and the formation of lava flows, followed by a steady flow of lava creating extensive lava fields, and in the decline phase, reduced lava flow and cooling of the lava
as magma chamber expands surface bulges and tilts, creating seismic activity, higher gas emissions such as sulphur dioxide, and thermal anomalies
eruptions are non-explosive, frequently producing extensive lava flows rather than violent pyroclastic activity
low-angled slopes, typically between 2-10 degrees
characteristic features: summit caldera is a basin-like depression at the summit formed when magma chamber has emptied and the ground above collapsed, vents through which magma erupts can occur at the summit or on the flanks of the volcano, molten lava lakes sometimes form in the summit caldera, rift or fissure zones are crustal cracks allowing magma to erupt from elongated fissures, lava flows stream down the slopes of the volcano, lava tubes are conduits formed by flowing lava beneath the hardened surface, vog is volcanic smog consisting of sulfure dioxide and other gases, and laze plumes are steam plumes formed when lava enters the ocean creating hydrochloric acid and volcanic glass particles
hazards: lava flows are slow moving giving warning but do destroy property and infrastucture, vog can cause respiratory issues and other health problems, laze plumes hazardous to breathe and cause skin and eye irritation, earthquakes cause land slides and can cause structural damage, gas emissions of sulfur dioxide and carbon dioxide can be harmful to humans and animals causing suffocation as the oxygen is displaced
less dangerous than stratovolcanoes
example: Mauna Kea, Hawaii, is the tallest mountain on earth, 9330 m (30,610 ft)
Supervolcano
form when magma rises into the crust but is unable to break through, creating pressure buildup in a large and growing magma pool until the crust is unable to contain the pressure and ruptures, creating a massive blowout
can occur at hotspots (Yellowstone Caldera) or subduction zones (Lake Toba, Indonesia)
massive volcano that can eject more than 1000 cubic km of tephra (mix of volcanic ash, rock fragments, and gases)
not defined by towering cone shape structure, but rather massive depressions (calderas) formed after the magma chamber beneath the volcano emptied, causing the land above to collapse.
calderas can be tens of miles across
Volcanic Explosivity Index (VEI) of a supervolcano is 8, as compared to Mount St. Helens, 5
considered to be 1000 times more powerful than regular volcanoes
colossal eruptions that produce thick ash, which can have global consequences on climate and ecosystems which can last for several years
the process begins with magma built up over time during a long dormancy; the massive magma chamber exerts pressure on the Earth’s crust, causing it to weaken, resulting in a catastrophic supereruption; the magma chamber empties, and the ground collapses, creating a caldera
lie dormant for centuries before erupting
predicting their eruptions is difficult; eruption patterns can vary greatly; however, at Yellowstone, the three recent major eruptions occurred roughly every 600,00-800,00 years with the last eruption about 70,000 years ago
early signs of detection are seismic activity to detect movement of magma beneath the surface, and deformation monitoring of the ground above the magma chamber using GPS and satellite imaging technology, monitoring gas emission, particularly sulphur dioxide
Pyroclasts and Pyroclastic Rocks
The following definitions of pyroclasts and pyroclastic rocks are copied from the US National Park Service.
Collectively, the fragments ejected during explosive eruptions are termed pyroclasts, meaning “fire-broken” from the ancient Greek. Pyroclasts may be ejected while still molten or partially molten, or may consist of solidified magma or of other rock fragments.
Pyroclasts may also include individual crystals, crystal fragments, and fragments of volcanic glass. Cinders, ash, and volcanic bombs are all pyroclasts. Pyroclasts are derived from either the magma itself or are plucked as solid pieces from the walls of the conduit, usually near the surface.
Pyroclasts
Pyroclasts are classified by size and shape as follows:
Ash: A pyroclast grain with a diameter less than 2 mm (0.08 inches).
Lapilli: A pyroclast with a mean diameter between 2 and 64 mm ( 0.08 and 2.5 inches).
Block: A pyroclast with a diameter greater than 64 mm (2.5 inches) and that has an angular shape. Blocks are solid during eruption and transport.
Bomb: A pyroclast with a diameter greater than 64 mm (2.5 inches) and that has a rounded or ellipsoidal shape that indicates that it was wholly or partially molten during eruption and flight.
Types of Volcanic Bombs
Most volcanic bombs solidify during flight, although some are still partially plastic when they land. The shapes of bombs are determined largely by the viscosity of the magma/lava, the length and velocity of flight, how rapidly they cooled, the expansion of vesicles (gas bubbles) within them, and any deformation upon impact. Most volcanic bombs are made of basaltic or intermediate lavas because these lava types have relatively low viscosity.
Spindle bombs: Almond-shaped bombs that result from the tearing apart of ribbons of lava either during flight or upon impact with the ground.
Ribbon bombs: Elongated ropy-shaped bombs.
Cowdung bombs: Very fluid bombs which flatten or splash upon landing.
Breadcrust bombs: Bombs with a fractured surface from a quickly quenched crust that was fractured by continued expansion of vesicles within a molten core. Most breadcrusting forms after landing. Breadcrust bombs are usually andesitic in composition.
Cored bombs: Bombs that have a nucleus of solid material. The solid core may be fragments of previously solidified magma from the volcano, or a xenolith (foreign rock fragment from either the crust or the mantle).
Spindle, ribbon, and cowdung bombs are commonly produced during Strombolian or other low intensity eruptions that form cinder cones.
Pele’s Tears and Hair
Pele’s Tears and Pele’s Hair are delicate pyroclasts produced in Hawaiian style eruptions such as at Kilauea, a shield volcano in Hawaii Volcanoes National Park. Both are named after Pele, the Hawaiian volcanic deity.
Pele’s Tears: Small droplets of volcanic glass shaped like glass beads. They are frequently attached to filaments of Pele’s Hair.
Pele’s Hair: Thin threads of volcanic glass that are produced during eruptions of gas-rich fluid lavas. These filaments form as lava droplets are drawn into threads.
Pumice, Scoria, and Cinders
Pumice, scoria, and cinders are specific types of highly vesicular pyroclastic rocks, although the distinction between them is somewhat arbitrary. Vesicles are small cavities in volcanic rocks that formed as bubbles that grew because of the exsolution of gases escaping from the magma upon eruption. Vesicles may be spherical, lens-shaped, tubular, or highly irregular.
Pumice: A light-colored, highly vesicular rock in which small, closely-spaced vesicles are separated by very thin walls of glass. It is usually formed in highly explosive pyroclastic eruptions. Pumice is typically rhyolitic in composition, but dacite or rhyodacite pumice may also form. Pumice typically has such a high concentration of vesicles that it is buoyant and can float on water.
Scoria: A dark-colored highly vesicular rock in which the vesicles are so numerous that they constitute the majority of the volume of the rock. Scoriaceous structure occurs in lapilli and bombs thrown out in explosive eruptions of mafic to intermediate compositions. It also can form in the rapidly cooled upper and lower surfaces of mafic lava flows.
Cinder - A colloquial term for a small nut-size to fist-size, or larger, piece of red or black highly vesicular lava that cooled in air during flight after eruption from a vent. It is roughly synonymous with scoria.
Pyroclastic Deposits
Pyroclastic
deposits may consist of both unconsolidated accumulations of
pyroclasts, and rocks made up of pyroclasts.
Pyroclastic rocks
have characteristics of both igneous or sedimentary rocks. They are
composed exclusively of volcanic materials, yet are made up of
fragments and grains like sedimentary rocks, and may be reworked by
wind and flowing water. Welding is the process by which hot plastic
pyroclasts are lithified into rock as a result of heat and the weight
of overlying material.
Tephra - The collective term for unconsolidated pyroclastic deposits.
Tuff - A consolidated pyroclastic rock made primarily of ash.
lgnimbrite - An ash-flow tuff is deposited by a pyroclastic flow (a “volcanic hurricane”) which forms from either the collapse of a large eruption column or a dome, or from “boiling over” in an explosive eruption (no large eruption column produced).
Spatter - An accumulation of highly molten bombs that land while still molten and weld together to form solid rock, spatter cones, or sometimes feed lava flows. Spatter is formed from fire fountains and spatter deposits are only formed near a vent.
Another source: SaskOER, downloadable physical geology textbook: DownloadPDF Files – Physical Geology, First University of SaskatchewanEdition.
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A generalized geologic time scale. ‘Ma’ is an abbreviation for millions of years. The asterisks indicate major extinction events, and the question mark asterisk is a possible major extinction event currently underway. Image modified after USGS.
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Created on: 2025
Updated: 12-24-2025
