[Dr. Scott W. Tinker] Geothermal energy, the heat of the Earth, can be found beneath our feet everywhere. But extracting enough of it at an affordable price is the challenge. In some parts of the world extreme heat from deep within the Earth rises nearer the surface. Here, it's fairly easy to tap. For more on how that's done, see our geothermal cycles. We use that heat in mainly two ways, to heat people's homes and to turn a steam turbine to make electricity. Like hydropower, geothermal is flexible. It can be always on base load power. Or it can be ramped up quickly to follow demand. The problem is these high temperature geothermal areas are few and far between. Iceland is the best example, but Indonesia, Italy, California, and Hawaii all have a powerful geothermal resource. So how do we get these benefits elsewhere? In some places old oil wells allow access to hot water. In others we're experimenting with drilling new wells, fracturing the rocks, and circulating water. But the energy returned is low while the cost is high. There's also low temperature geothermal, which uses the constant temperature on the near surface to heat or cool a building. Its applications are broad, but in most places, it's still more expensive than other options. So that's geothermal in a nutshell. Where there's high temperature near the surface it's a fantastic resource. Elsewhere, it's still cost prohibitive. To see Iceland's success with geothermal electricity, check out the film.