Iceland’s decision to harness the heat inside the earth in a process known as geothermal energy dates back to the 1970s and the oil crisis.

But the new geothermal well is expected to generate far more energy, as the extreme heat and pressure at that depth makes the water take the form of a “supercritical” fluid, which is neither gas nor liquid.

Source: Iceland drills 4.7 km down into volcano to tap clean energy