Earth

== Physical characteristics ==
<!--linked from 'Earth physical characteristics tables'-->
{{Further|Geophysics}}

=== Size and shape ===
{{Main|Figure of the Earth}}
{{Further|Earth radius|Earth's circumference|Spherical Earth{{!}}Earth curvature|Geomorphology}}
{{See also|List of highest mountains on Earth}}
[[File:Earth2014shape SouthAmerica small.jpg|thumb|upright=1.3|Earth's western hemisphere showing topography relative to Earth's center instead of to [[mean sea level]], as in common topographic maps]]
[[Figure of the Earth|Earth has a rounded shape]], through [[hydrostatic equilibrium]],<ref name="Horner 2021">{{cite web | last=Horner | first=Jonti | title=I've always wondered: why are the stars, planets and moons round, when comets and asteroids aren't? | website=The Conversation | date=2021-07-16 | url=https://theconversation.com/amp/ive-always-wondered-why-are-the-stars-planets-and-moons-round-when-comets-and-asteroids-arent-160541 | access-date=2023-03-03}}</ref> with an average diameter of {{convert|12742|km|mi|sp=us}}, making it the [[List of Solar System objects by size|fifth largest]] [[Planet#Planetary-mass object|planetary sized]] and largest [[terrestrial planet|terrestrial object]] of the [[Solar System]].<ref>{{Cite web |last=Lea |first=Robert |date=2021-07-06 |title=How big is Earth? |url=https://www.space.com/17638-how-big-is-earth.html |archive-url=https://web.archive.org/web/20240109225632/https://www.space.com/17638-how-big-is-earth.html |archive-date=2024-01-09 |access-date=2024-01-11 |website=Space.com |language=en}}</ref>

Due to [[Earth's rotation]] it has the shape of an [[Earth ellipsoid|ellipsoid]], [[equatorial bulge|bulging at its Equator]]; its diameter is {{convert|43|km|mi|sp=us}} longer there than at its [[Geographical pole|poles]].<ref name="ngdc2006" /><ref name="milbert_smith96" />
Earth's shape furthermore has local [[topography|topographic]] variations. Though the largest local variations, like the [[Mariana Trench]] ({{convert|10925|m|ft|disp=or|abbr=|sp=us}} below local sea level),<ref>{{Cite journal|last1=Stewart|first1=Heather A.|last2=Jamieson|first2=Alan J.|date=2019|title=The five deeps: The location and depth of the deepest place in each of the world's oceans|journal=Earth-Science Reviews|language=en|volume=197|pages=102896|doi=10.1016/j.earscirev.2019.102896|bibcode=2019ESRv..19702896S|issn=0012-8252|doi-access=free}}</ref> only shortens Earth's average radius by 0.17% and [[Mount Everest]] ({{convert|8848|m|ft|disp=or|sp=us}} above local sea level) lengthens it by only 0.14%.{{refn|group=n| If Earth were shrunk to the size of a [[billiard ball]], some areas of Earth such as large mountain ranges and oceanic trenches would feel like tiny imperfections, whereas much of the planet, including the [[Great Plains]] and the [[abyssal plain]]s, would feel smoother.<ref>{{cite web |url=http://billiards.colostate.edu/bd_articles/2013/june13.pdf |title=Is a Pool Ball Smoother than the Earth? |publisher=Billiards Digest |date=1 June 2013 |access-date=26 November 2014}}</ref>}}<ref>{{cite web|url=https://serc.carleton.edu/quantskills/activities/botec_himalayas.html|title=Back-of-the-Envelope Calculations: Scale of the Himalayas|work=[[Carleton University]]|last1=Tewksbury|first1=Barbara|access-date=19 October 2020}}</ref> Since Earth's surface is farthest out from Earth's [[center of mass]] at its equatorial bulge, the summit of the volcano [[Chimborazo]] in Ecuador ({{Convert|6384.4|km|mi|1|abbr=on|disp=or}}) is its farthest point out.<ref name=ps20_5_16 /><ref>{{cite web |url=https://www.npr.org/templates/story/story.php?storyId=9428163 |title=The 'Highest' Spot on Earth |last1=Krulwich|first1=Robert|author-link=Robert Krulwich|work=NPR |date=7 April 2007 |access-date=31 July 2012}}</ref>
Parallel to the rigid land topography [[Ocean surface topography|the Ocean exhibits a more dynamic topography]].<ref>{{Cite web |title=Ocean Surface Topography |url=https://sealevel.jpl.nasa.gov/ocean-observation/ocean-surface-topography |access-date=16 June 2022 |website=Ocean Surface Topography from Space |publisher = NASA |language=en}}</ref>

To measure the local variation of Earth's topography, [[geodesy]] employs an idealized Earth producing a shape called a [[geoid]]. Such a geoid shape is gained if the ocean is idealized, covering Earth completely and without any perturbations such as tides and winds. The result is a smooth but gravitational irregular geoid surface, providing a mean sea level (MSL) as a reference level for topographic measurements.<ref>{{Cite web|title=What is the geoid?|url=https://oceanservice.noaa.gov/facts/geoid.html|access-date=10 October 2020|publisher=[[National Ocean Service]]|language=EN-US}}</ref>

=== Surface ===
{{Further|Planetary surface|Land cover|Land|Pedosphere|Ocean|Sea|Cryosphere|Peplosphere}}
[[File:Global View of the Arctic and Antarctic.jpg|thumb|A [[compositing|composite]] image of Earth, with its different types of surface discernible: Earth's surface dominating Ocean (blue), Africa with lush (green) to dry (brown) land and Earth's polar ice in the form of [[Antarctic sea ice]] (grey) covering the [[Southern Ocean|Antarctic or Southern Ocean]] and the [[Antarctic ice sheet]] (white) covering [[Antarctica]].]]
[[File:AYool topography 15min.png|thumb|upright=1.3|[[Terrain|Relief]] of [[Earth's crust]]]]
Earth's surface is the boundary between the atmosphere, and the solid Earth and oceans. Defined in this way, it has an area of about {{convert|510|e6km2|e6sqmi|0|abbr=unit}}.<ref name="Pidwirny 2006_8" /> Earth can be divided into two [[Hemispheres of Earth|hemispheres]]: by [[latitude]] into the polar [[Northern Hemisphere|Northern]] and [[Southern Hemisphere|Southern]] hemispheres; or by [[longitude]] into the continental [[Eastern Hemisphere|Eastern]] and [[Western Hemisphere|Western]] hemispheres.

Most of Earth's surface is ocean water: 70.8% or {{convert|361|e6km2|e6sqmi|abbr=unit}}.<ref name="Percentage">{{Cite web|url=http://www.physicalgeography.net/fundamentals/8o.html|title=8(o) Introduction to the Oceans|website=www.physicalgeography.net}}</ref> This vast pool of salty water is often called the ''world ocean'',<ref name="Janin Mandia 2012 p. 20">{{cite book |last1=Janin |first1=H. |last2=Mandia |first2=S.A. |title=Rising Sea Levels: An Introduction to Cause and Impact |publisher=McFarland, Incorporated, Publishers |year=2012 |isbn=978-0-7864-5956-8 |url={{GBurl|id=it27LP5V0ugC|p=20}} |access-date=26 August 2022 |page=20}}</ref><ref name="Ro 2020">{{cite web |last=Ro |first=Christine |title=Is It Ocean Or Oceans? |website=Forbes |date=3 February 2020 |url=https://www.forbes.com/sites/christinero/2020/02/03/is-it-ocean-or-oceans/ |access-date=26 August 2022}}</ref> and makes Earth with its dynamic [[hydrosphere]] a water world<ref name="Smith 2021">{{cite web |last=Smith |first=Yvette |title=Earth Is a Water World |website=NASA |date=7 June 2021 |url=http://www.nasa.gov/image-feature/earth-is-a-water-world |access-date=27 August 2022}}</ref><ref name="National Geographic Society 2022">{{cite web |title=Water-Worlds |website=National Geographic Society |date=20 May 2022 |url=https://education.nationalgeographic.org/resource/water-worlds/ |access-date=24 August 2022}}</ref> or [[ocean world]].<ref name="Lunine 2017 pp. 123–130">{{cite journal |last=Lunine |first=Jonathan I. |title=Ocean worlds exploration |journal=Acta Astronautica |publisher=Elsevier BV |volume=131 |year=2017 |issn=0094-5765 |doi=10.1016/j.actaastro.2016.11.017 |pages=123–130|bibcode=2017AcAau.131..123L |doi-access=free }}</ref><ref name="Ocean Worlds">{{cite web |title=Ocean Worlds |website=Ocean Worlds |url=http://www.nasa.gov/specials/ocean-worlds/index.html |access-date=27 August 2022 |archive-date=27 August 2022 |archive-url=https://web.archive.org/web/20220827003111/https://www.nasa.gov/specials/ocean-worlds/index.html |url-status=dead }}</ref> Indeed, in Earth's early history the ocean may have covered Earth completely.<ref name="Voosen p.">{{cite journal | last=Voosen | first=Paul | title=Ancient Earth was a water world | journal=Science | publisher=American Association for the Advancement of Science (AAAS) | date=9 March 2021 | volume=371 | issue=6534 | pages=1088–1089 | issn=0036-8075 | doi=10.1126/science.abh4289 | pmid=33707245 | s2cid=241687784 }}</ref> The world ocean is commonly divided into the Pacific Ocean, Atlantic Ocean, Indian Ocean, [[Southern Ocean|Antarctic or Southern Ocean]], and Arctic Ocean, from largest to smallest. The ocean covers [[oceanic crust|Earth's oceanic crust]], with the [[shelf sea]]s covering the [[continental shelf|shelves]] of the [[continental crust]] to a lesser extent. The oceanic crust forms large [[oceanic basin]]s with features like [[abyssal plain]]s, [[seamount]]s, [[submarine volcano]]es,<ref name="ngdc2006" /> [[oceanic trench]]es, [[submarine canyon]]s, [[oceanic plateau]]s, and a globe-spanning [[mid-ocean ridge]] system.

At Earth's [[polar regions of Earth|polar regions]], the [[ocean surface]] is covered by seasonally variable amounts of [[sea ice]] that often connects with polar land, [[permafrost]] and [[ice sheet]]s, forming [[polar ice cap]]s.

Earth's land covers 29.2%, or {{convert|149|e6km2|e6sqmi|abbr=unit}} of Earth's surface. The land surface includes many islands around the globe, but most of the land surface is taken by the four continental [[landmass]]es, which are (in descending order): [[Afro-Eurasia|Africa-Eurasia]], [[Americas|America (landmass)]], [[Antarctica]], and [[Mainland Australia|Australia (landmass)]].<ref name="DunnMitchell2016">{{cite book|first1=Ross E.|last1=Dunn|first2=Laura J.|last2=Mitchell|first3=Kerry|last3=Ward|title=The New World History: A Field Guide for Teachers and Researchers|url={{GBurl|id=-aowDwAAQBAJ|p=232}}|year=2016|publisher=Univ of California Press|isbn=978-0-520-28989-5|pages=232–}}</ref><ref name="Dempsey 2013">{{cite web |last=Dempsey |first=Caitlin |title=Geography Facts about the World's Continents |website=Geography Realm |date=15 October 2013 |url=https://www.geographyrealm.com/continents/ |access-date=26 August 2022}}</ref><ref name="McColl">{{cite encyclopedia|title=continents|encyclopedia=Encyclopedia of World Geography|volume=1|url={{GBurl|id=DJgnebGbAB8C|p=215}}|editor=R.W. McColl|year=2005|publisher=Facts on File, Inc.|isbn=978-0-8160-7229-3|page=215|access-date=25 August 2022|quote=And since Africa and Asia are connected at the Suez Peninsula, Europe, Africa, and Asia are sometimes combined as Afro-Eurasia or Eurafrasia. The International Olympic Committee's official flag, containing [...] the single continent of America (North and South America being connected as the Isthmus of Panama).}}</ref> These landmasses are further broken down and grouped into the [[continent]]s. The [[terrain]] of the land surface varies greatly and consists of mountains, [[desert]]s, [[plain]]s, [[plateau]]s, and other [[landform]]s. The elevation of the land surface varies from a low point of {{convert|-418|m|ft|abbr=on}} at the [[Dead Sea]], to a maximum altitude of {{convert|8,848|m|ft|abbr=on}} at the top of [[Mount Everest]]. The mean height of land above sea level is about {{convert|797|m|ft|abbr=on}}.<ref>{{cite web|last=Center|first=National Geophysical Data|title=Hypsographic Curve of Earth's Surface from ETOPO1|url=https://ngdc.noaa.gov/mgg/global/etopo1_surface_histogram.html|website=ngdc.noaa.gov|date=19 August 2020 }}</ref>

Land can be [[land cover|covered]] by [[surface water]], snow, ice, artificial structures or vegetation. Most of Earth's land hosts vegetation,<ref name="Carlowicz Simmon 2019">{{cite web | last1=Carlowicz | first1=Michael | last2=Simmon | first2=Robert | title=Seeing Forests for the Trees and the Carbon: Mapping the World's Forests in Three Dimensions | website=NASA Earth Observatory | date=15 July 2019 | url=https://earthobservatory.nasa.gov/features/ForestCarbon#:~:text=They%20cover%20about%2030%20percent,percent%20of%20the%20Earth's%20land. | access-date=31 December 2022}}</ref> but [[ice sheet]]s (10%,<ref name="National Geographic Society 2006">{{cite web | title=Ice Sheet | website=National Geographic Society | date=2006-08-06 | url=https://education.nationalgeographic.org/resource/ice-sheet/ | access-date=2023-01-03}}</ref> not including the equally large land under [[permafrost]])<ref name="Obu 2021 p.">{{cite journal | last=Obu | first=J. | title=How Much of the Earth's Surface is Underlain by Permafrost? | journal=Journal of Geophysical Research: Earth Surface | publisher=American Geophysical Union (AGU) | volume=126 | issue=5 | year=2021 | issn=2169-9003 | doi=10.1029/2021jf006123 | page=| bibcode=2021JGRF..12606123O | s2cid=235532921 }}</ref> or cold as well as hot [[desert]]s (33%)<ref name="Cain 2010">{{cite web | last=Cain | first=Fraser | title=What Percentage of the Earth's Land Surface is Desert? | website=Universe Today | date=2010-06-01 | url=https://www.universetoday.com/65639/what-percentage-of-the-earths-land-surface-is-desert/ | access-date=2023-01-03}}</ref> occupy also considerable amounts of it.

The [[pedosphere]] is the outermost layer of Earth's land surface and is composed of soil and subject to [[soil formation]] processes. Soil is crucial for land to be arable. Earth's total [[arable land]] is 10.7% of the land surface, with 1.3% being permanent cropland.<ref>{{cite web |title=World Bank arable land |url=http://data.worldbank.org/indicator/AG.LND.ARBL.ZS/countries/1W?display=graph |publisher=World Bank |access-date=19 October 2015}}</ref><ref>{{cite web |title=World Bank permanent cropland |url=http://data.worldbank.org/indicator/AG.LND.CROP.ZS/countries?display=graph |publisher=World Bank |access-date=19 October 2015}}</ref> Earth has an estimated {{convert|16.7|e6km2|e6sqmi|abbr=unit}} of cropland and {{convert|33.5|e6km2|e6sqmi|abbr=unit}} of pastureland.<ref name="Hooke2012">{{cite journal |url=https://www.geosociety.org/gsatoday/archive/22/12/pdf/gt1212.pdf |title=Land transformation by humans: A review |journal=GSA Today |first1=Roger LeB. |last1=Hooke |first2=José F. |last2=Martín-Duque |first3=Javier |last3=Pedraza |volume=22 |issue=12 |pages=4–10 |date=December 2012 |doi=10.1130/GSAT151A.1|bibcode=2012GSAT...12l...4H }}</ref>

The land surface and the [[ocean floor]] form the top of [[Earth's crust]], which together with parts of the [[upper mantle (Earth)|upper mantle]] form [[Lithosphere#Earth's lithosphere|Earth's lithosphere]]. Earth's crust may be divided into [[oceanic crust|oceanic]] and [[continental crust|continental]] crust. Beneath the ocean-floor sediments, the oceanic crust is predominantly [[basalt]]ic, while the continental crust may include lower density materials such as [[granite]], sediments and metamorphic rocks.<ref name="layers_earth" /> Nearly 75% of the continental surfaces are covered by sedimentary rocks, although they form about 5% of the mass of the crust.<ref name=jessey />

Earth's surface [[topography]] comprises both the [[ocean surface topography|topography of the ocean surface]], and the [[hypsometry|shape]] of Earth's land surface. The submarine terrain of the ocean floor has an average [[bathymetric]] depth of 4&nbsp;km, and is as varied as the terrain above sea level. Earth's surface is continually being shaped by internal [[plate tectonic]] processes including [[earthquakes]] and [[volcanism]]; by [[weathering]] and [[erosion]] driven by ice, water, wind and temperature; and by [[biological processes]] including the growth and decomposition of [[biomass]] into [[soil]].<ref name="kring" /><ref>{{cite book|last=Martin|first=Ronald|url={{GBurl|id=agaOKrvAoeAC}}|title=Earth's Evolving Systems: The History of Planet Earth|publisher=Jones & Bartlett Learning|year=2011|isbn=978-0-7637-8001-2|oclc=635476788}}</ref>

=== 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>

=== Internal structure ===
{{Main|Internal structure of Earth}}

{| class="wikitable sortable" style="float: right; clear: right; margin-left: 2em; text-align:center;"
|+Geologic layers of Earth<ref name=pnas76_9_4192>{{cite journal |last1=Jordan |first1=T. H. |title=Structural geology of the Earth's interior |journal=Proceedings of the National Academy of Sciences of the United States of America |year=1979 |volume=76 |issue=9 |pages=4192–4200 |doi=10.1073/pnas.76.9.4192 |pmid=16592703 |pmc=411539 |bibcode=1979PNAS...76.4192J|doi-access=free }}</ref>
| colspan="3" style="font-size:smaller; text-align:center;" |[[File:Earth-cutaway-schematic-english.svg|center|frameless]]Illustration of Earth's cutaway, not to scale
|-
!Depth<span style="font-size: smaller;"><ref name=robertson2001>{{cite web |last1=Robertson |first1=Eugene C. |date=26 July 2001 |url=http://pubs.usgs.gov/gip/interior/ |title=The Interior of the Earth |publisher=USGS |access-date=24 March 2007}}</ref><br />(km)</span>
! Component <br />layer name
!Density<br /><span style="font-size: smaller;">(g/cm<sup>3</sup>)</span>
|-
|0–60
| style="text-align:left;" |[[Earth's lithosphere|Lithosphere]]<ref group="n">Locally varies between {{val|5|and|200|u=km}}.</ref>
|—
|-
|0–35
| style="text-align:left;" |[[Earth's crust|Crust]]<ref group="n">Locally varies between {{val|5|and|70|u=km}}.</ref>
|2.2–2.9
|-
|35–660
| style="text-align:left;" |[[Upper mantle (Earth)|Upper mantle]]
|3.4–4.4
|-
|660–2890
| style="text-align:left;" |[[Lower mantle (Earth)|Lower mantle]]
|3.4–5.6
|-
|100–700
| style="text-align:left;" |[[Asthenosphere]]
|—
|-
|2890–5100
| style="text-align:left;" |[[Earth's outer core|Outer core]]
|9.9–12.2
|-
|5100–6378
| style="text-align:left;" |[[Earth's inner core|Inner core]]
|12.8–13.1
|}

Earth's interior, like that of the other terrestrial planets, is divided into layers by their [[chemical]] or physical ([[Rheology|rheological]]) properties. The outer layer is a chemically distinct [[Silicate minerals|silicate]] solid crust, which is underlain by a highly [[viscous]] solid mantle. The crust is separated from the mantle by the [[Mohorovičić discontinuity]].<ref name="GeolSoc" /> The thickness of the crust varies from about {{convert|6|km|mi|sp=us}} under the oceans to {{convert|30|-|50|km|mi|abbr=on}} for the continents. The crust and the cold, rigid, top of the [[upper mantle]] are collectively known as the lithosphere, which is divided into independently moving tectonic plates.<ref>{{cite news|url=https://education.nationalgeographic.org/resource/lithosphere/|title=Lithosphere|work=[[National Geographic]]|last1=Micalizio|first1=Caryl-Sue|last2=Evers|first2=Jeannie|date=20 May 2015|access-date=13 October 2020}}</ref>

Beneath the lithosphere is the [[asthenosphere]], a relatively low-viscosity layer on which the lithosphere rides. Important changes in crystal structure within the mantle occur at {{convert|410|and|660|km|mi|abbr=on}} below the surface, spanning a [[Transition zone (Earth)|transition zone]] that separates the upper and lower mantle. Beneath the mantle, an extremely low viscosity liquid [[outer core]] lies above a solid [[Earth's inner core|inner core]].<ref name=tanimoto_ahrens1995 /> Earth's inner core may be rotating at a slightly higher [[angular velocity]] than the remainder of the planet, advancing by 0.1–0.5° per year, although both somewhat higher and much lower rates have also been proposed.<ref name="Deuss_2014" /> The radius of the inner core is about one-fifth of that of Earth.
{{anchor|Density}}Density increases with depth, as described in the table on the right.

Among the Solar System's planetary-sized objects Earth is the [[List of solar system objects by size|object with the highest density]].

=== Chemical composition ===
{{See also|Abundance of elements on Earth}}

[[Earth mass|Earth's mass]] is approximately {{val|5.97|e=24|ul=kg}} (5,970 [[yottagram|Yg]]). It is composed mostly of iron (32.1% [[Mass fraction (chemistry)|by mass]]), [[oxygen]] (30.1%), [[silicon]] (15.1%), [[magnesium]] (13.9%), [[sulfur]] (2.9%), [[nickel]] (1.8%), [[calcium]] (1.5%), and [[aluminium]] (1.4%), with the remaining 1.2% consisting of trace amounts of other elements. Due to [[Planetary differentiation#Gravitational separation|gravitational separation]], the core is primarily composed of the denser elements: iron (88.8%), with smaller amounts of nickel (5.8%), sulfur (4.5%), and less than 1% trace elements.<ref name="pnas71_12_6973" /><ref name="comp" /> The most common rock constituents of the crust are [[oxide]]s. Over 99% of the [[Earth's crust|crust]] is composed of various oxides of eleven elements, principally oxides containing silicon (the [[silicate mineral]]s), aluminium, iron, calcium, magnesium, potassium, or sodium.<ref name="brown_mussett1981" /><ref name="pnas71_12_6973" />

=== Internal heat ===
{{Main|Earth's internal heat budget}}
[[File:Earth heat flow.jpg|upright=1.3|thumb|A map of [[heat flow]] from Earth's interior to the surface of Earth's crust, mostly along the [[oceanic ridge]]s]]
The major heat-producing [[isotope]]s within Earth are [[potassium-40]], [[uranium-238]], and [[thorium-232]].<ref name=sanders20031210 /> At the center, the temperature may be up to {{convert|6000|C|F}},<ref>{{cite web |title=The Earth's Centre is 1000 Degrees Hotter than Previously Thought |url=http://www.esrf.eu/news/general/Earth-Center-Hotter |website=The European Synchrotron (ESRF) |access-date=12 April 2015 |archive-url=https://web.archive.org/web/20130628075455/http://www.esrf.eu/news/general/Earth-Center-Hotter/Earth-Centre-Hotter/ |archive-date=28 June 2013 |date=25 April 2013 |url-status=dead }}</ref> and the pressure could reach {{convert|360|GPa|e6psi|abbr=unit|lk=on}}.<ref name=ptrsl360_1795_1227 /> Because much of the heat is provided by radioactive decay, scientists postulate that early in Earth's history, before isotopes with short half-lives were depleted, Earth's heat production was much higher. At approximately {{val|3|ul=Gyr}}, twice the present-day heat would have been produced, increasing the rates of [[mantle convection]] and plate tectonics, and allowing the production of uncommon [[igneous rock]]s such as [[komatiite]]s that are rarely formed today.<ref name="T&S 137" /><ref name=epsl121_1 />

The mean heat loss from Earth is {{val|87|u=mW m<sup>−2</sup>}}, for a global heat loss of {{val|4.42|e=13|u=W}}.<ref name=jg31_3_267 /> A portion of the core's thermal energy is transported toward the crust by [[mantle plume]]s, a form of convection consisting of upwellings of higher-temperature rock. These plumes can produce [[Hotspot (geology)|hotspots]] and [[flood basalt]]s.<ref name=science246_4926_103 /> More of the heat in Earth is lost through plate tectonics, by mantle upwelling associated with [[mid-ocean ridge]]s. The final major mode of heat loss is through conduction through the lithosphere, the majority of which occurs under the oceans because the crust there is much thinner than that of the continents.<ref name="heat loss" />

=== Gravitational field ===
{{Main|Gravity of Earth}}
The [[gravity of Earth]] is the [[acceleration]] that is imparted to objects due to the distribution of mass within Earth. Near Earth's surface, [[gravitational acceleration]] is approximately {{convert|9.8|m/s2|abbr=on}}. Local differences in topography, geology, and deeper tectonic structure cause local and broad regional differences in Earth's gravitational field, known as [[Gravity anomaly|gravity anomalies]].<ref>{{cite journal |first1=A. B. |last1=Watts |first2=S. F. |last2=Daly |title=Long wavelength gravity and topography anomalies |journal=Annual Review of Earth and Planetary Sciences |volume=9 |pages=415–418 |date=May 1981 |issue=1 |doi=10.1146/annurev.ea.09.050181.002215 |bibcode=1981AREPS...9..415W}}</ref>

=== Magnetic field ===
{{Main|Earth's magnetic field}}
[[File:Magnetosphere Levels-en.svg|alt=Diagram showing the magnetic field lines of Earth's magnetosphere. The lines are swept back in the anti-solar direction under the influence of the solar wind.|thumb|A schematic view of Earth's magnetosphere with [[solar wind]] flowing from left to right]]
The main part of Earth's magnetic field is generated in the core, the site of a [[Dynamo theory|dynamo]] process that converts the kinetic energy of thermally and compositionally driven convection into electrical and magnetic field energy. The field extends outwards from the core, through the mantle, and up to Earth's surface, where it is, approximately, a [[dipole]]. The poles of the dipole are located close to Earth's geographic poles. At the equator of the magnetic field, the magnetic-field strength at the surface is {{nowrap|3.05{{e|−5}} [[Tesla (unit)|T]]}}, with a [[magnetic dipole moment]] of {{nowrap|7.79{{e|22}} Am{{sup|2}}}} at epoch 2000, decreasing nearly 6% per century (although it still remains stronger than its long time average).<ref name="dipole">{{cite journal |last1=Olson |first1=Peter |last2=Amit |first2=Hagay |title=Changes in earth's dipole |url=https://pages.jh.edu/~polson1/pdfs/ChangesinEarthsDipole.pdf |journal=Naturwissenschaften |volume=93 |issue=11 |year=2006 |pages=519–542 |doi=10.1007/s00114-006-0138-6 |pmid=16915369 |bibcode=2006NW.....93..519O |s2cid=22283432}}</ref> The convection movements in the core are chaotic; the magnetic poles drift and periodically change alignment. This causes [[Geomagnetic secular variation|secular variation]] of the main field and [[geomagnetic reversal|field reversals]] at irregular intervals averaging a few times every million years. The most recent reversal occurred approximately 700,000 years ago.<ref name="fitzpatrick2006" /><ref name="campbelwh" />

The extent of Earth's magnetic field in space defines the [[magnetosphere]]. Ions and electrons of the solar wind are deflected by the magnetosphere; solar wind pressure compresses the dayside of the magnetosphere, to about 10 Earth radii, and extends the nightside magnetosphere into a long tail.<ref>{{Cite journal|last1=Ganushkina|first1=N. Yu|last2=Liemohn|first2=M. W.|last3=Dubyagin|first3=S.|date=2018|title=Current Systems in the Earth's Magnetosphere|url=https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2017RG000590|journal=Reviews of Geophysics|language=en|volume=56|issue=2|pages=309–332|doi=10.1002/2017RG000590|bibcode=2018RvGeo..56..309G|hdl=2027.42/145256|s2cid=134666611|issn=1944-9208|hdl-access=free|access-date=24 October 2020|archive-date=31 March 2021|archive-url=https://web.archive.org/web/20210331100349/https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017RG000590|url-status=dead}}</ref> Because the velocity of the solar wind is greater than the speed at which waves propagate through the solar wind, a supersonic [[bow shock]] precedes the dayside magnetosphere within the solar wind.<ref>{{cite web |url=http://sci.esa.int/jump.cfm?oid=40994 |title=Cluster reveals the reformation of the Earth's bow shock |publisher=European Space Agency |first=Arnaud |last=Masson |date=11 May 2007 |access-date=16 August 2016}}</ref> [[Charged particle]]s are contained within the magnetosphere; the plasmasphere is defined by low-energy particles that essentially follow magnetic field lines as Earth rotates.<ref>{{cite web |url=http://plasmasphere.nasa.gov/ |title=The Earth's Plasmasphere |publisher=NASA/Marshall Space Flight Center |last=Gallagher |first=Dennis L. |date=14 August 2015 |access-date=16 August 2016}}</ref><ref>{{cite web |url=http://plasmasphere.nasa.gov/formed.html |title=How the Plasmasphere is Formed |publisher=NASA/Marshall Space Flight Center |last=Gallagher |first=Dennis L. |date=27 May 2015 |access-date=16 August 2016 |archive-date=15 November 2016 |archive-url=https://web.archive.org/web/20161115064232/http://plasmasphere.nasa.gov/formed.html |url-status=dead }}</ref> The ring current is defined by medium-energy [[particle]]s that drift relative to the geomagnetic field, but with paths that are still dominated by the magnetic field,<ref name="BaumjohannTreumann1997">{{cite book |title=Basic Space Plasma Physics |publisher=World Scientific |first1=Wolfgang |last1=Baumjohann |first2=Rudolf A. |last2=Treumann |pages=8, 31 |year=1997 |isbn=978-1-86094-079-8}}</ref> and the [[Van Allen radiation belt]]s are formed by high-energy particles whose motion is essentially random, but contained in the magnetosphere.<ref name="Britannica">{{cite encyclopedia |url=https://www.britannica.com/science/ionosphere-and-magnetosphere/Magnetosphere |title=Ionosphere and magnetosphere |encyclopedia=Encyclopædia Britannica |publisher=Encyclopædia Britannica, Inc. |first=Michael B. |last=McElroy |year=2012}}</ref><ref name="Van Allen">{{cite book |title=Origins of Magnetospheric Physics |publisher=University of Iowa Press |last=Van Allen |first=James Alfred |date=2004 |isbn=978-0-87745-921-7 |oclc=646887856}}</ref>

During [[magnetic storm]]s and [[substorm]]s, charged particles can be deflected from the outer magnetosphere and especially the magnetotail, directed along field lines into Earth's ionosphere, where atmospheric atoms can be excited and ionized, causing the [[Aurora (astronomy)|aurora]].<ref name="stern2005" />