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34-566: The Blanco Transform Fault Zone is an approximately 350 km long zone that varies in width between 20 and 75 km. The Blanco Fracture Zone starts about 150 km off Cape Blanco , and extends northwest to about 500 km off of Newport . It consists of a series of deep basins interrupted by transform faults. The western part of the fracture zone, from the Cascadia Depression to the Juan de Fuca Ridge, moves at 1.4 cm/a;

68-418: A consequence of plate tectonics . Lithospheric plates on either side of an active transform fault move in opposite directions; here, strike-slip activity occurs. Fracture zones extend past the transform faults, away from the ridge axis; are usually seismically inactive (because both plate segments are moving in the same direction), although they can display evidence of transform fault activity, primarily in

102-540: A much larger-scale volcanic feature that extends around much of the rim of the Pacific Ocean . 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. Evidence of this earthquake is also seen in the ghost forest along

136-562: A total of 350 km to the west. The section of the Mid-Atlantic Ridge between the two fracture zones is seismically active. The flow of major North Atlantic currents is associated with this fracture zone which hosts a diverse deep water ecosystem. The Heirtzler Fracture Zone was approved by the Advisory Committee on Undersea Features in 1993. The Mendocino Fracture Zone extends for over 4,000 km off

170-587: Is 125 km long and 15 km wide. Juan de Fuca plate The Juan de Fuca plate is a small tectonic plate ( microplate ) generated from the Juan de Fuca Ridge that is subducting beneath 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,

204-547: Is also evidence of active seafloor spreading in this zone, indicating that the Cascadia Depression likely became separated from one of the spreading ridges that border the Blanco Transform Fault Zone. The western part of the zone is made up of a series of depressions separated by transform fault ridges. The Surveyor Depression is the shallowest and smallest of these depressions, reaching a maximum depth of 3300 m and only measuring at 5 km across. It

238-624: Is connected through the Parks Plateau fault to the Cascadia Depression. A small sill connects the Surveyor Depression to the East Blanco Depression, a broad basin which is composed of a series of small deeps ranging from 3600 m to 3700m. Small intermediate ridges rise up a few hundred meters to separate these local ravines. A larger sill rises up to 2900 m depth to separate the East Blanco Depression from

272-456: Is consistent with normal faulting , although interference with the Cascadia Depression spreading center changes the motion on some of the faults. Shallow earthquakes consistent with strike-slip faulting occur on the western side of the zone, but their large distribution indicates that multiple faults exist. Generally these faults run along the walls of the bathymetric basins, but near the Juan de Fuca ridge they become distorted, and rotate towards

306-560: Is estimated that 100 years of US carbon emissions (at current rate) could be stored securely, without risk of leakage back into the atmosphere. 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

340-600: The Juan de Fuca Ridge and the Gorda Ridge . The dominating feature of the fracture zone is the 150 km long Blanco Ridge, which is a high-angle, right-lateral strike slip fault with some component of dip-slip faulting . The Charlie-Gibbs Fracture Zone consists of two fracture zones in the North Atlantic that extend for over 2000 km. These fracture zones displace the Mid-Atlantic Ridge

374-771: 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 . 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

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408-630: The Romanche Trench , this fracture zone separates the North Atlantic and South Atlantic oceans. The trench reaches 7,758 m deep, is 300 km long, and has a width of 19 km. The fracture zone offsets the Mid-Atlantic Ridge by more than 640 km. The Sovanco Fracture Zone is a dextral-slip transform fault running between the Juan de Fuca and Explorer Ridge in the North Pacific Ocean . The fracture zone

442-535: The Blanco zone. The swarm began on March 30 when over 600 measurable tremors began occurring north of the zone within the Juan de Fuca plate . On April 23, activity moved to the Blanco fault zone itself, near its junction with the Gorda Ridge . Another series of earthquakes occurred in June 2015. Spread out over a period of a few days, some reached magnitudes of 5.8. In December 2021, a swarm of earthquakes occurred on

476-757: 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. In plate tectonic reconstructions, the Juan de Fuca plate is referred to as the Vancouver plate between the break-up of the Farallon plate c. 55–52 Ma and the activation of the San Andreas Fault c. 30 Ma. The Juan de Fuca plate system has its origins with Panthalassa 's oceanic basin and crust . This oceanic crust has primarily been subducted under

510-424: 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

544-613: 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. Japanese records indicate that a tsunami occurred in Japan on 26 January 1700, which was likely caused by this earthquake. In 2008, small earthquakes were observed within

578-453: The coast of California and separates the Pacific plate and Gorda plate . The bathymetric depths on the north side of the fracture zone are 800 to 1,200 m shallower than to the south, suggesting the seafloor north of the ridge to be younger. Geologic evidence backs this up, as rocks were found to be 23 to 27 million years younger north of the ridge than to the south. Also known as

612-464: The different ages of the crust on opposite sides of the zone. In actual usage, many transform faults aligned with fracture zones are often loosely referred to as "fracture zones" although technically, they are not. They can be associated with other tectonic features and may be subducted or distorted by later tectonic activity. They are usually defined with bathymetric , gravity and magnetic studies. Mid-ocean ridges are divergent plate boundaries. As

646-587: The eastern segment, from the Cascadia Depression to the Gorda Ridge moves at 3.9 cm/a. The whole zone averages a slip rate of 2.0 cm/a. Through it, Cascadia Channel passes. The principal feature of the eastern portion of the zone is the Blanco Ridge, a 150 km right lateral-moving fault that is responsible for the largest earthquakes in the region. The ridge itself varies between 3.5 and 7 km wide, and peaks between 600 and 1000 m above

680-413: 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

714-490: The final major depression, the West Blanco Depression. The West Blanco Depression is shallow in the south, reaching only a depth of 3400 m, but quickly reaches depth near the Juan de Fuca Ridge, dropping down to 4800 m. This basin is at a slightly different angle than the other western depressions, likely due to interference from the Juan de Fuca Ridge. All of these depressions are likely pull-apart basins,

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748-429: 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. The basaltic formations of the Juan de Fuca plate could potentially be suitable for long-term CO 2 sequestration as part of a carbon capture and storage (CCS) system. Injection of CO 2 would lead to the formation of stable carbonates. It

782-473: The northwest portion of the Blanco Fracture Zone, with multiple being stronger than magnitude 5. On June 15, 2022, a swarm of nine earthquakes took place, the maximum magnitude being 5.6. Fracture Zone A fracture zone is a linear feature on the ocean floor—often hundreds, even thousands of kilometers long—resulting from the action of offset mid-ocean ridge axis segments. They are

816-406: The offset in the magnetic striping, one can then determine the rate of past plate motions. In a similar method, one can use the relative ages of the seafloor on either side of a fracture zone to determine the rate of past plate motions. By comparing how offset similarly aged seafloor is, one can determine how quickly the plate has moved. The Blanco Fracture Zone is a fracture zone running between

850-726: 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. 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 ,

884-515: The plate. The deformation may cause the plate to fragment, with the remaining un-subducted small pieces becoming attached to other plates nearby. In 2016, a geophysical study was published on the possible presence of a layer of buoyant material between the Earth's lithosphere and the asthenosphere under the Juan de Fuca plate. The study extends the theory of partial melt in the lithosphere-asthenosphere boundary to subduction zones, specifically in

918-409: The plates on either side of an offset mid-ocean ridge move, a transform fault forms at the offset between the two ridges. Fracture zones and the transform faults that form them are separate but related features. Transform faults are plate boundaries, meaning that on either side of the fault is a different plate. In contrast, outside of the ridge-ridge transform fault, the crust on both sides belongs to

952-439: The result of extensional stresses from the two nearby spreading centers. Most large events in this zone occur on the Blanco Ridge, as the motion on this fault accounts for the majority of the plate movement. Strike slip faulting occurs in this region; motion on the fault is parallel to the motion of the plate. Tectonic activity in the central part of the zone is weaker and deeper than on the Blanco Ridge. Typically this activity

986-437: The ridge axis instead. On January 9, 1994, a large series or swarm of earthquakes occurred in the East Blanco Depression. Acoustic signals recorded during these events indicated that an eruption occurred in this zone. Further investigation revealed an active hydrothermal vent, the first of its kind to be discovered in a transform fault zone. In March and April 2008, a swarm of moderate earthquakes occurred both near and within

1020-408: The same plate, and there is no relative motion along the junction. The fracture zone is thus the junction between oceanic crustal regions of different ages. Because younger crust is generally higher due to increased thermal buoyancy , the fracture zone is characterized by an offset in elevation with an intervening canyon that may be topographically distinct for hundreds or thousands of kilometers on

1054-486: The sea floor. As many areas of the ocean floor, particularly the Atlantic Ocean, are currently inactive, it can be difficult to find past plate motion. However, by observing the fracture zones, one can determine both the direction and rate of past plate motion. This is found by observing the patterns of magnetic striping on the ocean floor (a result of the reversals of Earth's magnetic field over time). By measuring

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1088-531: The seafloor. The ridge likely formed through extensive shearing and subsequent serpentinization from the intrusion of seawater. The Gorda Depression, a 10 km wide extensional basin , connects the eastern end of the Blanco Ridge to the Gorda Ridge. This basin is around 4400 m deep in the center, 11 km across in the NE-SW direction, and 18 km wide in the NW-SE direction. The Cascadia Depression connects

1122-512: The two halves of the Blanco Transform Fault Zone. The depression is elongated, around 20 km in the NE-SW direction, but only about 8 km in the NW-SE direction. Roughly 500 m of sediments line the floor of the depression, mostly turbidites . Channels cut through the southern end of the depression are remnants of turbidity flows originating from the Missoula floods , but there are also signs of more recent, local turbidity currents . There

1156-453: 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

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