Everything about The North American Plate totally explained
The
North American Plate is a
tectonic plate covering most of
North America,
Greenland and part of
Siberia. 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. The interior of the main continental landmass includes an extensive
granitic core called a
craton. Along most of the edges of this craton are fragments of crustal material called
terranes, accreted to the craton by tectonic actions over the long span of geologic time. It is believed that much of North America west of the
Rockies is composed of such terranes.
The easterly side of the North American Plate is a
divergent boundary with the
Eurasian Plate to the north and the
African Plate to the south forming the northern part of the
Mid-Atlantic Ridge. The southerly boundary with the
Cocos Plate to the west and the
Caribbean Plate to the east is a transform fault, represented by the
Cayman Trench under the
Caribbean Sea and the
Motagua Fault through
Guatemala. The rest of the southerly margin which extends east to the Mid Atlantic Ridge and marks the boundary between the North American Plate and the South American Plate remains poorly understood and undefined. The westerly boundary is the
Queen Charlotte Fault running offshore along the coast of Alaska and the
Cascadia subduction zone to the north, the
San Andreas Fault through
California, the
East Pacific Rise in the
Gulf of California, and the
Middle America Trench to the south. On the northerly boundary is a continuation of the Mid-Atlantic ridge called the
Gakkel Ridge. The rest of the boundary in the far northwestern part of the plate extends into
Siberia. This boundary continues from the end of the Gakkel Ridge as the
Laptev Sea Rift, on to a transitional deformation zone in the
Chersky Range, then the
Ulakhan Fault, and finally the
Aleutian Trench to the end of the
Queen Charlotte Fault system.
On its western edge the
Farallon Plate has been
subducting under the North American Plate since the
Jurassic 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. The Juan de Fuca, Cocos, and Nazca Plates are remnants of the Farallon Plate.
The boundary along the
Gulf of California hasn't yet been clearly described and research is ongoing. The Gulf is underlain by the northern end of the
East Pacific Rise. West of the Rise is the Pacific Plate. East of the Rise, most tectonic maps show the North American Plate. 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. The block which broke off is known geologically as the
Salinian Block. However, it's as yet unclear whether the oceanic crust east of the Rise and west of 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.
A few
hotspots are thought to exist below the North American Plate. The most notable hotspots are the
Yellowstone,
Raton and
Anahim hotspots. These are thought to be caused by a narrow stream of
hot mantle convecting up the Earth's
core-mantle boundary called a
mantle plume, although some geologists prefer upper-mantle convection as a cause. The Yellowstone and Anahim hotspots are thought to have first arrived during the
Miocene period and are still geologically active, creating
earthquakes and
volcanoes. The Yellowstone hotspot is most notable for the
Yellowstone Caldera and the many
calderas that lie in the
Snake River Plain while the Anahim hotspot is most notable for the
Anahim Volcanic Belt, currently found in the
Nazko Cone area.
Plate motion
For the most part, the North American Plate moves in roughly a southwest direction away from the Mid-Atlantic Ridge. The motion of the plate can't be driven by subduction as no part of the North American Plate is being subducted (except for a very small section comprising part of the
Puerto Rico Trench), thus other mechanisms continue to be investigated. One recent study suggests that a mantle convective current is propelling the plate.
Further Information
Get more info on 'North American Plate'.
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