Earth

=== Tectonic plates ===
{{Main|Plate tectonics}}
[[File:Tectonic plates (empty).svg|alt=Shows the extent and boundaries of tectonic plates, with superimposed outlines of the continents they support|thumb|[[List of tectonic plates|Earth's major plates]], which are:<ref name="brown_wohletz2005" />{{Hlist|{{Legend inline|#fee6aa|[[Pacific Plate]]}}|{{Legend inline|#fb9a7a|[[African Plate]]<ref group="n" name="jaes41_3_379" />}}|{{Legend inline|#ac8d7f|[[North American Plate]]}}|{{Legend inline|#7fa172|[[Eurasian Plate]]}}|{{Legend inline|#8a9dbe|[[Antarctic Plate]]}}|{{Legend inline|#fcb482|[[Indo-Australian Plate]]}}|{{Legend inline|#ad82b0|[[South American Plate]]}}}}]]

Earth's mechanically rigid outer layer of [[Earth's crust]] and [[upper mantle (Earth)|upper mantle]], the [[lithosphere]], is divided into [[list of tectonic plates|tectonic plates]]. These plates are rigid segments that move relative to each other at one of three boundaries types: at [[convergent boundary|convergent boundaries]], two plates come together; at [[divergent boundary|divergent boundaries]], two plates are pulled apart; and at [[transform fault|transform boundaries]], two plates slide past one another laterally. Along these plate boundaries, earthquakes, [[Volcanism|volcanic activity]], [[Orogeny|mountain-building]], and [[oceanic trench]] formation can occur.<ref name="kious_tilling1999" /> The tectonic plates ride on top of the [[asthenosphere]], the solid but less-viscous part of the upper mantle that can flow and move along with the plates.<ref name="seligman2008" />

As the tectonic plates migrate, oceanic crust is [[Subduction|subducted]] under the leading edges of the plates at convergent boundaries. At the same time, the upwelling of mantle material at divergent boundaries creates mid-ocean ridges. The combination of these processes recycles the oceanic crust back into the mantle. Due to this recycling, most of the ocean floor is less than {{val|100|u=Myr}} old. The oldest oceanic crust is located in the Western Pacific and is estimated to be {{val|200|u=Myr}} old.<ref name=duennebier1999 /><ref name=noaa20070307 /> By comparison, the oldest dated continental crust is {{val|4030|u=Myr|fmt=commas}},<ref name=cmp134_3 /> although zircons have been found preserved as clasts within Eoarchean sedimentary rocks that give ages up to {{val|4400|u=Myr|fmt=commas}}, indicating that at least some continental crust existed at that time.<ref name=science310_5756_1947 />

The seven major plates are the [[Pacific Plate|Pacific]], [[North American Plate|North American]], [[Eurasian Plate|Eurasian]], [[African Plate|African]], [[Antarctic Plate|Antarctic]], [[Indo-Australian Plate|Indo-Australian]], and [[South American Plate|South American]]. Other notable plates include the [[Arabian Plate]], the [[Caribbean Plate]], the [[Nazca Plate]] off the west coast of South America and the [[Scotia Plate]] in the southern Atlantic Ocean. The Australian Plate fused with the Indian Plate between {{val|50|and|55|u=Ma}}. The fastest-moving plates are the oceanic plates, with the [[Cocos Plate]] advancing at a rate of {{convert|75|mm/year|in/year|abbr=on}}<ref name=podp2000 /> and the Pacific Plate moving {{convert|52|–|69|mm/year|in/year|abbr=on}}. At the other extreme, the slowest-moving plate is the South American Plate, progressing at a typical rate of {{convert|10.6|mm/year|in/year|abbr=on}}.<ref name="Argus_etal_2011">{{Cite journal |last1=Argus |first1=D.F. |last2=Gordon |first2=R.G. |last3=DeMets |first3=C. |date=2011 |title=Geologically current motion of 56 plates relative to the no-net-rotation reference frame |journal=Geochemistry, Geophysics, Geosystems |volume=12 |issue=11 |pages=n/a |doi=10.1029/2011GC003751 |bibcode=2011GGG....1211001A |doi-access=free}}</ref>