Juan de Fuca Plate
Encyclopedia
Juan de Fuca
Ioánnis Fokás , better known by the Spanish transcription of his name, Juan de Fuca , was a Greek-born maritime pilot in the service of the king of Spain, Philip II...
, is a tectonic plate, generated from the Juan de Fuca Ridge
Juan de Fuca Ridge
The Juan de Fuca Ridge is a tectonic spreading center located off the coasts of the state of Washington in the United States and the province of British Columbia in Canada. It runs northward from a transform boundary, the Blanco Fracture Zone, to a triple junction with the Nootka Fault and the...
, and subducting
Subduction
In geology, subduction is the process that takes place at convergent boundaries by which one tectonic plate moves under another tectonic plate, sinking into the Earth's mantle, as the plates converge. These 3D regions of mantle downwellings are known as "Subduction Zones"...
under the northerly portion of the western side of the North American Plate
North American Plate
The North American Plate is a tectonic plate covering most of North America, Greenland, Cuba, Bahamas, and parts of Siberia, Japan and Iceland. It extends eastward to the Mid-Atlantic Ridge and westward to the Chersky Range in eastern Siberia. The plate includes both continental and oceanic crust...
at the Cascadia subduction zone
Cascadia subduction zone
The Cascadia subduction zone is a subduction zone, a type of convergent plate boundary that stretches from northern Vancouver Island to northern California. It is a very long sloping fault that separates the Juan de Fuca and North America plates.New ocean floor is being created offshore of...
. It is bounded on the south by the Blanco Fracture Zone
Blanco Fracture Zone
The Blanco Fracture Zone or Blanco Fault Zone is a transform fault zone running northeast off the coast of Oregon in the Pacific Northwest of the United States which runs between the Gorda Ridge to the south and the Juan de Fuca Ridge to the north...
(running northeast off the coast of Oregon
Oregon
Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...
, USA), on the north by the Nootka Fault
Nootka Fault
The Nootka Fault is an active transform fault running southwest from Nootka Island, near Vancouver Island, British Columbia, Canada.-Geology:...
(running southwest off Nootka Island
Nootka Island
Nootka Island is an island near Vancouver Island in British Columbia, Canada. It contains 534 km² of area. It is separated from Vancouver Island by Nootka Sound and its side-inlets....
, near Vancouver Island
Vancouver Island
Vancouver Island is a large island in British Columbia, Canada. It is one of several North American locations named after George Vancouver, the British Royal Navy officer who explored the Pacific Northwest coast of North America between 1791 and 1794...
, British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
), and along the west by the Pacific Plate
Pacific Plate
The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At 103 million square kilometres, it is the largest tectonic plate....
(which covers most of the Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
and is the largest of Earth's tectonic plates).
The smallest of Earth's tectonic plates, the Juan de Fuca Plate is a remnant part of the once-vast Farallon Plate
Farallon Plate
The Farallon Plate was an ancient oceanic plate, which began subducting under the west coast of the North American Plate— then located in modern Utah— as Pangaea broke apart during the Jurassic Period...
, which is now largely subducted under the North American Plate. 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. When the three fragments are so distinguished, the piece to the south is known as the Gorda Plate
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 as simply the southernmost portion of the neighboring Juan de Fuca Plate, another Farallon remnant.Unlike most tectonic...
and the piece to the north is known as the Explorer Plate
Explorer Plate
The Explorer Plate is an oceanic tectonic plate beneath the Pacific Ocean off the west coast of Vancouver Island, Canada.The eastern boundary of the Explorer Plate is being slowly subducted under the North American Plate, to which it may eventually accrete owing to the slow rate of subduction...
. The separate pieces are demarcated by the large offsets of the undersea spreading zone.
This subducting plate system has formed the Cascade Range
Cascade Range
The Cascade Range 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, and the notable volcanoes known as the High Cascades...
, the Cascade Volcanic Arc
Cascade Volcanoes
The Cascade Volcanoes are a number of volcanoes in a volcanic arc in western North America, extending from southwestern British Columbia through Washington and Oregon to Northern California, a distance of well over 700 mi ...
, and the Pacific Ranges
Pacific Ranges
The Pacific Ranges are the southernmost subdivision of the Coast Mountains portion of the Pacific Cordillera. Located entirely within British Columbia, Canada, they run northwest from the lower stretches of the Fraser River to Bella Coola, north of which are the Kitimat Ranges.The Pacific Ranges...
, along the west coast of North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
from southern British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
to northern California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
. These in turn are part of the Pacific Ring of Fire
Pacific Ring of Fire
The Pacific Ring of Fire is an area where large numbers of earthquakes and volcanic eruptions occur in the basin of the Pacific Ocean. In a horseshoe shape, it is associated with a nearly continuous series of oceanic trenches, volcanic arcs, and volcanic belts and/or plate movements...
, a much larger-scale volcanic feature that extends around much of the rim of the Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
.
Earthquakes
The last megathrust earthquakeMegathrust earthquake
Megathrust earthquakes occur at subduction zones at destructive plate boundaries , where one tectonic plate is forced under another. Due to the shallow dip of the plate boundary, which causes large sections to get stuck, these earthquakes are among the world's largest, with moment magnitudes ...
at the Cascadia subduction zone was the 1700 Cascadia earthquake, estimated to have a moment magnitude
Moment magnitude scale
The moment magnitude scale is used by seismologists to measure the size of earthquakes in terms of the energy released. The magnitude is based on the seismic moment of the earthquake, which is equal to the rigidity of the Earth multiplied by the average amount of slip on the fault and the size of...
of 8.7 to 9.2. Based on carbon dating of local tsunami deposit
Tsunami deposit
A tsunami deposit is a sedimentary unit deposited as the result of of a tsunami. Such deposits may be left onshore during the inundation phase or offshore during the 'backwash' phase. Such deposits are being used to identify past tsunami events and thereby better constrain estimates of both...
s, it occurred around 1700. As reported in National Geographic on 8 December 2003, Japanese
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
records indicate the quake caused a tsunami
Tsunami
A tsunami is a series of water waves caused by the displacement of a large volume of a body of water, typically an ocean or a large lake...
in Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
which occurred during the evening of Tuesday, 26 January 1700.
In 2008, small earthquake
Earthquake
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...
s were observed within the plate. The unusual quakes were described as "more than 600 quakes over the past 10 days in a basin 150 miles southwest of Newport
Newport, Oregon
Newport is a city in Lincoln County, Oregon, United States. It was incorporated in 1882, though the name dates back to the establishment of a post office in 1868...
". 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 heard on hydrophone
Hydrophone
A hydrophone is a microphone designed to be used underwater for recording or listening to underwater sound. Most hydrophones are based on a piezoelectric transducer that generates electricity when subjected to a pressure change...
s, and scientists described the sounds as similar to thunder, and unlike anything heard previously.