What is the deepest mine or cave in the US?

Question

And can anyone tell me how fast the temperature changes the deeper you travel underground?

Answer 1

The deepest mine is the (now closed) Homestake Mine in Lead, South Dakota. I forget the exact depth but it was several miles below the surface.

Temperature change in extremely deep caves or mines is related to local heat flow. There are parts of the earth's surface that have higher heat flow than others.

Simply put, when you go down from a few tens to a few hundred feet the temperature will be stable at about 55 degrees F. If you go into the many hundreds of feet (almost always a mine) you'll likely start to heat up.

Mines in Virgina City, NV 150 years ago would have a cold room where they put blocks of ice for the miners to take breaks from the oppressive heat of the tunnel. The gold mines in South Africa are down to depths of over nine miles and have extensive systems of air pumps to cool and circulate breathable air to that depth. It's very hot down there.

Answer 2

The deepest cave in the United States is the Kazumura Cave in the state of Hawaii