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Earth's internal heat budget

Global map of the flux of heat, in mW/m2, from Earth's interior to the surface.[1] The largest values of heat flux coincide with mid-ocean ridges, and the smallest values of heat flux occur in stable continental interiors.

Earth's internal heat budget is fundamental to the thermal history of the Earth. The flow of heat from Earth's interior to the surface is estimated at 47±2 terawatts (TW)[1] and comes from two main sources in roughly equal amounts: the radiogenic heat produced by the radioactive decay of isotopes in the mantle and crust, and the primordial heat left over from the formation of Earth.[2]

Earth's internal heat travels along geothermal gradients and powers most geological processes.[3] It drives mantle convection, plate tectonics, mountain building, rock metamorphism, and volcanism.[2] Convective heat transfer within the planet's high-temperature metallic core is also theorized to sustain a geodynamo which generates Earth's magnetic field.[4][5][6]

Despite its geological significance, Earth's interior heat contributes only 0.03% of Earth's total energy budget at the surface, which is dominated by 173,000 TW of incoming solar radiation.[7] This external energy source powers most of the planet's atmospheric, oceanic, and biologic processes. Nevertheless on land and at the ocean floor, the sensible heat absorbed from non-reflected insolation flows inward only by means of thermal conduction, and thus penetrates only a few dozen centimeters on the daily cycle and only a few dozen meters on the annual cycle. This renders solar radiation minimally relevant for processes internal to Earth's crust.[8]

Global data on heat-flow density are collected and compiled by the International Heat Flow Commission of the International Association of Seismology and Physics of the Earth's Interior.[9]

  1. ^ a b Davies, J.H.; Davies, D.R. (22 February 2010). "Earth's surface heat flux". Solid Earth. 1 (1): 5–24. Bibcode:2010SolE....1....5D. doi:10.5194/se-1-5-2010.
  2. ^ a b Cite error: The named reference Turcotte was invoked but never defined (see the help page).
  3. ^ Buffett, B. A. (2007). Taking Earth's temperature. Science, 315(5820), 1801–1802.
  4. ^ Morgan Bettex (25 March 2010). "Explained: Dynamo Theory". MIT News.
  5. ^ Kageyama, Akira; Sato, Tetsuya; the Complexity Simulation Group (1 January 1995). "Computer simulation of a magnetohydrodynamic dynamo. II". Physics of Plasmas. 2 (5): 1421–1431. Bibcode:1995PhPl....2.1421K. doi:10.1063/1.871485.
  6. ^ Glatzmaier, Gary A.; Roberts, Paul H. (1995). "A three-dimensional convective dynamo solution with rotating and finitely conducting inner core and mantle". Physics of the Earth and Planetary Interiors. 91 (1–3): 63–75. Bibcode:1995PEPI...91...63G. doi:10.1016/0031-9201(95)03049-3.
  7. ^ Archer, D. (2012). Global Warming: Understanding the Forecast. ISBN 978-0-470-94341-0.
  8. ^ Lowrie, W. (2007). Fundamentals of geophysics. Cambridge: CUP, 2nd ed.
  9. ^ www.ihfc-iugg.org IHFC: International Heat Flow Commission – Homepage. Retrieved 18/09/2019.
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