While modern scientific advancements present humankind with no shortage of technological marvels, people the world over are still awed by the eons-old power of natural forces. While the sheer energy of these forces is perhaps best evidenced by the destructive force of natural disasters, it also takes many forms that have proven far more useful to humanity. Hydroelectric and hydrokinetic mechanisms have existed in some form since the earliest days of civilization, and windmills have farmed the skies for almost as long, drawing power to grind flour and pump water. Solar energy dried clothes and baked the mud bricks that became the foundation of many a civilization.

But until recently, one natural force has largely eluded the human yoke. Just beneath the surface of the Earth, tremendous pressures and the continual decay of radioactive elements create a tremendous amount of heat. Only occasionally visible on the surface—in places such as Iceland, where direct geothermal power warms a vast majority of the homes—geothermal power tends to reveal itself in violent explosive ways, such as volcanoes and geysers. Despite this, though, the geothermal resource is one of the most potent and untapped power sources available to the inhabitants of this planet.

Unlike many traditional energy sources, such as shallow coal and oil, geothermal can be difficult to tap because of its depth. But within roughly 30,000 feet of the Earth’s surface, there is 50,000 times the amount of energy contained in the world’s combined fossil fuel resources, and scientists have developed several methods of cracking this energy nut. The most common involves finding an existing location where cold water seeps down into the hotter parts of the earth, before being forcefully blasted back up the surface as steam. Though effective (the Geysers plant in California delivers some 850 megawatts), the usefulness of this method diminishes as more plants tap an area, thus decreasing the pressure, and they occasionally release hazardous and foul-smelling gasses.

A second method for harvesting geothermal energy involves pumping cold water down to the heated regions of the earth, and harvesting energy from it as it returns in superheated state. Though untested on a large scale, this method would largely eliminate problems of noxious gasses and water pressure, and test sites have thus far yielded good results. Programs in the United States and at least four other nations are currently attempting to further refine this hot, dry rock method of generating geothermal power.

Until these technologies are proven on a wider scale, though, geothermal power’s most effective role in solving the world’s energy problem is as a heater of homes and other small structures. Even a few feet below the soil, temperatures in the ground rarely dip below 50 degrees Fahrenheit . By running pipes through this warm soil, and passing a fluid through those pipes, warmth can be carried back up to structures above ground level, providing carbon-free heat through even the coldest of months.