[Bert Latamore (OP)]

This question applies to the recent discussion of alternative energy on The Naked Scientists podcast, but equally to other coverage of this topic on other podcasts & media that I have heard going back for years. Iceland powers its entire country with geothermal. Europe has a huge potential source at Mt. Etna. North America similarly has Yellowstone. Geothermal is here today, it is safe, it is 24X7X360, and it is pollution-free. Why is it not even mentioned?

[Bored chemist]

Because it only works in a very few places and, by the way, it isn't pollution free.

[charles1948]

Because it only works in a very few places and, by the way, it isn't pollution free.

Also because there's still plenty of oil to make petrol to fuel our cars.  Even when the oil runs out, there's hydrogen.

But how could cars be powered by "geothermal energy"?

[Bored chemist]

Even when the oil runs out, there's hydrogen.

There are no hydrogen mines.

But how could cars be powered by "geothermal energy"?

Use the heat to generate steam, use that to spin a turbine, use that to drive a generator and use the electricity to electrolyse water to make hydrogen or charge batteries.

Pretty much the same way as we use nuclear power.

[charles1948]

If we start using "geothermal" energy to fuel our cars, employing the indirect methods that BC has pointed out, won't this inevitably cause some cooling of the Earth's interior.  As we suck its heat from it.

Then as the interior cools, it must also contract  and shrink. Thus opening widening gaps between the inner part of the Earth, and the outer crust that we live on.

If such gaps should develop,  won't the the crust, deprived of support, respond by starting to collapse inwards.

Resulting in crustal phenomena such as massive earthquakes?

[Bored chemist]

t, won't this inevitably cause some cooling of the Earth's interior.

The Earth's core is already cooling.
We aren't exactly sure at what rate.
Much of the heat comes from radioactive decay and we won't change the rate of that.

[Petrochemicals]

If you remove significant amounts of energy from the crust of the earth you will have a thickening and this will cause far more severe and frequent earthquakes. The earth does not emmit enough energy to sustain the population at present.