You might want to read the guidelines again. Relevant things are "anything that gratifies one's intellectual curiosity."
Also, "Please don't submit comments complaining that a submission is inappropriate for the site. If you think something is spam or offtopic, flag it by going to its page and clicking on the "flag" link."
I, for one, didn't know before reading this that the temperature gradient is so large, about 25C/km. Being someone who, if I had to guess, has never been more than a hundred metres underground or so, I assumed it was about an order of magnitude lower than that.
The new Case Middle School buildings at Punahou (my alma mater) use something like that, but on a smaller scale. They freeze water at night when electricity is cheaper and then use it for cooling during the day.
Why not, when the mine is done, install a bunch of turbines in the shaft and pour a bunch of water down to 4km, send the steam back up to the top and voila! Endless power.
The fun part is remembering most of geothermal power is derived from nuclear decay. So really, it's nuclear power!
Of course, really, in the end everything is nuclear power. Sunlight (solar panels) is a byproduct of nuclear activity. Fossil fuels are plants that grew by the light of the sun; wind is a result of heating of the atmosphere by the sun, and hydroelectric is a result of heating of the ocean by the sun.
(stretching, I know)... yet the power systems use something more than hydrogen and helium so are made of fusion byproducts from stars. ("We are all starstuff.")
I think a really important distinction is between things that are really interesting, and things that are "interesting" mostly because they confirm one's political beliefs. This article is just a random, interesting (or not, depending on your tastes) article that is not going to beget discussions involving taxes, the tea party, Obama, Ayn Rand, the Gold Standard, or any number of other discussions that have been done over and over and over and over again on the internet.
