Editing Plate tectonics (section)

{{Short description|Movement of Earth's lithosphere}}
{{Redirect-distinguish|Tectonic plates|Tectonic Plates (film){{!}}''Tectonic Plates'' (film)}}
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[[File:Tectonic plates 2022.svg|upright=1.35|thumb|Map of Earth's 16 principal tectonic plates<br />
Divergent:
{{legend-line|#a50f15 solid 2px|Spreading center}}
{{legend-line|#e7298a solid 2px|Extension zone}}
Convergent:
{{legend-line|#08519c solid 2px|Subduction zone}}
{{legend-line|#8c6bb1 solid 2px|Collision zone}}
Transform:
{{legend-line|#fe9929 solid 2px|Dextral transform}}
{{legend-line|#006837 solid 2px|Sinistral transform}}]]
{{Geology sidebar}}
{{Geophysics}}

'''Plate tectonics''' ({{etymology|lat|{{Wikt-lang|la|tectonicus}}|}}, {{etymology|grc|''{{Wikt-lang|grc|τεκτονικός}}'' ({{grc-transl|τεκτονικός}})|pertaining to building}}){{sfn|Little|Fowler|Coulson|1990}} is the [[scientific theory]] that the [[Earth]]'s [[lithosphere]] comprises a number of large '''tectonic plates''', which have been slowly moving since 3–4 billion years ago.<ref name="Dhuime2012">{{Cite journal |last1=Dhuime |first1=B |last2=Hawkesworth |first2=CJ |last3=Cawood |first3=PA |last4=Storey |first4=CD |year=2012 |title=A change in the geodynamics of continental growth 3 billion years ago |journal=Science |volume=335 |issue=6074 |pages=1334–1336 |bibcode=2012Sci...335.1334D |doi=10.1126/science.1216066 |pmid=22422979 |s2cid=206538532}}</ref><ref name="Harrison2009">{{Cite journal |last=Harrison |first=TM |year=2009 |title=The Hadean crust: evidence from> 4 Ga zircons |journal=Annual Review of Earth and Planetary Sciences |volume=37 |issue=1 |pages=479–505 |bibcode=2009AREPS..37..479H |doi=10.1146/annurev.earth.031208.100151}}</ref><ref name="Windley2021">{{Cite journal |last1=Windley |first1=BF |last2=Kusky |first2=T |last3=Polat |first3=A |year=2021 |title=Onset of plate tectonics by the Eoarchean |journal=Precambrian Research |volume=352 |page=105980 |bibcode=2021PreR..35205980W |doi=10.1016/j.precamres.2020.105980 |s2cid=228993361}}</ref> The model builds on the concept of {{em|[[continental drift]]}}, an idea developed during the first decades of the 20th century. Plate tectonics came to be accepted by [[Earth science|geoscientists]] after [[seafloor spreading]] was validated in the mid-to-late 1960s. The processes that result in plates and shape [[Earth's crust]] are called ''[[tectonics]]''.
Tectonic plates also occur in other planets and moons.

Earth's lithosphere, the rigid outer shell of the planet including the [[crust (geology)|crust]] and [[upper mantle]], is fractured into seven or eight major plates (depending on how they are defined) and many minor plates or "platelets". Where the plates meet, their relative motion determines the type of '''plate boundary''' (or [[fault (geology)|fault]]): {{em|[[convergent boundary|convergent]]}}, {{em|[[divergent boundary|divergent]]}}, or {{em|[[transform fault|transform]]}}. The relative movement of the plates typically ranges from zero to 10&nbsp;cm annually.{{sfn|Read|Watson|1975}} Faults tend to be geologically active, experiencing [[earthquake]]s, [[volcano|volcanic activity]], [[mountain-building]], and [[oceanic trench]] formation.

Tectonic plates are composed of the oceanic lithosphere and the thicker continental lithosphere, each topped by its own kind of crust. Along [[convergent boundary|convergent plate boundaries]], the process of [[subduction]] carries the edge of one plate down under the other plate and into the [[mantle (geology)|mantle]]. This process reduces the total surface area (crust) of the Earth. The lost surface is balanced by the formation of new [[oceanic crust]] along divergent margins by seafloor spreading, keeping the total [[geoid|surface area]] constant in a tectonic "conveyor belt".

Tectonic plates are relatively [[mechanical properties|rigid]] and float across the ductile [[asthenosphere]] beneath. Lateral density variations in the mantle result in [[mantle convection|convection]] currents, the slow creeping motion of Earth's solid mantle. At a seafloor [[spreading ridge]], plates move away from the ridge, which is a [[topography|topographic]] high, and the newly formed crust cools as it moves away, increasing its [[density]] and contributing to the motion. At a [[subduction]] zone, the relatively cold, dense oceanic crust sinks down into the mantle, forming the downward convecting limb of a [[Mantle convection|mantle cell]],<ref>{{Cite journal |last=Stern |first=Robert J. |year=2002 |title=Subduction zones |journal=[[Reviews of Geophysics]] |volume=40 |issue=4 |pages=1012 |bibcode=2002RvGeo..40.1012S |doi=10.1029/2001RG000108 |s2cid=247695067 |doi-access=free}}</ref> which is the strongest driver of plate motion.<ref>{{Cite journal |last1=Forsyth |first1=D. |last2=Uyeda |first2=S. |year=1975 |title=On the Relative Importance of the Driving Forces of Plate Motion |journal=Geophysical Journal International |volume=43 |issue=1 |pages=163–200 |bibcode=1975GeoJ...43..163F |doi=10.1111/j.1365-246x.1975.tb00631.x |doi-access=free}}</ref>{{sfn|Conrad|Lithgow-Bertelloni|2002}} The relative importance and interaction of other proposed factors such as active convection, upwelling inside the mantle, and tidal drag of the Moon is still the subject of debate.

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