Editing Internal structure of Earth (section)

=== Crust and lithosphere ===
{{Main|Earth's crust|Lithosphere}}
[[File:Tectonic plates (empty).svg|alt=Map of Earth's tectonic plates|thumb|upright=1.4|[[List of tectonic plates|Earth's major plates]], which are:{{Hlist|{{Legend inline|#fee6aa|[[Pacific Plate]]}}|{{Legend inline|#fb9a7a|[[African Plate]]}}|{{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 crust ranges from {{convert|5|to(-)|70|km}}<ref>{{cite news |url=https://www.zmescience.com/other/science-abc/layers-earth-structure/ |title=What are the layers of the Earth? |date=21 August 2018 |access-date=28 June 2019 |first=Mihai |last=Andrei |work=ZME Science |archive-date=12 May 2020 |archive-url=https://web.archive.org/web/20200512013554/https://www.zmescience.com/other/science-abc/layers-earth-structure/ |url-status=live }}</ref> in depth and is the outermost layer.<ref>{{cite news |url=https://sciencing.com/earths-structure-crust-inner-core-16911.html |title=Earth's Structure From the Crust to the Inner Core |date=25 April 2017 |access-date=28 June 2019 |first=Lisa |last=Chinn |work=Sciencing |publisher=[[Leaf Group]] Media |archive-date=30 July 2020 |archive-url=https://web.archive.org/web/20200730091442/https://sciencing.com/earths-structure-crust-inner-core-16911.html |url-status=live }}</ref> The thin parts are the [[oceanic crust]], which underlies the ocean basins (5–10&nbsp;km) and is [[mafic]]-rich<ref name="Rogers">{{cite book |url=https://books.google.com/books?id=WA9ST5S_2v0C&pg=PA44 |title=An Introduction to Our Dynamic Planet |date=2008 |publisher=[[Cambridge University Press]] and [[The Open University]] |isbn=978-0-521-49424-3 |editor-last=Rogers |editor-first=N. |page=19 |access-date=2022-08-08 |archive-date=2016-05-02 |archive-url=https://web.archive.org/web/20160502212957/https://books.google.com/books?id=WA9ST5S_2v0C&pg=PA44 |url-status=live }}</ref> (dense iron-magnesium [[silicate mineral]] or [[igneous rock]]).<ref name="Jackson1997">{{cite book |title=Glossary of Geology |date=1997 |publisher=American Geological Institute |isbn=0922152349 |editor1-last=Jackson |editor1-first=Julia A. |edition=4th |location=Alexandria, Virginia |chapter=mafic}}</ref> The thicker crust is the [[continental crust]], which is less dense<ref>{{cite encyclopedia |author=<!--editors. Regardless of what the website gives you as a citation, using "Britannica" as a surname and "The Editors of Encyclopædia" as a forename is really dumb--> |title=Continental crust |encyclopedia=Encyclopædia Britannica |date=5 September 2023 |url=https://www.britannica.com/science/continental-crust |access-date=6 October 2024 }}</ref> and is [[felsic]]-rich (igneous rocks rich in elements that form [[feldspar]] and [[quartz]]).<ref>{{cite book |last1=Schmidt |first1=Victor A. |url=http://geoinfo.amu.edu.pl/wpk/pe/a/harbbook/other/contents.html |title=Planet Earth and the New Geosciences |last2=Harbert |first2=William |year=1998 |isbn=978-0-7872-4296-1 |edition=3rd |page=442 |chapter=The Living Machine: Plate Tectonics |publisher=Kendall/Hunt |access-date=2008-01-28 |archive-url=https://web.archive.org/web/20100124060304/http://geoinfo.amu.edu.pl/wpk/pe/a/harbbook/other/contents.html |archive-date=2010-01-24 |url-status=dead}} {{cite web |title=Unit 3: The Living Machine: Plate Tectonics |website=Planet Earth and the New Geosciences |first1=Victor A. |last1=Schmidt |first2=William |last2=Harbert |publisher=Adam Mickiewicz University |location=Poznańb|url=http://geoinfo.amu.edu.pl/wpk/pe/a/harbbook/c_iii/chap03.html |url-status=dead |archive-url=https://web.archive.org/web/20100328212854/http://geoinfo.amu.edu.pl/wpk/pe/a/harbbook/c_iii/chap03.html |archive-date=2010-03-28}}</ref> The rocks of the crust fall into two major categories – [[sial]] (aluminium silicate) and [[Sima (geology)|sima]] (magnesium silicate).<ref>{{Cite journal |last=Hess |first=H. |date=1955-01-01 |title=The oceanic crust |url=https://elischolar.library.yale.edu/journal_of_marine_research/854 |journal=Journal of Marine Research |volume=14 |issue=4 |pages=424 |quote=It has been common practice to subdivide the crust into sial and sima. These terms refer to generalized compositions, sial being those rocks rich in Si and Al and sima those rich in Si and Mg.}}</ref> It is estimated that sima starts about 11&nbsp;km below the [[Conrad discontinuity]],<ref name="Kearey">{{cite book |last1=Kearey |first1=P. |url=https://books.google.com/books?id=HYqZntfg25UC&dq=%22conrad+discontinuity%22&pg=PA19 |title=Global Tectonics |last2=Klepeis |first2=K. A. |last3=Vine |first3=F. J. |publisher=[[John Wiley & Sons]] |year=2009 |isbn=9781405107778 |edition=3 |pages=19–21 |accessdate=30 June 2012}}</ref> though the discontinuity is not distinct and can be absent in some continental regions.<ref name="Lowrie">{{cite book |last=Lowrie |first=W. |url=https://books.google.com/books?id=7vR2RJSIGVoC&dq=%22conrad+discontinuity%22&pg=PA149 |title=Fundamentals of Geophysics |publisher=[[Cambridge University Press]] |year=1997 |isbn=9780521467285 |pages=149 |accessdate=30 June 2012}}</ref>

Earth's lithosphere consists of the crust and the uppermost [[Earth's mantle|mantle]].<ref>{{Cite book |url= |title=Human Geoscience |publisher=[[Springer Science+Business Media]] |year=2020 |isbn=978-981-329-224-6 |editor-last=Himiyama |editor-first=Yukio |location=Singapore |page=27 |oclc=1121043185 |editor-last2=Satake |editor-first2=Kenji |editor-last3=Oki |editor-first3=Taikan}}</ref> The crust-mantle boundary occurs as two physically different phenomena. The [[Mohorovičić discontinuity]] is a distinct change of [[seismic wave]] velocity. This is caused by a change in the rock's density<ref>{{Citation |last1=Rudnick |first1=R. L. |title=3.01 – Composition of the Continental Crust |date=2003-01-01 |url=http://www.sciencedirect.com/science/article/pii/B0080437516030164 |journal=Treatise on Geochemistry |volume=3 |page=659 |editor-last=Holland |editor-first=Heinrich D. |publisher=Pergamon |bibcode=2003TrGeo...3....1R |doi=10.1016/b0-08-043751-6/03016-4 |isbn=978-0-08-043751-4 |access-date=2019-11-21 |last2=Gao |first2=S. |editor2-last=Turekian |editor2-first=Karl K.|url-access=subscription }}</ref> – immediately above the Moho, the velocities of primary seismic waves ([[P wave]]) are consistent with those through [[basalt]] (6.7–7.2&nbsp;km/s), and below they are similar to those through [[peridotite]] or [[dunite]] (7.6–8.6&nbsp;km/s).<ref name="Badescu">{{cite book |first1=R. B. |last1=Cathcart |url=https://books.google.com/books?id=5bZBEM31K1MC&pg=PA169 |title=Macro-engineering: a challenge for the future |first2=M. M. |last2=Ćirković |date=2006 |publisher=Springer |isbn=978-1-4020-3739-9 |editor1-first=Viorel |editor1-last=Badescu |page=169 |editor2-first=Richard Brook |editor2-last=Cathcart |editor2-link=Richard Cathcart |editor3-first=Roelof D. |editor3-last=Schuiling |name-list-style=amp}}</ref> Second, in oceanic crust, there is a chemical discontinuity between [[ultramafic]] cumulates and tectonized [[Peridotite|harzburgites]], which has been observed from deep parts of the oceanic crust that have been [[obduction|obducted]] onto the continental crust and preserved as [[ophiolites|ophiolite sequences]].{{Clarify|reason=Too technical, a simpler explanation is warranted|date=August 2022}}

Many rocks making up Earth's crust formed less than 100 [[million years]] ago; however, the oldest known mineral grains are about 4.4 [[billion years]] old, indicating that Earth has had a solid crust for at least 4.4 billion years.<ref>{{cite web |url=http://spaceflightnow.com/news/n0101/14earthwater/ |title=Oldest rock shows Earth was a hospitable young planet |agency=National Science Foundation |archive-url=https://web.archive.org/web/20090628164134/http://spaceflightnow.com/news/n0101/14earthwater/ |archive-date=2009-06-28 |website=Spaceflight Now |date=2001-01-14 |access-date=2012-01-27}}</ref>