North Milford Valley, in western Utah, is home to dormant volcanoes, subterranean lava deposits, and smatterings of obsidian—black volcanic glass—that Paiute peoples once collected for arrowheads and jewelry. Scalding groundwater still bubbles to the surface in places. In such a landscape, you remember that the planet’s hard exterior, where we spend our entire lives, is so thin that we call it a crust. Its superheated interior, meanwhile, burns with an estimated forty-four trillion watts of power. Milford was once a lead-, silver-, and gold-mining town, but when I visited the area on a sunny spring morning a scientist named Joseph Moore was prospecting for something else: heat.

Heat mined from underground is called geothermal—“earth heat,” in ancient Greek—and can be used to produce steam, spin a turbine, and generate electricity. Until recently, humans have tended to harvest small quantities in the rare places where it surfaces, such as hot springs. Moore’s mission, as a geologist at the University of Utah and the project leader of the Frontier Observatory for Research in Geothermal Energy (FORGE), is to “develop the roadmap that is needed to build geothermal reservoirs anywhere in the world.” This road is long, and much of the map remains blank. The biggest problem is drilling miles through hot rock, safely. If scientists can do that, however, next-generation geothermal power could supply clean energy for eons.

During my trip, Moore’s corps of consultants and roughnecks were drilling the fifth borehole of their experimental project. Their rig, armed with a diamond drill bit, towered like a rocket over the rural landscape; miles of solar panels and wind turbines receded into the distance. The hole, which would eventually be L-shaped, was five thousand feet deep, and the team had another five thousand to go, horizontally. But, before they could drill any farther, they needed to install a hundred-and-fifty-ton steel tube in the hole, using special heat-resistant cement to glue it into place. The tube was like a massive straw that was meant to transport hot water and steam from an artificial underground reservoir—without contaminating local groundwater or triggering earthquakes.

At 6:15 P.M. on May 3rd, cement had started flowing into the hole. Four hours later, part of the cement folded in on itself. The next morning, the cement supply ran out; the men had miscalculated how much they needed. This brought the three-hundred-million-dollar operation to a maddening halt. Moore, in bluejeans and a FORGE-branded hard hat, called his supplier. The nearest batch of suitable cement was five hundred miles away, in Bakersfield, California. The truck would not arrive until after dark.

Right now, geothermal energy meets less than one per cent of humanity’s electricity and heating needs—a puny, almost irrelevant portion. Fossil fuels power about eighty per cent of human activity, pumping out carbon dioxide and short-circuiting our climate to catastrophic effect. Converts argue that geothermal checks three key boxes: it is carbon-free, available everywhere, and effectively unlimited. Crucially, it is also baseload, which means that, unlike solar panels or wind, it provides a constant flow of energy. Companies and governments have taken notice. “Over the last two years, I have watched this exponential spin-up o