The Pacific plate and other principal plates of Earth'slithosphere
ThePacific plate is an oceanictectonic plate that lies beneath thePacific Ocean. At 103 million km2 (40 million sq mi), it is the largest tectonic plate.[2]
The plate first came into existence as a microplate 190 million years ago, at the triple junction between theFarallon,Phoenix, andIzanagi 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 the Americas and the Phoenix plate to a small remnant near theDrake Passage, and destroyed the Izanagi plate by subduction under Asia.
In the south-west, the Pacific plate has a complex but generally convergent boundary with theIndo-Australian plate, subducting under it north of New Zealand forming theTonga Trench and theKermadec Trench. TheAlpine Fault marks atransform boundary between the two plates, and further south the Indo-Australian plate subducts under the Pacific plate forming thePuysegur Trench. The southern part ofZealandia, which is to the east of this boundary, is the plate's largest block of continental crust.[citation needed] Hillis and Müller are reported to consider theBird's Head plate to be moving in unison with the Pacific plate,[4] but Bird considers them to be unconnected.[5]
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 Asianoceanic trenches. Ageological map of the Pacific Ocean seabed shows not only the geologic sequences, and associatedRing 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 theplate tectonics cycle is early-Cretaceous (145 to 137 million years ago).[6]
The Pacific plate originated at thetriple junction of the three main oceanic plates ofPanthalassa, theFarallon,Phoenix, andIzanagi plates, around 190 million years ago. The plate formed because the triple junction had converted to an unstable form surrounded on all sides bytransform 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 theMariana Trench.[7] The growth of the Pacific plate reduced the Farallon plate to a few remnants along the west coast of the Americas (such as theJuan de Fuca plate)[8] and the Phoenix plate to a small remnant near theDrake Passage,[9] and destroyed the Izanagi plate by subduction under Asia.[10]
