Since energy sources matter so much, we need a source that can give us clean energy, low carbon emissions, no volatile substances released, and something that is preferably naturally occurring. So far, geothermal energy fits those requirements.

Geothermal energy is captured by using the steam from the convection currents in the mantle of the earth. However, some of the plants drill into the earth, through the crust. If we didn't drill to harvest the geothermal energy, it would be a much better source. The problem with drilling is it is cracking the earth, but since we don't have much choice for energy it may be one of our only hopes. I hate sacrificing things for other things, but it's much better than some of the other terrible mutilations to the earth, like fracking and drilling for oil.

We may be able to depend on this source, until the human population grows too much.

This source is alright. Let's make this more common.