TheNorth American plate is atectonic plate containing most ofNorth America,Cuba,the Bahamas, extreme northeasternAsia, and parts ofIceland and theAzores. With an area of 76 million km2 (29 million sq mi), it is the Earth's second largest tectonic plate, behind thePacific plate (which borders the plate to the west).
On its western edge, theFarallon plate has beensubducting under the North American plate since theJurassic period. The Farallon plate has almost completely subducted beneath the western portion of the North American plate, leaving that part of the North American plate in contact with the Pacific plate as the San Andreas Fault. TheJuan de Fuca,Explorer,Gorda,Rivera,Cocos andNazca plates are remnants of the Farallon plate. The boundary along the Gulf of California is complex. The gulf is underlain by theGulf of California Rift Zone, a series ofrift basins and transform fault segments from the northern end of the East Pacific Rise in the mouth of the gulf to the San Andreas Fault system in the vicinity of theSalton Trough rift/Brawley seismic zone.[4][5] It is generally accepted that a piece of the North American plate was broken off and transported north as the East Pacific Rise propagated northward, creating the Gulf of California. However, it is as yet unclear whether the oceanic crust between the rise and the mainland coast of Mexico is actually a new plate beginning to converge with the North American plate, consistent with the standard model of rift zone spreading centers generally.[citation needed]
Two major islands of theAzores,Flores andCorvo, lie on the eastern edge of the North American plate, just west of theMid-Atlantic Ridge and near theAzores triple junction. The other major islands of the Azores lie on the African or Eurasian plates.[6][7]
A fewhotspots are thought to exist below the North American plate. The most notable hotspots are theYellowstone (Wyoming),Jemez Lineament (New Mexico), andAnahim (British Columbia) hotspots. These are thought to be caused by a narrow stream of hotmantle convecting up from the Earth'score–mantle boundary called amantle plume,[8] although some geologists think thatupper mantle convection is a more likely cause.[9][10] The Yellowstone and Anahim hotspots are thought to have first arrived during theMiocene period and are still geologically active, creating earthquakes and volcanoes. The Yellowstone hotspot is most notable for theYellowstone Caldera and the manycalderas that lie in theSnake River Plain, while the Anahim hotspot is most notable for theAnahim Volcanic Belt in theNazko Cone area.
For the most part, the North American plate moves in roughly a southwest direction away from the Mid-Atlantic Ridge at a rate of about 2.3 centimeters (~1 inch) per year. At the same time, the Pacific plate is moving to the northwest at a speed of between 7 and 11 centimeters (~3-4 inches) per year. The motion of the plate cannot be driven by subduction as no part of the North American plate is being subducted, except for a small section comprising part of thePuerto Rico Trench; thus other mechanisms continue to be investigated. One study in 2007 suggests that a mantle convective current is propelling the plate.[11]
^Machado, Adriane; Azevedo, José M. M.; Alemeida, Delia P.M.; Farid Chemale Jr. (2008)."Geochemistry of Volcanic Rocks from Faial Island (Azores)"(PDF). Lisbon: e-Terra, GEOTIC – Sociedade Geológica de Portugal. pp. 1–14. Archived fromthe original(PDF) on 11 May 2011. Retrieved17 April 2010.
