Geothermal Energy is Abundant

Geothermal Energy is heat energy created by the molten rock beneath our Earth's crust. It is turned into electricity by the same method as a coal, natural gas, or nuclear energy--namely heated steam turning a turbine to induce a current in wire.

Source: http://en.wikipedia.org/wiki/Geothermal_gradient

Above is an image dissecting the different layers of the Earth. The crust layer is what protects us from the geothermal energies deep beneath. The crust is only 5 km to 30 km thick. Temperatures in the crust range between 392 °F to 752 °F.¹ No drilling project has ever gone very far below 20 km, but if we were able to drill to the upper mantle, we would have access to geothermal temperatures between 932° and 1,652 °F.²

The temperature in the crust reliably increases by 25° C every 1 km we drill downwards.³ Geothermal power plants only need temperatures ranging from 57° C to 180° C, to operate, although temperatures above 180° will increase efficiency. Nevertheless, following the 25° C every 1 km model, we would only need to drill 2-3 km down to get operating geothermal range.

Temperature gradient increasing as the depth increases.
Source: http://en.wikipedia.org/wiki/Geothermal_gradient

There's enough heat energy stored under all of us, at any point in the world, for everyone to theoretically have their own backyard geothermal power plant. Even the most impoverished countries have access to this resource, immediately under them, if someone were to drill deep enough.

Granted, with present technology it would be more expensive to do all the drilling than using our already available solar, wind, and coal resources, but the most important point is the energy exists. Though it would be more expensive to utilize with current technologies than other energy alternatives, the energy is nevertheless accessible to us with present technologies.

It should be reassuring that if the sun were to disappear overnight, and the oil rigs and coal mines stopped working, we would still have near-limitless energy right underneath us.

- Notes - 

All sources were derived from the corresponding Wikipedia articles which follow: Mantle (geology), Crust (geology), and Geothermal Gradient. Copyright Wikimedia Foundation, 2014.