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Geothermal gradient is the rate of change in temperature with respect to increasing depth in Earth's interior. As a general rule, the crust temperature rises with depth due to the heat flow from the much hotter mantle ; away from tectonic plate boundaries , temperature rises in about 25–30 °C/km (72–87 °F/mi) of depth near the surface in ...
In polar regions, due to low temperatures, the upper limit of the hydrate stability zone occurs at a depth of approximately 150 meters. 1 [citation needed] The maximal depth of the hydrate stability zone is limited by the geothermal gradient. Along continental margins the average thickness of the HSZ is about 500 m. [3]
Outside of the seasonal variations, the geothermal gradient of temperatures through the crust is 25–30 °C (77–86 °F) per km of depth in most of the world. The conductive heat flux averages 0.1 MW/km 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 ...
Geothermal energy – Thermal energy generated and stored in the Earth; Geothermal gradient – Rate of temperature increase with depth in Earth's interior; Geothermal heating – Use of geothermal energy for heating; Geothermal power – Power generated by geothermal energy
The increase in temperature with increasing depth is known as the geothermal gradient and is gradual within the rheological boundary layer. In practice, the RBL is defined by the depth at which the viscosity of the mantle rocks drops below ~ 10 21 P a ⋅ s . {\displaystyle 10^{21}Pa\cdot s.} .
The geothermal gradient can be lowered where cool material from the surface sinks downward, increasing the strength of the surrounding mantle, and allowing earthquakes to occur down to a depth of between 400 km (250 mi) and 670 km (420 mi). [27] The pressure at the bottom of the mantle is ~136 GPa (19,700,000 psi; 1,340,000 atm). [28]
As a result, the lower mantle's temperature gradient as a function of depth is approximately adiabatic. [1] Calculation of the geothermal gradient observed a decrease from 0.47 kelvins per kilometre (0.47 °C/km; 1.4 °F/mi) at the uppermost lower mantle to 0.24 kelvins per kilometre (0.24 °C/km; 0.70 °F/mi) at 2,600 kilometres (1,600 mi). [3]