It is possible to use the heat of under the earth in volcanic
regions.
Cold water is pumped into earth and comes out as steam. Steam
can be used for heating or to power turbines creating electricity.
Potentially infinite energy supply.
Is used successfully in some countries, such as New Zealand.
Can be expensive to set up.
Only works in areas of volcanic activity. Geothermal
activity might calm down, leaving power station
redundant.
Dangerous underground gasses have to be disposed of
carefully.