Encyclopedia of Astrobiology

Living Edition
| Editors: Muriel Gargaud, William M. Irvine, Ricardo Amils, Henderson James Cleaves, Daniele Pinti, José Cernicharo Quintanilla, Michel Viso

Geothermal Gradient

Living reference work entry
DOI: https://doi.org/10.1007/978-3-642-27833-4_643-3

Definition

A geothermal gradient is the increase in temperature with increasing depth beneath the Earth’s surface. This gradient is due to outward heat flow from a hot interior. The Earth’s internal heat derives from a combination of residual heat from planetary accretion (20 %) and heat produced through radioactive decay of U, Th, and K (80 %). The magnitude of the geothermal gradient depends on the rate of heat production at depth, the dynamics of the system, and the conductivity of rocks. The highest gradients, 40–80 K km−1, are measured at oceanic spreading centers (mid-ocean ridges) or at island arcs where magma is close to the surface. The lowest gradients occur at subduction zones where cold lithosphere descends into the mantle. The gradient in old stable continental crust is ~30 K km−1 and is somewhat lower in cratons. Upwelling parts of the mantle ascend nearly adiabatically (i.e., they lose little to no heat to the surroundings), and the gradient is very low, about 0.3 K km−1....

Keywords

Heat Transfer Heat Flow Continental Crust Subduction Zone Internal Heat 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  1. 1.Maison des GéosciencesLGCA, Université J. FourierSt-Martin d’HèresFrance