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13-763: The Pacific plate is a major section of the Earth's crust, gradually expanding by the eruption of magma along the East Pacific Rise to the southeast. It is also being subducted far to the northwest into the Aleutian Trench under the North American plate well north of San Francisco. In California, the plate borders the North American plate along a transform boundary, the San Andreas Fault. The westward component of

26-552: Is almost entirely oceanic crust , but it contains some continental crust in New Zealand, Baja California , and coastal California . The Pacific plate has the distinction of showing one of the largest areal sections of the oldest members of seabed geology being entrenched into eastern Asian oceanic trenches . A geologic map of the Pacific Ocean seabed shows not only the geologic sequences, and associated Ring of Fire zones on

39-534: Is an oceanic tectonic plate that lies beneath the Pacific Ocean . At 103 million km (40 million sq mi), it is the largest tectonic plate. The plate first came into existence as a microplate 190 million years ago, at the triple junction between the Farallon , Phoenix , and Izanagi plates . The Pacific plate subsequently grew to where it underlies most of the Pacific Ocean basin. This reduced

52-454: Is approximately 25 km long, and dips at an angle of 38 degrees to the northeast. The Mount Diablo Thrust Fault is capable of generating an earthquake of magnitude M W =6.7. The predicted rupture surface begins 8 km below the surface, and there is thus no surface expression of the fault, and a low likelihood of surface rupture in the event of a large earthquake on the fault. No large historic earthquakes are known to have occurred on

65-550: Is to the east of this boundary, is the plate's largest block of continental crust. Hillis and Müller are reported to consider the Bird's Head plate to be moving in unison with the Pacific plate, but Bird considers them to be unconnected. The northern side is a convergent boundary subducting under the North American plate forming the Aleutian Trench and the corresponding Aleutian Islands (see also: Aleutian Arc ). The Pacific plate

78-778: The Explorer Ridge , the Juan de Fuca Ridge and the Gorda Ridge . In the middle of the eastern side is a transform boundary with the North American plate along the San Andreas Fault , and a boundary with the Cocos plate . The south-eastern side is a divergent boundary with the Nazca plate forming the East Pacific Rise . The southern side is a divergent boundary with the Antarctic plate forming

91-853: The Pacific–Antarctic Ridge . The western side is bounded by the Okhotsk microplate at the Kuril–Kamchatka Trench and the Japan Trench . The plate forms a convergent boundary by subducting under the Philippine Sea plate creating the Mariana Trench , has a transform boundary with the Caroline plate , and has a collision boundary with the North Bismarck plate . In the south-west,

104-841: The Farallon plate to a few remnants along the west coast of the Americas and the Phoenix plate to a small remnant near the Drake Passage , and destroyed the Izanagi plate by subduction under Asia. The Pacific plate contains an interior hot spot forming the Hawaiian Islands . The north-eastern side is a divergent boundary with the Explorer plate , the Juan de Fuca plate and the Gorda plate forming respectively

117-888: The Mount Diablo Thrust Fault. The recurrence interval for large earthquakes along the fault is predicted to be about 400 years. Compressive stresses are produced by offset and converging slip-strike motions between the Calaveras Fault and the Clayton-Marsh Creek-Greenville Fault which manifest in the Mount Diablo Thrust Fault. The Mount Diablo Thrust Fault underlays several cities and unincorporated communities in Contra Costa County: Alamo , Antioch , Blackhawk , Brentwood , Clayton , Concord , Danville , Diablo , San Ramon , and Walnut Creek . Pacific plate The Pacific plate

130-653: The North American plate's motion and the irregularity of the San Andreas Fault results in some compressive force along the San Andreas and its associated faults, thus helping lift the Coast Ranges. The Mount Diablo Thrust Fault and the Great Valley Blind Thrust faults are consequences of this compression. Movement along the Mount Diablo Thrust Fault includes crustal shortening of about 2.6 mm and uplift of about 1 mm per year. The Mount Diablo Thrust Fault

143-697: The Pacific plate has a complex but generally convergent boundary with the Indo-Australian plate , subducting under it north of New Zealand forming the Tonga Trench and the Kermadec Trench . The Alpine Fault marks a transform boundary between the two plates, and further south the Indo-Australian plate subducts under the Pacific plate forming the Puysegur Trench . The southern part of Zealandia , which

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156-544: The ocean's perimeters, but the various ages of the seafloor in a stairstep fashion, youngest to oldest, the oldest being consumed into the Asian oceanic trenches. The oldest part disappearing by way of the plate tectonics cycle is early- Cretaceous (145 to 137 million years ago). The Pacific plate originated at the triple junction of the three main oceanic plates of Panthalassa , the Farallon , Phoenix , and Izanagi plates , around 190 million years ago. The plate formed because

169-411: The triple junction had converted to an unstable form surrounded on all sides by transform faults , due to the development of a kink in one of the plate boundaries. The "Pacific Triangle", the oldest part of the Pacific plate, created during the initial stages of plate formation, is located just east of the Mariana Trench . The growth of the Pacific plate reduced the Farallon plate to a few remnants along

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