Geothermal Gradient


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geothermal gradient

[¦jē·ō¦thər·məl ′grād·ē·ənt]
(geophysics)
The change in temperature with depth of the earth.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Geothermal Gradient

 

the amount by which the temperature of rock rises per 100 meters’ increase in the depth of the deposits. The average gradient for crust depths that are accessible to direct temperature measurement is taken to be approximately 3° C. It varies from place to place as a function of the shape of the earth’s surface, thermal conductivity of the rock, subterranean water circulation, the proximity of volcanic foci, and the various chemical reactions taking place in the earth’s crust. The regular rise in temperature with increasing depth shows the existence of heat flow from the interior of the earth to its surface. The amount of this flow is equal to the product of the geothermal gradient and coefficient of thermal conductivity.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
The used available databases for possible impact factors, respectively, are stratum and lithology, structure characteristics, volcanic activities, water chemical characteristics, geothermal gradient, seismic activities, and hot water temperature.
where Z is the depth of geothermal water circulation, G is the reciprocal of the geothermal gradient (m/[degrees]C), Tz is the geothermal reservoir temperature ([degrees]C), [T.sub.0] is the annual average temperature of the recharge area ([degrees]C), and [Z.sub.0] is the depth of the local constant-temperature zone (m).
Geologists call this the Earth's "geothermal gradient", driven by heat produced at the Earth's core that radiates towards the crust.
The geothermal gradient, which is the difference in temperature between the core of the planet and its surface, drives a continuous conduction of thermal energy in the form of heat from the core to the surface.
The geothermal gradient of indicated prospective regions is above 58[degrees]C/km and the average in Slovakia is about 38[degrees]C/km.
With so much magma lying close to the surface, Iceland's geothermal gradient is unusually high.
The one big question in Kettler's mind is whether a high enough geothermal gradient exists underground to power massive electric generators.
As pointed out, for example, by Tinivella and Giustiniani [1], the understanding of gas hydrates, their stability, and relationship to overpressure conditions at its base, water depth, and geothermal gradient are very important, not only in the aspects of hazard potential.
It was contributed by the thinned out Earth crust (33 km in average), the geothermal heat flow density (83-111 mW/m2), and the high geothermal gradient (which is the highest in Vojvodina, 5.26 [degrees]C/100 m) which values are twice the European average.
A calculated P-T path for this kyanite-grade event in the Baltoro indicates that primitive garnet growth occurred on an initially high geothermal gradient (~30degC) followed by a near-isothermal rapid increase in pressure.
Further analysis was conducted with a numerical model to ac count for subsurface heterogeneity, the site geothermal gradient and the varying surface temperature.

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