Geothermal gradien
Geothermal gradient
Geothermal gradient is the rate of increasing temperature with respect to increasing depth in the Earth's interior. Away from tectonic plate boundaries, it is 22.1°C per km of depth (1°F per 70 feet of depth) in most of the world.[1] Strictly speaking,geo-thermal necessarily refers to the Earth but the concept may be applied to other planets. The Earth's internal heat comes from a combination of residual heat from planetary accretion (about 20%) and heat produced through radioactive decay(80%).[2] The major heat-producing isotopes in the Earth are potassium-40, uranium-238, uranium-235, and thorium-232.[3] At the center of the planet, the temperature may be up to 7,000 K and the pressure could reach 360 GPa.[4] Because much of the heat is provided by radioactive decay, scientists believe that early in Earth history, before isotopes with short half-lives had been depleted, Earth's heat production would have been much higher. Heat production was twice that of present-day at approximately 3 billion years ago,[2] resulting in larger temperature gradients within the Earth, larger rates of mantle convectionand plate tectonics, allowing the production of igneous rocks such as komatiites that are not formed anymore today
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