How hot is it at 10000 feet, beneath the surface of the earth? What about 20000 feet?

Question

I wondered about how the temp. is rising as we venture depper in the earths crust.

Answer 1

It depends where you are. This will define the geothermal profile of the location
In volcanic area, the geothermal gradient can be as high as 100 deg celsius for 500 m.
Usually, in quiet sedimentary basin, the gradient is around 2.5 to 3.5 deg for 100 m.
To calculate the temperature at 10 000 ft or 20 000 ft, first you find the average temperature of the year and you consider that at 30 m (i.e. 100 ft), the temperature will not oscillate anymore. In Europe, one can take 15 deg celsius.
Then you take the geothermal gradient in celsius and multiply by the (depth-30)/100, depth being in m.
This gives for 10 000 ft between 96 and 128 celsius (204-262 deg Farenheit) and for 20 000 ft between 148 and 173 deg (298-343 deg Farenheit)

Answer 2

1 mile + 75 to 150 F
10,000 = about 2 miles TH4 150-300 F
20,000 = about 4 miles TH4 300-600 F
http://www.newton.dep.anl.gov/askasci/env99/env205.htm

Answer 3

That likely depends upon where you venture into the depths.