Temperature vs. Depth
Date: November 28, 2002
How hot is the earth at a depth of 1 mile? I know there
is a constant calculable formula for temperature as you go deeper and
deeper. Therefore the temp in a cave or well or archeological dig should
be an exact answer, and I would like to know what that is.
The rate of change of temperature with depth is referred to as the
geothermal gradient. The geothermal gradient varies depending on location,
so there is no uniform answer. On average, the geothermal gradient is
approximately 75 degrees F per mile. In volcanically active areas, the
gradient can be as high as 150 degrees F per mile. In ocean trenches, the
gradient may be as low as 15 degrees F per mile. Decay of naturally
occurring radioactive elements may also cause localized increases in
temperature in some locations.
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