[mertle]

Very interesting.

link about geothermal energy

http://en.wikipedia.org/wiki/Geothermal_energy

however this info

Even though geothermal power is globally sustainable, extraction must still be monitored to avoid local depletion

Geothermal energy is classified as a renewable resource,
where “renewable” describes a characteristic of the resource:
the energy removed from the resource is continuously replaced
by more energy on time scales similar to those required for
energy removal. Consequently, geothermal exploitation is not
a “mining” process. Geothermal energy can be used in a “sustainable”
manner, which means that the production system applied
is able to sustain the production level over long periods of
time. The longevity of production can be secured and sustainable
production achieved by using moderate production rates,
which take into account the local resource characteristics (field
size, natural recharge rate, etc.).

http://geoheat.oit.edu/bulletin/bull28-3/art2.pdf