Juan de Fuca Plate

The Juan de Fuca Plate is a tectonic plate generated from the Juan de Fuca Ridge that is subducting under the northerly portion of the western side of the North American Plate at the Cascadia subduction zone. It is named after the explorer of the same name. One of the smallest of Earth's tectonic plates, the Juan de Fuca Plate is a remnant part of the once-vast Farallon Plate, which is now largely subducted underneath the North American Plate.

Juan de Fuca Plate
The Juan de Fuca Plate
TypeMinor
Approximate area250,000 km2 (96,000 sq mi)[1]
Movement1north-east
Speed126 mm/year (1.0 in/yr)
FeaturesPacific Ocean
1Relative to the African Plate
JuandeFucasubduction
Cutaway of the Juan de Fuca Plate. USGS image

Origins

The Juan de Fuca Plate system has its origins with Panthalassa's oceanic basin and crust. This oceanic crust has primarily been subducted under the North American Plate, and the Eurasian Plate. Panthalassa's oceanic plate remnants are understood to be the Juan de Fuca, Gorda, Cocos and the Nazca plates, all four of which were part of the Farallon Plate.

Extent

Juan de fuca plate
A map of the Juan de Fuca Plate

The Juan de Fuca Plate is bounded on the south by the Blanco Fracture Zone (running northwest off the coast of Oregon), on the north by the Nootka Fault (running southwest off Nootka Island, near Vancouver Island, British Columbia) and along the west by the Pacific Plate (which covers most of the Pacific Ocean and is the largest of Earth's tectonic plates). The Juan de Fuca Plate itself has since fractured into three pieces, and the name is applied to the entire plate in some references, but in others only to the central portion. The three fragments are differentiated as such: the piece to the south is known as the Gorda Plate and the piece to the north is known as the Explorer Plate. The separate pieces are demarcated by the large offsets of the undersea spreading zone.

Volcanism

This subducting plate system has formed the Cascade Range, the Cascade Volcanic Arc, and the Pacific Ranges, along the west coast of North America from southern British Columbia to northern California. These in turn are part of the Pacific Ring of Fire, a much larger-scale volcanic feature that extends around much of the rim of the Pacific Ocean.

Earthquakes

The last megathrust earthquake at the Cascadia subduction zone was the 1700 Cascadia earthquake, estimated to have a moment magnitude of 8.7 to 9.2. Based on carbon dating of local tsunami deposits, it is inferred to have occurred around 1700.[2] Evidence of this earthquake is also seen in the ghost forest along the bank of the Copalis River in Washington. The rings of the dead trees indicate that they died around 1700, and it is believed that they were killed when the earthquake occurred and sank the ground beneath them causing the trees to be flooded by saltwater.[3] Japanese records indicate that a tsunami occurred in Japan on 26 January 1700, which was likely caused by this earthquake.[4]

In 2008, small earthquakes were observed within the Juan de Fuca Plate. The unusual quakes were described as "more than 600 quakes over the past 10 days in a basin 150 miles [240 km] southwest of Newport". The quakes were unlike most quakes in that they did not follow the pattern of a large quake, followed by smaller aftershocks; rather, they were simply a continual deluge of small quakes. Furthermore, they did not occur on the tectonic plate boundary, but rather in the middle of the plate. The subterranean quakes were detected on hydrophones, and scientists described the sounds as similar to thunder, and unlike anything previously recorded.[5]

Carbon sequestration potential

The basaltic formations of the Juan de Fuca Plate could potentially be suitable for long-term CO2 sequestration as part of a carbon capture and storage (CCS) system. Injection of CO2 would lead to the formation of stable carbonates. It is estimated that 100 years of US carbon emissions (at current rate) could be stored securely, without risk of leakage back into the atmosphere.[6][7]

Tearing

In 2019, scientists from the University of California, Berkeley published a study in Geophysical Research Letters in which they reported that by utilizing data from over 30,000 seismic waves and 217 earthquakes to create a three-dimensional map, they had revealed the existence of a hole in the subducted part of the Juan de Fuca Plate, and speculated that the hole is an indication of a 150 kilometres (93 mi) deep tear in the plate along a "preexisting zone of weakness." According to William B. Hawley and Richard M Allen, the authors of the study, the hole may be the cause of volcanism and earthquakes on the plate, and is causing deformation of the offshore part of the plate. The deformation may cause the plate to fragment, with the remaining un-subducted small pieces becoming attached to other plates nearby.[8][9]

See also

References

  1. ^ "Sizes of Tectonic or Lithospheric Plates". Geology.about.com. 2014-03-05. Retrieved 2016-01-06.
  2. ^ Wong, Florence L. "Seaside, Oregon, Tsunami Pilot Study GIS, USGS Data Series 236, home page". pubs.usgs.gov. Retrieved 2017-04-15.
  3. ^ Schulz, Kathryn (June 20, 2015). "The Earthquake That Will Devastate the Pacific Northwest". The New Yorker.
  4. ^ Satake, Kenji; Wang, Kelin; Atwater, Brian F. (2003-11-01). "Fault slip and seismic moment of the 1700 Cascadia earthquake inferred from Japanese tsunami descriptions". Journal of Geophysical Research: Solid Earth. 108 (B11): 2535. Bibcode:2003JGRB..108.2535S. doi:10.1029/2003JB002521. ISSN 2156-2202.
  5. ^ "Unusual Earthquake Swarm Off Oregon Coast Puzzles Scientists". Science News. ScienceDaily. 2008-04-14.
  6. ^ Goldberg, D. S. (2008-07-22). "Carbon dioxide sequestration in deep-sea basalt". Proceedings of the National Academy of Sciences. 105 (29): 9920–9925. Bibcode:2008PNAS..105.9920G. doi:10.1073/pnas.0804397105. PMC 2464617. PMID 18626013.
  7. ^ Fairley, Jerry (January 2013). "Sub-seafloor Carbon Dioxide Storage Potential on the Juan de Fuca Plate, Western North America". Energy Procedia. 37: 5248–5257. doi:10.1016/j.egypro.2013.06.441.
  8. ^ Hawley William B. and Allen, Richard M. (July 3, 2019) "The Fragmented Death of the Farallon Plate" Geophysical Research Letters
  9. ^ Nield, David (July 31, 2019) "A Tectonic Plate Under Oregon Is Being Slowly Ripped Apart" Science Alert

External links

1700 Cascadia earthquake

The 1700 Cascadia earthquake occurred along the Cascadia subduction zone on January 26 with an estimated moment magnitude of 8.7–9.2. The megathrust earthquake involved the Juan de Fuca Plate from mid-Vancouver Island, south along the Pacific Northwest coast as far as northern California. The length of the fault rupture was about 1,000 kilometers (620 miles), with an average slip of 20 meters (66 ft).

The earthquake caused a tsunami which struck the coast of Japan and may also be linked to the Bonneville Slide and the Tseax Cone eruption in British Columbia.

1918 Vancouver Island earthquake

The 1918 Vancouver Island earthquake occurred in British Columbia, Canada at 12:41 a.m. Pacific Standard Time on December 6.

The earthquake was most likely of the strike-slip type, and was estimated to have a maximum perceived intensity of VII (Very strong) on the Mercalli intensity scale. The epicenter was located east of the Stewardson inlet on the west coast of Vancouver Island, with damage occurring at the Estevan Point lighthouse on the Hesquiat Peninsula. The event registered 7.2 on the moment magnitude scale and was felt as far as northern Washington state and the interior of British Columbia.

The earthquake took place in the vicinity of the Cascadia subduction zone where the Juan de Fuca Plate and the Explorer Plate are being subducted under the North American Plate at a rate of 4 centimeters (1.6 in) and less than 2 centimeters (0.79 in) per year respectively, but the event was a crustal intraplate earthquake and was produced from the complicated interaction between the plates in the area. The source of the earthquake was the Nootka transform fault, which separates the Juan de Fuca and Explorer plates and has been the origin of at least five additional moderate to large events since 1918.

2013 Vancouver Whitecaps FC season

The 2013 Vancouver Whitecaps FC season was the Whitecaps' third season in Major League Soccer, the top tier of soccer in the United States and Canada.

Explorer Plate

The Explorer Plate is an oceanic tectonic plate beneath the Pacific Ocean off the west coast of Vancouver Island, Canada and is partially subducted under the North American Plate. Along with the Juan De Fuca Plate and Gorda Plate, the Explorer Plate is a remnant of the ancient Farallon Plate which has been subducted under the North American Plate. The Explorer Plate separated from the Juan De Fuca Plate roughly 4 million years ago. In its smoother, southern half, the average depth of the Explorer plate is roughly 2,400 metres (7,900 ft) and rises up in its northern half to a highly variable basin between 1,400 metres (4,600 ft) and 2,200 metres (7,200 ft) in depth.

Explorer Ridge

The Explorer Ridge is a mid-ocean ridge, a divergent tectonic plate boundary located about 241 km (150 mi) west of Vancouver Island, British Columbia, Canada. It lies at the northern extremity of the Pacific spreading axis. To its east is the Explorer Plate, which together with the Juan de Fuca Plate and the Gorda Plate to its south, is what remains of the once-vast Farallon Plate which has been largely subducted under the North American Plate. The Explorer Ridge consists of one major segment, the Southern Explorer Ridge, and several smaller segments. It runs northward from the Sovanco Fracture Zone to the Queen Charlotte Triple Junction, a point where it meets the Queen Charlotte Fault and the northern Cascadia subduction zone.

Farallon Trench

The Farallon Trench was a subduction related tectonic formation located off the coast of the western California continental margin during the late to mid Cenozoic era, around 50 miles southeast of modern-day Monterey Bay. The time duration of subduction began from around 165 Ma when the Farallon Plate replaced the Mezczlera promontory, until the San Andreas Fault straightening around 35 Ma. As data accumulated over time, a common view developed that one large oceanic plate, the Farallon Plate, acted as a conveyor belt, conveying accreted terranes onto the North American west coast. As the continent overran the subducting Farallon Plate, the denser plate became subducted into the mantle below the continent. When the plates converged, the dense oceanic plate sank into the mantle to form a slab below the lighter continent. Rapid subduction under the southwestern North America continent began 40 to 60 million years ago (Ma), during the mid Paleocene to mid Eocene epochs. This convergent subduction margin created a distinctive geomorphologic feature called an oceanic trench, which occurs at a convergent plate boundaries as a heavy metal rich, lithospheric plate moves below a light silica rich continental plate. The trench marks the position at which the flexed subducting slab begins to descend beneath and deform the continental plate margin. By 43 Ma, during the Eocene, worldwide plate motions changed and the Pacific Plate began to move away from North America and subduction of the Farallon Plate slowed dramatically. By around 36 Ma, the easternmost part of the East Pacific Rise, located between the Pioneer and Murray fracture zones at that time, approached the trench and the young, hot, buoyant lithosphere appears to have clogged part of the subduction zone, resulting in widespread dramatic uplift on land. The eventual complete subduction of this plate, consequential contact of the Pacific Plate with the California continental margin, and creation of the Mendocino Triple Junction (MTJ), took place around 30 to 20 Ma. The partial complete subduction and division of the Farallon Plate by the Pacific Plate, created the Juan de Fuca Plate to the north and the Cocos Plate to the south. The final stages of the evolution of California's continental margin was the growth of the San Andres transform fault system, which formed as the Pacific Plate came into contact with the continental margin and the MTJ was formed. As subduction of the Pacific Plate continued along this margin, and the contact zone grew, the San Andres proportionally grew as well.

Geology of the Pacific Northwest

The geology of the Pacific Northwest includes the composition (including rock, minerals, and soils), structure, physical properties and the processes that shape the Pacific Northwest region of the United States and Canada. The region is part of the Ring of Fire: the subduction of the Pacific and Farallon Plates under the North American Plate is responsible for many of the area's scenic features as well as some of its hazards, such as volcanoes, earthquakes, and landslides.

The geology of the Pacific Northwest is vast and complex. Most of the region began forming about 200 million years ago as the North American Plate started to drift westward during the rifting of Pangaea. Since that date, the western edge of North America has grown westward as a succession of island arcs and assorted ocean-floor rocks have been added along the continental margin.

There are at least five geologic provinces in the area: the Cascade Volcanoes, the Columbia Plateau, the North Cascades, the Coast Mountains, and the Insular Mountains. The Cascade Volcanoes are an active volcanic region along the western side of the Pacific Northwest. The Columbia Plateau is a region of subdued geography that is inland of the Cascade Volcanoes, and the North Cascades are a mountainous region in the northwest corner of the United States, extending into British Columbia. The Coast Mountains and Insular Mountains are a strip of mountains along the coast of British Columbia, each with its own geological history.

Goat Rocks

Goat Rocks is an extinct stratovolcano in the Cascade Range, located between Mount Rainier and Mount Adams in southern Washington, in the United States. Part of the Cascade Volcanoes, it was formed by the subduction of the Juan de Fuca Plate under the western edge of the North American Plate. The volcano was active from 3.2 million years ago until eruptions ceased between 1 and 0.5 million years ago. Throughout its complex eruptive history, volcanism shifted from silicic explosive eruptions to voluminous, mafic activity.

The volcano and the surrounding Goat Rocks Wilderness, established in 1964, are named after the numerous mountain goats which live in the area. The variable climate of the wilderness area supports a host of wildlife, including marmots, pikas, deer, and elk. Various peaks within the wilderness can be climbed or scrambled, and other activities such as hiking are permitted. The area is rife with minerals and resources, including coal, cobalt, copper, and base metals.

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) as simply the southernmost portion of the neighboring Juan de Fuca Plate, another Farallon remnant.

Unlike most tectonic plates, the Gorda Plate experiences significant intraplate deformation inside its boundaries. Numerous faults have been mapped in both the sediments and basement of the Gorda Basin, which is in the interior of the plate south of 41.6°N. Stresses from the neighboring North American Plate and Pacific Plate cause frequent earthquakes in the interior of the plate, including the 1980 Eureka earthquake (also known as the Gorda Basin event).The easterly side is a convergent boundary subducting under the North American Plate in northern California. The southerly side is a transform boundary with the Pacific Plate along the Mendocino Fault. The westerly side is a divergent boundary with the Pacific Plate forming the Gorda Ridge. This ridge provides morphological evidence of differing spreading rates, with the northern portion of the ridge being narrow, and the southern portion being wide. The northerly side is a transform boundary with the Juan de Fuca Plate, the Blanco Fracture Zone.

The subducting Gorda Plate is connected with the volcanoes in northern California, namely, Mount Shasta and Lassen Peak. Lassen Peak last erupted in 1914–1917.

Gorda Ridge

The Gorda Ridge (41°36'19.6"N 127°22'03.1"W), a tectonic spreading center, is located roughly 200 kilometres (120 mi) off the northern coast of California and southern Oregon. Running NE – SW it is roughly 300 kilometres (190 mi) in length. The ridge is broken into three segments; the northern ridge, central ridge, and the southern ridge, which contains the Escanaba Trough.

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. It runs generally northward, with a length of approximately 500 kilometers (300 miles). The ridge is a section of what remains from the larger Pacific-Farallon Ridge which used to be the primary spreading center of this region, driving the Farallon Plate underneath the North American Plate through the process of plate tectonics. Today, the Juan de Fuca Ridge pushes the Juan de Fuca Plate underneath the North American plate, forming the Cascadia Subduction Zone.

Mount Thielsen

Mount Thielsen, or Big Cowhorn (Klamath: hisc’akwaleeʔas), is an extinct shield volcano in the Oregon High Cascades, near Mount Bailey. Because eruptive activity ceased 250,000 years ago, glaciers have heavily eroded the volcano's structure, creating precipitous slopes and a horn-like peak. The spire-like shape of Thielsen attracts lightning strikes and creates fulgurite, an unusual mineral. The prominent horn forms a centerpiece for the Mount Thielsen Wilderness, a reserve for recreational activities such as skiing and hiking.

Thielsen was produced by subduction of the Juan de Fuca Plate under the North American Plate. Volcanism near the Cascades dates back to 55 million years ago (mya), and extends from British Columbia to California. Thielsen is part of the High Cascades, a branch of the main Cascades range that includes several Oregon volcanoes less than 3.5 million years old; it is also a member of a group of extinct volcanoes distinguished by their sharp peaks.

The area surrounding the volcano was originally inhabited by Chinook Native Americans, and was later encountered by Polish settlers. One of the visitors was Jon Hurlburt, an early explorer of the area who named the volcano after the engineer Hans Thielsen. Later explorers discovered nearby Crater Lake. The volcano was not analyzed until 1884, when a team from the United States Geological Survey sampled its fulgurite deposits.

Neenach Volcano

Neenach Volcano is an extinct Miocene volcano in the Coastal Ranges of California. After formation, the volcanic field was split by a fault in the San Andreas Fault Zone, and over the last 23 million years, the two halves of the volcano have moved about 195 miles (314 kilometers) apart.

The correlation of the two portions, now called the Pinnacles and Neenach volcanic formations, is significant; this correlation has become a “classic example” of plate tectonics for the scientific community. Ten rock types with nearly identical field, petrographic, and chemical characteristics are present in each formation in essentially the same stratigraphic order. This provides ample evidence for the correlation and interpreted movement along the San Andreas Fault.

The volcano formed 23 million years ago during tectonic subduction of the oceanic Juan de Fuca Plate beneath the continental North American Plate, a process often associated with volcanic eruptions near the plate boundaries. Subsequent complex geophysical mechanisms caused a segment of the Juan de Fuca Plate to fuse to the eastern edge of the adjoining Pacific Plate, ending subduction and initiating horizontal shear movement between the plates, with the Pacific Plate moving northwesterly and the North American Plate moving in the opposite southeast direction. This transform movement began approximately 20 million years ago and the resultant shear lineation is the San Andreas Fault Zone. The Neenach Volcano was situated directly over the primary San Andreas fault, causing it to be split in two once the transform fault movement began. The average relative motion along the fault is about 1.5 cm per year, equivalent to six inches per decade. Over the course of this movement, the two halves of the volcano drifted about 195 miles (314 kilometers) apart and eroded down into the minor rock formations visible today.

Nootka Fault

The Nootka Fault is an active transform fault running southwest from Nootka Island, near Vancouver Island, British Columbia, Canada.

Queen Charlotte Triple Junction

The Queen Charlotte Triple Junction is a geologic triple junction where three tectonic plates meet: the Pacific Plate, the North American Plate, and the Explorer Plate. The three plate boundaries which intersect here are the Queen Charlotte Fault, the northern Cascadia subduction zone, and the Explorer Ridge. The Queen Charlotte triple junction is currently positioned adjacent to the Queen Charlotte Sound near the Dellwood Knolls off the coast of Vancouver Island. 10 Ma to 1.5 Ma prior to the triple junction's current location, it was located southwest of Vancouver Island The movements of the triple junction have been characterized by two major shifts in the Pacific-North American Tertiary plate tectonic record. First, at approximately 40 Ma the relative plate motions switched from orthogonal convergence to right-lateral strike slip. The variance in location of the triple junction may have also been related to the formation of an independent basin block. This formation could have been produced by fore-arc bending of the Pacific Plate, due to oblique underthrusting prior to 1 Ma which produced stresses sufficient to break the Pacific Plate and isolate the block. Transpression of 15–30 mm/yr since 5 Ma has been taking place, as well as varying amounts of both transpression and transtension occurring before then. To the northwest of the triple junction the Pacific plate currently has 15 degrees of oblique convergence, passing under the North American plate along the Queen Charlotte transform fault zone. The Explorer plate is a small chunk of the Juan de Fuca plate that broke away from the Juan de Fuca Plate about 3.5 Ma and has moved much slower with respect to North America.

Regional Scale Nodes

The National Science Foundation's (NSF) Ocean Observatories Initiative (OOI) Regional Scale Nodes (RSN) component is an electro-optically cabled underwater observatory that directly connects to the global Internet. It is the largest cable-linked seabed observatory in the world, and also the first of its kind in the United States.

Located on the southern part of the Juan de Fuca plate, off the coast of Washington and Oregon, it is the first ocean observatory to span a tectonic plate.

RSN utilizes several high-power, high-bandwidth sub-sea terminals called primary nodes which are linked together by fiber-optic cable and provide support to oceanographic sensors at key locations.

Upon completion of the network in 2014, RSN will cover a distance of over 900 kilometers at depths of up to 3000 meters. Implementation of the OOI Regional Scale Nodes is led by the University of Washington's (UW) School of Oceanography, the UW Applied Physics Laboratory, and L-3 MariPro.

Live RSN data from >100 seafloor and water column instruments will be made available live on the Internet. This will allow both scientists and the general public to study long-term changes in ocean systems over the next 25 years.

Construction of RSN will be completed in 2014. Efforts are substantially aided by the crews of ROPOS (Remotely Operated Platform for Observation Sciences. The 83-day VISIONS ’14 expedition aboard the 274-foot global-class R/V Thomas G. Thompson is responsible for the observatory's final implementation.

Round Mountain (volcano)

Round Mountain is an eroded volcanic outcrop in the Garibaldi Volcanic Belt in British Columbia, Canada, located 8 km southwest of Eanastick Meadows, 9 km (6 mi) east of Brackendale and 10 km (6 mi) south of Mount Garibaldi. It is the highpoint of Paul Ridge and is located in the southwest corner of Garibaldi Provincial Park. Round Mountain formed as a result of subduction of the Juan de Fuca Plate beneath the North American Plate, known as the Cascadia subduction zone. Round Mountain last erupted during the Pleistocene.

Vancouver Whitecaps FC U-23

Vancouver Whitecaps FC U-23, formerly known as Whitecaps FC Reserves, was a Canadian soccer team based in Vancouver, British Columbia, Canada. Although founded in 2005 as part of the development system for the Vancouver Whitecaps USL First Division franchise, beginning in 2011 they became part of the development system for Major League Soccer's Vancouver Whitecaps FC. The team played in the Premier Development League (PDL), the fourth tier of the American Soccer Pyramid, in the Northwest Division of the Western Conference.

The team played its home games at Thunderbird Stadium. The team's colours were blue and white.

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