Atmospheric pressure underground?

[Shackleford]

As you go deeper underground, to calculate the total pressure at the subterranean point, would you sum the atmospheric weight plus the weight of the overlying soil? How does this work exactly? Thanks.

 

[mgb_phys]

Depends what you are trying to calculate.
The air pressure (in a mine or tunnel) will increase, just like it decreases when you go higher, you add the surface atmospheric pressure to the extra weight of the column of air between you and the surface.
The pressure in the rock underground is the weight of the rock column above you - you can probably ignore the air weight compared to the weight of rock.

 

[russ_watters]

Since the atmosphere doesn't penetrate the ground, you just add 14.7 to the pressure due to the weight of the earth.