Can U Solve It: Coudersport Ice Mine?

Coudersport Ice Mine (in PA):
The Mine forms Icicles in hot weather; but bone dry by winter!

Check these links out for reference:

INE.html

Here's a POP quiz for us hollow earth geniuses!
How DOES that happen?
Whoever knows this, you sure must've not told anyone else!
IF you do know, have you considered joining Mensa?

I threw this question to all, so that by giving all of us the
unequivocal answer to this crystal problem, we'd all have a
better insight to this hollow earth thing.

It's a stumper to me.
I'm waiting to see some bright person solve it in 5 seconds...

...by the way, we'll all probably wonder how you knew the answer too.

Feel free to post the difficult questions.
Thinking is good exercise, huh?