The Cascadia subduction zone is a convergent plate boundary that stretches from northern Vancouver Island in

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...

to Northern California in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

. It is a very long, sloping subduction zone where the

Explorer Exploration refers to the historical practice of discovering remote lands. It is studied by geographers and historians. Two major eras of exploration occurred in human history: one of convergence, and one of divergence. The first, covering most ...

Juan de Fuca Juan de Fuca (10 June 1536, Cefalonia 23 July 1602, Cefalonia)Greek Consulate of Vancouver,Greek Pioneers: Juan de Fuca. was a Greek pilot who served PhilipII of Spain. He is best known for his claim to have explored the Strait of Aniánnow k ...

, and Gorda plates move to the east and slide below the much larger mostly continental North American Plate. The zone varies in width and lies offshore beginning near

Cape Mendocino Cape Mendocino (Spanish: ''Cabo Mendocino'', meaning "Cape of Mendoza"), which is located approximately north of San Francisco, is located on the Lost Coast entirely within Humboldt County, California, United States. At 124° 24' 34" W longitude ...

, Northern California, passing through

Oregon Oregon () is a state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington, while the Snake River delineates much of its eastern boundary with Idaho. T ...

and Washington, and terminating at about Vancouver Island in

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, ...

. The Explorer, Juan de Fuca, and Gorda plates are some of the remnants of the vast ancient

Farallon Plate The Farallon Plate was an ancient oceanic plate. It formed one of the three main plates of Panthalassa, alongside the Phoenix Plate and Izanagi Plate, which were connected by a triple junction. The Farallon Plate began subducting under the west ...

which is now mostly subducted under the North American Plate. The North American Plate itself is moving slowly in a generally southwest direction, sliding over the smaller plates as well as the huge oceanic Pacific Plate (which is moving in a northwest direction) in other locations such as the

San Andreas Fault The San Andreas Fault is a continental transform fault that extends roughly through California. It forms the tectonic boundary between the Pacific Plate and the North American Plate, and its motion is right-lateral strike-slip (horizonta ...

in central and southern California. Tectonic processes active in the Cascadia subduction zone region include accretion, subduction, deep earthquakes, and active volcanism of the Cascades. This volcanism has included such notable eruptions as

Mount Mazama Mount Mazama (''Giiwas'' in the Native American language Klamath) is a complex volcano in the state of Oregon, United States, in a segment of the Cascade Volcanic Arc and Cascade Range. Most of the mountain collapsed following a major erupt ...

(

Crater Lake Crater Lake ( 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 lake partly fill ...

) about 7,500 years ago, the

Mount Meager massif The Mount Meager massif is a group of volcanic peaks in the of the Coast Mountains in southwestern British Columbia, Canada. Part of the Cascade Volcanic Arc of western North America, it is located north of Vancouver at the northern end of the P ...

( Bridge River Vent) about 2,350 years ago, 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 ...

in 1980. USGS Major cities affected by a disturbance in this subduction zone include Vancouver and

Victoria Victoria most commonly refers to: * Victoria (Australia), a state of the Commonwealth of Australia * Victoria, British Columbia, provincial capital of British Columbia, Canada * Victoria (mythology), Roman goddess of Victory * Victoria, Seychelle ...

, British Columbia;

Seattle Seattle ( ) is a seaport city on the West Coast of the United States. It is the seat of King County, Washington. With a 2020 population of 737,015, it is the largest city in both the state of Washington and the Pacific Northwest regio ...

, Washington; and Portland, Oregon.

History

Tradition

There are no contemporaneous written records of the 1700 Cascadia earthquake. Orally transmitted legends from the Olympic Peninsula area tell of an epic battle between a thunderbird and a whale. In 2005, seismologist Ruth Ludwin set out to collect and analyze anecdotes from various

First Nations First Nations or first peoples may refer to: * Indigenous peoples, for ethnic groups who are the earliest known inhabitants of an area. Indigenous groups *First Nations is commonly used to describe some Indigenous groups including: **First Natio ...

groups. Reports from the Huu-ay-aht,

Makah The Makah (; Klallam: ''màq̓áʔa'')Renker, Ann M., and Gunther, Erna (1990). "Makah". In "Northwest Coast", ed. Wayne Suttles. Vol. 7 of '' Handbook of North American Indians'', ed. William C. Sturtevant. Washington, D.C.: Smithsonian Instit ...

, Hoh, Quileute, Yurok, and Duwamish peoples referred to earthquakes and saltwater floods. This collection of data allowed the researchers to come up with an estimated date range for the event; the midpoint was in the year 1701.

Ghost forests

During low tide one day in March 1986, paleogeologist Brian Atwater dug along

Neah Bay Neah Bay is a census-designated place (CDP) on the Makah Reservation in Clallam County, Washington, United States. The population was 865 at the 2010 census. It is across the Canada–US border from British Columbia. Originally called "Scarboro ...

with a ''nejiri gama'', a small hand hoe. Under a top layer of sand, he uncovered a distinct plant— arrowgrass—that had grown in a layer of marsh soil. This finding was evidence that the ground had suddenly sunk under sea level, causing saltwater to kill the vegetation. The event had happened so quickly that the top layer of sand sealed away the air, thus preserving centuries-old plants. In 1987, Atwater mounted another expedition paddling up the Copalis River with Dr. David Yamaguchi, who was then studying the eruptions of

. The pair happened upon a section of " ghost forest", so-called due to the dead, gray stumps left standing after a sudden inundation of salt water had killed them hundreds of years ago. Originally thought to have died slowly due to a gradual rise in sea level, closer inspection yielded a different story: the land plummeted up to two meters during an earthquake. Having initially tested spruce using tree-ring dating, they found that the stumps were too rotted to count all the outer rings. However, upon having examined those of the

western red cedar ''Thuja plicata'' is an evergreen coniferous tree in the cypress family Cupressaceae, native to western North America. Its common name is western redcedar (western red cedar in the UK), and it is also called Pacific redcedar, giant arborvitae ...

and comparing them to the living specimens meters away from the banks, they were able to approximate their year of death. There were rings up until the year 1699, indicating that the incident had occurred shortly thereafter. Root samples confirmed their conclusion, narrowing the time frame to the winter of 1699 to 1700. As with the arrowgrass site, the banks of the Copalis River are lined with a layer of marsh followed by a layer of sand. Jody Bourgeois and her team went on to demonstrate that the sand cover had originated with a tsunami surge rather than a storm surge. In 1995, an international team led by Alan Nelson of the USGS further corroborated these findings with 85 new samples from the rest of the

Pacific Northwest The Pacific Northwest (sometimes Cascadia, or simply abbreviated as PNW) is a geographic region in western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Tho ...

. All along British Columbia, Washington State, and Oregon, the coast had fallen due to a violent earthquake and been covered by sand from the subsequent tsunami. A further ghost forest was identified by Gordon Jacoby, a dendrochronologist from Columbia University, underwater in Lake Washington. Unlike the other trees, these suffered from a landslide rather than a dip in the fault during a separate event around 900 CE.

Activity

In the 1960s, underground fractures were uncovered by oil companies in Puget Sound. These were believed to be inactive through the 1990s. In the 1980s, geophysicists

Tom Heaton Thomas David Heaton (born 15 April 1986) is an English professional footballer who plays as a goalkeeper for club Manchester United. Heaton began his career in the Manchester United academy but was unable to break into the first team and sp ...

and

Hiroo Kanamori is a Japanese seismologist who has made fundamental contributions to understanding the physics of earthquakes and the tectonic processes that cause them. Career Kanamori and American seismologist Thomas C. Hanks developed the moment magnitud ...

of Caltech compared the generally quiet Cascadia to more active subduction zones elsewhere in the Ring of Fire. They found similarities to faults in Chile, Alaska, and Japan's Nankai Trough, locations known for

megathrust earthquake Megathrust earthquakes occur at convergent plate boundaries, where one tectonic plate is forced underneath another. The earthquakes are caused by slip along the thrust fault that forms the contact between the two plates. These interplate earthqu ...

s, a conclusion that was met with skepticism from other geophysicists at the time.

Orphan tsunami

A 1996 study published by seismologist

Kenji Satake Kenji Satake is a Japanese seismologist who has made significant contributions to subduction and tsunami research. Along with Brian Atwater and David Yamaguchi, Satake assembled disparate pieces of information regarding a Japanese tsunami that h ...

supplemented the research by Atwater et al. with tsunami evidence across the Pacific. Japanese annals, which have recorded natural disasters since approximately 600 CE, had reports of a sixteen-foot tsunami that struck the coast of Honshu Island during the

Genroku was a after Jōkyō and before Hōei. The Genroku period spanned the years from the ninth month of 1688 to the third month of 1704. The reigning emperor was .Titsingh, Isaac. (1834). ''Annales des empereurs du japon'', p. 415. The period w ...

. Since no earthquake had been observed to produce it, scholars dubbed it an "orphan tsunami." Translating the Japanese calendar, Satake found the incident had taken place around midnight of 27–28 January 1700, ten hours after the earthquake occurred. The original magnitude 9.0 earthquake in the Pacific Northwest had thus occurred around 9pm local time on 26 January 1700.

Geophysics

The Cascadia Subduction Zone (CSZ) is a long dipping fault that stretches from Northern Vancouver Island to

in northern California. It separates the Juan de Fuca and North America plates. New Juan de Fuca plate is created offshore along the

Juan de Fuca Ridge The Juan de Fuca Ridge is a mid-ocean spreading center and divergent plate boundary located off the coast of the Pacific Northwest region of North America. The ridge separates the Pacific Plate to the west and the Juan de Fuca Plate to the east ...

. USGS The Juan de Fuca plate moves toward, and eventually is shoved beneath, the continent (North American plate). The zone separates the Juan de Fuca Plate,

Explorer Plate The Explorer Plate is an oceanic tectonic plate beneath the Pacific Ocean off the west coast of Vancouver Island, Canada, which is partially subducted under the North American Plate. Along with the Juan de Fuca Plate and Gorda Plate, the Explor ...

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 (by, for example, publications from the USGS Earthquake Hazards Program) a ...

, and North American Plate. Here, the oceanic crust of the Pacific Ocean has been sinking beneath the continent for about 200 million years, and currently does so at a rate of approximately 40 mm/ yr. At depths shallower than or so, the Cascadia zone is locked by friction while stress slowly builds up as the subduction forces act, until the fault's frictional strength is exceeded and the rocks slip past each other along the fault in a

. Below the plate interface exhibits episodic tremor and slip. The width of the Cascadia subduction zone varies along its length, depending on the angle of the subducted oceanic plate, which heats up as it is pushed deeper beneath the continent. As the edge of the plate sinks and becomes hotter and more molten, the subducting rock eventually loses the ability to store mechanical stress; earthquakes may result. On the Hyndman and Wang diagram (not shown, click on reference link below) the "locked" zone is storing up energy for an earthquake, and the "transition" zone, although somewhat plastic, could probably rupture. The Cascadia subduction zone runs from triple junctions at its north and south ends. To the north, just below

Haida Gwaii Haida Gwaii (; hai, X̱aaydag̱a Gwaay.yaay / , literally "Islands of the Haida people") is an archipelago located between off the northern Pacific coast of Canada. The islands are separated from the mainland to the east by the shallow Heca ...

, it intersects the Queen Charlotte Fault and the Explorer Ridge. To the south, just off Cape Mendocino in California, it intersects the

and the

Mendocino Fracture Zone The Mendocino Fracture Zone is a fracture zone and transform boundary over 4000 km (2500 miles) long, starting off the coast of Cape Mendocino in far northern California. It runs westward from a triple junction with the San Andreas Fault a ...

at the Mendocino Triple Junction.

Recent seismicity

Subduction zones experience various types of earthquakes (or seismicity); including

slow earthquake A slow earthquake is a discontinuous, earthquake-like event that releases energy over a period of hours to months, rather than the seconds to minutes characteristic of a typical earthquake. First detected using long term strain measurements, most ...

s, interplate earthquakes, and intraplate earthquakes. Unlike other subduction zones on Earth, Cascadia presently experiences low levels of seismicity and has not generated a

since January 26, 1700. Despite low levels of seismicity compared to other subduction zones, Cascadia hosts various types of earthquakes that are recorded by seismic and

geodetic Geodesy ( ) is the Earth science of accurately measuring and understanding Earth's figure (geometric shape and size), orientation in space, and gravity. The field also incorporates studies of how these properties change over time and equivale ...

instruments, such as

seismometer A seismometer is an instrument that responds to ground noises and shaking such as caused by earthquakes, volcanic eruptions, and explosions. They are usually combined with a timing device and a recording device to form a seismograph. The outpu ...

s and GNSS receivers. Tremor, a type of slow fault slip, occurs along almost the entire length of Cascadia at regular intervals of 13–16 months. Tremor occurs deeper on the subduction interface than the locked area where megathrust earthquakes occur. The depth of tremor along the subduction interface in Cascadia ranges from 28 km to 45 km, and the motion is so slow that it is not felt at the surface by people or animals, but it can be measured geodetically. The highest density of tremor activity in Cascadia occurs from northern Washington into southern Vancouver Island, and in northern California. Tremor in Cascadia is monitored by the Pacific Northwest Seismic Network's semi-automatic tremor detection system. The majority of interplate earthquakes, or earthquakes that occur near the boundaries of tectonic plates, near the Cascadia subduction zone occur in the forearc of the overriding North American Plate in Washington, west 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 ...

and east of where tremor occurs. These earthquakes are sometimes referred to as crustal earthquakes, and they are capable of causing significant damage due to their relatively shallow depths. A damaging magnitude 7 interplate earthquake occurred on the

Seattle Fault The Seattle Fault is a zone of multiple shallow east–west thrust faults that cross the Puget Sound Lowland and through Seattle (in the U.S. state of Washington) in the vicinity of Interstate Highway 90. The Seattle Fault was first recognized as ...

around 900–930 CE that generated 3 meters of uplift and a 4-5 meter tsunami. A substantial number of forearc interplate earthquakes also occur in northern California. Much less interplate seismicity occurs in Oregon compared to Washington and northern California, although Oregon hosts more

volcanic activity 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 a ...

than its neighboring states. Intraslab earthquakes, frequently associated with stresses within the subducting plate in convergent margins, occur most frequently in northern Cascadia along the west coast of Vancouver Island and in Puget Sound, and in southern Cascadia within the subducting

, near the Mendocino Triple Junction offshore of northern California. The

1949 Olympia earthquake The 1949 Olympia earthquake occurred on April 13 at with a moment magnitude of 6.7 and a maximum Mercalli Intensity of VIII (''Severe''). The shock was located in the area between Olympia and Tacoma, and was felt throughout the state, as wel ...

was a damaging magnitude 6.7 intraslab earthquake that occurred at 52 km depth and caused 8 deaths. Another notable intraslab earthquake in the Puget Sound region was the magnitude 6.8 2001 Nisqually earthquake. Intraslab earthquakes in Cascadia occur in areas where the subducting plate has high curvature. Much of the seismicity that occurs off the coast of northern California is due to

intraplate deformation Intraplate deformation is the folding, breaking, or flow of the Earth's crust within plates instead of at their margins. This process usually occurs in areas with especially weak crust and upper mantle, such as the Tibetan Plateau (Figure 1). Int ...

within the

. Similar to the distribution of interplate earthquakes in Cascadia, intraslab earthquakes are infrequent in Oregon, with its strongest earthquake since statehood being the 5.6 magnitude 1993 Scotts Mills earthquake, an oblique-slip quake.

Megathrust earthquakes

Earthquake effects

Megathrust earthquake Megathrust earthquakes occur at convergent plate boundaries, where one tectonic plate is forced underneath another. The earthquakes are caused by slip along the thrust fault that forms the contact between the two plates. These interplate earthqu ...

s are the most powerful earthquakes known to occur, and can exceed

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 ...

9.0, which releases 1,000 times more energy than magnitude 7.0 and 1 million times more energy than a magnitude 5.0. They occur when enough energy (stress) has accumulated in the "locked" zone of the fault to cause a rupture. The magnitude of a megathrust earthquake is proportional to length of the rupture along the fault. The Cascadia Subduction Zone, which forms the boundary between the Juan de Fuca and North American plates, is a very long sloping fault that stretches from mid-Vancouver Island to Northern California. Because of the great length of the fault, the Cascadia Subduction Zone is capable of producing very large earthquakes if rupture occurs along its entire length. Thermal and deformation studies indicate that the region 60 kilometers (about 40 miles) downdip (east) of the deformation front (where plate deformation begins) is fully locked (the plates do not move past each other). Further downdip, there is a transition from fully locked to aseismic sliding. In 1999, a group of Continuous

Global Positioning System The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite sy ...

sites registered a brief reversal of motion of approximately 2 centimeters (0.8 inches) over a 50 kilometer by 300 kilometer (about 30 mile by 200 mile) area. The movement was the equivalent of a 6.7 magnitude earthquake. The motion did not trigger an earthquake and was only detectable as silent, non-earthquake seismic signatures. In 2004, a study conducted by the Geological Society of America analyzed the potential for land subsidence along the Cascadia subduction zone. It postulated that several towns and cities on the west coast of Vancouver Island, such as

Tofino Tofino ( ) is a town of approximately 2,516 residents on the west coast of Vancouver Island in the Canadian province of British Columbia. The District of Tofino is located at the western terminus of Highway 4 on the tip of the Esowista Peninsu ...

and

Ucluelet Ucluelet (, also Ukee) is a district municipality (population 1,717) on the Ucluelet Peninsula on the west coast of Vancouver Island in British Columbia, Canada. Ucluelet means "people of the safe harbour" in the indigenous Nuu-chah-nulth (No ...

, are at risk for a sudden, earthquake initiated, 1–2 m subsidence.

San Andreas Fault connection

Studies of past earthquake traces on both the northern

and the southern Cascadia subduction zone indicate a correlation in time which may be evidence that quakes on the Cascadia subduction zone may have triggered most of the major quakes on the northern San Andreas during at least the past 3,000 years or so. The evidence also shows the rupture direction going from north to south in each of these time-correlated events. The 1906 San Francisco earthquake seems to have been a major exception to this correlation, however, as it was not preceded by a major Cascadia quake.

Earthquake timing

The last known great earthquake in the northwest was the 1700 Cascadia earthquake, years ago.

Geological Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other E ...

evidence indicates that great earthquakes (> magnitude 8.0) may have occurred sporadically at least seven times in the last 3,500 years, suggesting a return time of about 500 years. Seafloor core evidence indicates that there have been forty-one subduction zone earthquakes on the Cascadia subduction zone in the past 10,000 years, suggesting a general average earthquake recurrence interval of only 243 years. Of these 41, nineteen have produced a "full margin rupture", wherein the entire fault opens up. By comparison, similar subduction zones in the world usually have such earthquakes every 100 to 200 years; the longer interval here may indicate unusually large stress buildup and subsequent unusually large earthquake slip. There is also evidence of accompanying

tsunami A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater exp ...

s with every earthquake. One strong line of evidence for these earthquakes is convergent timings for fossil damage from tsunamis in the

and historical Japanese records of tsunamis. USGS Professional Paper 1707 The next rupture of the Cascadia Subduction Zone is anticipated to be capable of causing widespread destruction throughout the

Forecasts of the next major earthquake

Prior to the 1980s, scientists thought that the subduction zone did not generate earthquakes like other subduction zones around the world, but research by Brian Atwater and

tied together evidence of a large tsunami on the Washington coast with documentation of an orphan tsunami in Japan (a tsunami without an associated earthquake). The two pieces of the puzzle were linked, and they then realized that the subduction zone was more hazardous than previously suggested. In 2009, some geologists predicted a 10% to 14% probability that the Cascadia Subduction Zone will produce an event of magnitude 9.0 or higher in the next 50 years. In 2010, studies suggested that the risk could be as high as 37% for earthquakes of magnitude 8.0 or higher. Geologists and civil engineers have broadly determined that the Pacific Northwest region is not well prepared for such a colossal earthquake. The earthquake is expected to be similar to the 2011 Tōhoku earthquake and tsunami, because the rupture is expected to be as long as the 2004 Indian Ocean earthquake and tsunami. The resulting

might reach heights of approximately 30 meters (100 ft). FEMA estimates some 13,000 fatalities from such an event, with another 27,000 injured, which would make it the deadliest natural disaster in American, and North American, history. FEMA further predicts that a million people will be displaced, with yet another 2.5 million requiring food and water. An estimated 1/3 of public safety workers will not respond to the disaster due to a collapse in infrastructure and a desire to ensure the safety of themselves and their loved ones. Other analyses predict that even a magnitude 6.7 earthquake in Seattle would result in 7,700 dead and injured, $33 billion in damage, 39,000 buildings severely damaged or destroyed, and 130 simultaneous fires.

Cascade Volcanic Arc

The Cascade Volcanic Arc is a continental volcanic arc that extends from northern

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...

to the coastal peninsula of Alaska. The arc consists of a series of Quaternary age stratovolcanoes that grew on top of pre-existing geologic materials that ranged from

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

volcanics to

glacial ice A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires distinguishing features, such as ...

. The Cascade Volcanic arc is located approximately 100 km inland from the coast, and forms a north-to-south chain of peaks that average over 3,000 m (10,000 ft) in elevation. The major peaks from south to north include: *

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 ...

and Mount Shasta (California) *

(Mazama), Three Sisters, Mount Jefferson, Mount Hood (Oregon) * Mount Adams,

, Mount Rainier,

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 ...

, Mount Baker (Washington) * Mount Garibaldi and

(British Columbia) The most active volcanoes in the chain include Mount St. Helens, Mount Baker, Lassen Peak, Mount Shasta, and Mount Hood. Mount St. Helens captured worldwide attention when it erupted catastrophically in 1980. St. Helens continues to rumble, albeit more quietly, emitting occasional steam plumes and experiencing small earthquakes, both signs of continuing magmatic activity. Most of the volcanoes have a main, central vent from which the most recent eruptions have occurred. The peaks are composed of layers of solidified

andesitic 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 predomin ...

dacitic 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 rhyol ...

magma, and the more siliceous (and explosive) rhyolite.

Volcanoes above the subduction zone

The volcanoes above the subduction zone include: *

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 cald ...

* Mount Cayley * Mount Garibaldi * Mount Baker *

* Mount Rainier *

* Mount Adams * Mount Hood * Mount Jefferson * Three Sisters *

Newberry Volcano Newberry Volcano is a large active shield-shaped stratovolcano located about south of Bend, Oregon, United States, east of the major crest of the Cascade Range, within the Newberry National Volcanic Monument. Its highest point is Paulina Peak ...

(Crater Lake) * Mount McLoughlin * Medicine Lake Volcano * Mount Shasta *

* Black Butte

References

Central Washington University Central Washington University (CWU) is a public university in Ellensburg, Washington. Founded in 1891, the university consists of four divisions: the President's Division, Business and Financial Affairs, Operations, and Academic and Student Lif ...

Toast, tsunamis and the really big one , Chris Goldfinger , TEDxMtHood
– TEDx {{Authority control Subduction zones Geology of Oregon Geology of Washington (state) Geologic provinces of California Geology of British Columbia Natural hazards in British Columbia Seismic zones of British Columbia Cascade Volcanoes