The Pacific Plate is an oceanic
tectonic plate that lies beneath the Pacific Ocean. At , it is the largest tectonic plate.
The plate first came into existence 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 the Farallon Plate to a few remnants along the west coast of North America 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
Hotspot, Hot Spot or Hot spot may refer to:
Places
* Hot Spot, Kentucky, a community in the United States
Arts, entertainment, and media Fictional entities
* Hot Spot (comics), a name for the DC Comics character Isaiah Crockett
* Hot Spot (Tra ...
forming the
Hawaiian Islands
The Hawaiian Islands ( haw, Nā Mokupuni o Hawai‘i) are an archipelago of eight major islands, several atolls, and numerous smaller islets in the North Pacific Ocean, extending some from the island of Hawaii in the south to northernmost ...
.
Boundaries
The north-eastern side is a
divergent boundary with the
Explorer Plate, the
Juan de Fuca Plate and the
Gorda Plate forming respectively the
Explorer Ridge
The Explorer Ridge is a mid-ocean ridge, a divergent tectonic plate boundary located about west of Vancouver Island, British Columbia, Canada. It lies at the northern extremity of the Pacific spreading axis. To its east is the Explorer P ...
, 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
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 (horizontal) ...
, and a boundary with the
Cocos Plate. The south-eastern side is a
divergent boundary with the
Nazca Plate
The Nazca Plate or Nasca Plate, named after the Nazca region of southern Peru, is an oceanic tectonic plate in the eastern Pacific Ocean basin off the west coast of South America. The ongoing subduction, along the Peru–Chile Trench, of the ...
forming the
East Pacific Rise
The East Pacific Rise is a mid-ocean rise (termed an oceanic rise and not a mid-ocean ridge due to its higher rate of spreading that results in less elevation increase and more regular terrain), a divergent tectonic plate boundary located alon ...
.
The southern side is a
divergent boundary with the
Antarctic Plate forming the
Pacific–Antarctic Ridge.
The western side is bounded by the
Okhotsk Plate at the
Kuril–Kamchatka Trench and the
Japan Trench. The plate forms a
convergent boundary
A convergent boundary (also known as a destructive boundary) is an area on Earth where two or more lithospheric plates collide. One plate eventually slides beneath the other, a process known as subduction. The subduction zone can be defined by a ...
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, 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
Zealandia (pronounced ), also known as ( Māori) or Tasmantis, is an almost entirely submerged mass of continental crust that subsided after breaking away from Gondwanaland 83–79 million years ago.Gurnis, M., Hall, C.E., and Lavier, L.L ...
, which 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
A convergent boundary (also known as a destructive boundary) is an area on Earth where two or more lithospheric plates collide. One plate eventually slides beneath the other, a process known as subduction. The subduction zone can be defined by a ...
subducting under the
North American Plate forming the
Aleutian Trench and the corresponding
Aleutian Islands
The Aleutian Islands ( ; ; ale, Unangam Tanangin, "land of the Aleuts"; possibly from the Chukchi ''aliat'', or "island")—also called the Aleut Islands, Aleutic Islands, or, before 1867, the Catherine Archipelago—are a chain of 14 main, ...
.
Paleo-geology of the Pacific Plate
The Pacific Plate is almost entirely
oceanic crust
Oceanic crust is the uppermost layer of the oceanic portion of the tectonic plates. It is composed of the upper oceanic crust, with pillow lavas and a dike complex, and the lower oceanic crust, composed of troctolite, gabbro and ultramafi ...
, but it contains some
continental crust in New Zealand,
Baja California
Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...
, and coastal
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 ...
.
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 trench
Oceanic trenches are prominent long, narrow topographic depressions of the ocean floor. They are typically wide and below the level of the surrounding oceanic floor, but can be thousands of kilometers in length. There are about of oceanic tren ...
es. A
geologic map
A geologic map or geological map is a special-purpose map made to show various geological features. Rock units or geologic strata are shown by color or symbols. Bedding planes and structural features such as faults, folds, are shown with str ...
of the Pacific Ocean seabed shows not only the geologic sequences, and associated
Ring of Fire zones on 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
Plate tectonics (from the la, label= Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large t ...
cycle is early-
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...
(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 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 the west coast of North America (such as the
Juan de Fuca Plate) and the Phoenix Plate to a small remnant near the
Drake Passage,
and destroyed the Izanagi Plate by subduction under Asia.
References
External links
Age of the Ocean Floor
{{Tectonic plates
Tectonic plates
Geology of the Pacific Ocean
Natural history of North America
Natural history of Hawaii
Natural history of Oceania
Natural history of Japan
Geology of the Russian Far East
Geology of California
Geology of New Zealand