Editing Earth's outer core (section)

=== Implications for Earth's magnetic field ===
[[File:Dynamo Theory - Outer core convection and magnetic field generation.svg|alt=A diagram of Earth's geodynamo and magnetic field, which could have been driven in Earth's early history by the crystallization of magnesium oxide, silicon dioxide, and iron(II) oxide. Convection of Earth's outer core is displayed alongside magnetic field lines.|thumb|A diagram of Earth's geodynamo and magnetic field, which could have been driven in Earth's early history by the crystallization of [[magnesium oxide]], [[silicon dioxide]], and [[iron(II) oxide]].]]

[[Earth's magnetic field]] is driven by [[convection (heat transfer)|thermal convection]] and also by chemical convection, the exclusion of light elements from the inner core, which float upward within the fluid outer core while [[density|denser]] elements sink.<ref name=":7" /><ref name=":6">{{Cite journal |last=Buffett |first=Bruce A. |date=2000-06-16 |title=Earth's Core and the Geodynamo |url=https://www.science.org/doi/abs/10.1126/science.288.5473.2007 |journal=Science |volume=288 |issue=5473 |pages=2007–2012 |language=EN |doi=10.1126/science.288.5473.2007|pmid=10856207 |bibcode=2000Sci...288.2007B }}</ref> This chemical convection releases [[gravitational energy]] that is then available to power the [[dynamo theory|geodynamo]] that produces Earth's magnetic field.<ref name=":6" /> [[Carnot cycle|Carnot efficiencies]] with large uncertainties suggest that compositional and thermal convection contribute about 80 percent and 20 percent respectively to the power of Earth's geodynamo.<ref name=":6" /> Traditionally it was thought that prior to the formation of [[Earth's inner core#Age|Earth's inner core]], Earth's geodynamo was mainly driven by thermal convection.<ref name=":6" /> However, recent claims that the [[thermal conductivity]] of [[iron]] at core [[temperature]]s and pressures is much higher than previously thought imply that core cooling was largely by conduction not convection, limiting the ability of thermal convection to drive the geodynamo.<ref name=":0" /><ref name=":7" /> This conundrum is known as the new "core paradox."<ref name=":0" /><ref name=":7" /> An alternative process that could have sustained Earth's geodynamo requires Earth's core to have initially been hot enough to dissolve [[oxygen]], [[magnesium]], [[silicon]], and other light elements.<ref name=":7" /> As the Earth's core began to cool, it would become [[supersaturation|supersaturated]] in these light elements that would then [[precipitation (chemistry)|precipitate]] into the [[Lower mantle (Earth)|lower mantle]] forming [[oxide]]s leading to a different variant of chemical convection.<ref name=":0" /><ref name=":7" />

The magnetic field generated by core flow is essential to protect life from interplanetary radiation and prevent the atmosphere from dissipating in the [[solar wind]]. The rate of cooling by conduction and convection is uncertain,<ref>{{cite web |url=https://www.nbcnews.com/science/science-news/earths-core-cooling-faster-previously-thought-researchers-say-rcna12732 |title=Earth's core cooling faster than previously thought, researchers say |date=19 January 2022 |author=David K. Li |publisher=[[NBC News]]}}</ref> but one estimate is that the core would not be expected to freeze up for approximately 91 billion years, which is well after the Sun is expected to expand, sterilize the surface of the planet, and then burn out.<ref>{{cite web |url=https://education.nationalgeographic.org/resource/core/ |access-date=15 July 2024 |title=Core |publisher=[[National Geographic]]}}</ref>{{better source needed|date=July 2024}}