Landsvirkjun, which had paid for most of the I.D.D.P. work, decided that it needed financial support to drill more exploratory wells. “We said, ‘We’re just a small energy company in Iceland,’ ” Palsson told me. But it made its research available to the international scientific community, and there has been intermittent interest from the U.K., Germany, Canada, and New Zealand. “That’s where we are now, trying to fund it as a science project that can also benefit the energy industry,” Palsson said.

Driving back to the airport, we saw snow ptarmigans and cairns of black stones marking trails that stretched beyond view. Iceland’s transition into a country powered nearly completely by renewables can seem fantastical, and the landscape furthers this impression. Because Iceland is singular in so many ways—that lonely arctic-char species! those small horses with their tölt!—you can get the feeling that geothermal energy is a niche endeavor, as opposed to one that is technically and economically feasible in places where volcanic eruptions aren’t part of the daily forecast. But that feeling is outdated and misleading.

Geothermal is underdeveloped, and its upfront costs can be high, but it’s always on and, once it’s set up, it is cheap and enduring. The dream of geothermal energy is to meet humanity’s energy demands affordably, without harnessing horses for horsepower, slaughtering whales for their oil, or burning fossil fuels. The planet’s heat could be used to pasteurize milk or heat dorm rooms or light up a baseball stadium for a night game.

At more than five thousand degrees Celsius, the Earth’s core is roughly as hot as the surface of the sun. At the Earth’s surface, the temperature is about fourteen degrees. But in some places, like Iceland, the ground underfoot is much warmer. Hot springs, geysers, and volcanoes are surface-level signs of the Earth’s inferno. Dante’s description of Hell is said by some to have been inspired by the landscape of sulfurous steam plumes found in Devil’s Valley in Tuscany.

Snow monkeys and humans have been using Earth-heated waters as baths for ages. In the Azores, a local dish, cozido de las furnas, is cooked by burying a clay pot in hot volcanic soil; in Iceland, bread is still sometimes baked this way. The first geothermal power generator was built in Devil’s Valley, in 1904, by Prince Piero Ginori Conti of Trevignano, who had been extracting borax from the area and thought to make use of the steam emerging from the mining borehole. The generator initially powered five light bulbs. Not long afterward, it powered central Italy’s railway system and a few villages. The geothermal complex is still in operation today, providing one to two per cent of Italy’s energy. In the United States, the first geothermal plant was built in 1921, in Northern California, in a geyser-filled area that a surveyor described as the gates of Hell. That plant powered a nearby resort hotel and is also still in use.

“So, anyway, tell me something about yourself.”

Cartoon by Avi Steinberg

There aren’t gates of Hell just anywhere. A kilometre below ground in Kamchatka is considerably hotter than a kilometre below ground in Kansas. There is also readily accessible geothermal energy in Kenya (where it provides almost fifty per cent of the country’s energy), New Zealand (about twenty per cent), and the Philippines (about fifteen per cent)—all volcanic areas along tectonic rifts. But in less Hadean landscapes the costs and uncertainties of drilling deep in search of sufficient heat have curtailed development. This partly explains why, in the field of clean energy, geothermal is often either not on the list or mentioned under the rubric of “other.” For decades, both private and government investment in geothermal energy was all but negligible.

That has now changed. In the past five years, in North America, more than a billion and a half dollars have gone into geothermal technologies. This is a small amount for the energy industry, but it’s also an exponential increase. In May, 2021, Google signed a contract with the Texas-based geothermal company Fervo to power its data centers and infrastructure in Nevada; Meta signed a similar deal with Texas-based Sage for a data center east of the Rocky Mountains, and with a company called XGS for one in New Mexico. Microsoft is co-developing a billion-dollar geothermal-powered data center in Kenya; Amazon installed geothermal heating at its newly built fulfillment center in Japan. (Geothermal energy enables companies to avoid the uncertainties of the electrical grid.) Under the Biden Administration, the geothermal industry finally received the same kind of tax credits given to wind and solar, and under the current Trump Administration it has received the same kind of fast-track permitting given to oil and gas. Donald Trump’s Secretary of Energy, Chris Wright, spoke at a geothermal conference and declared, in front of a MAGA-like sign that read “MAGMA (Making America Geothermal: Modern Advances),” that although geothermal hasn’t achieved “liftoff yet, it should and it can.” Depending on whom you speak with, either it’s weird that suddenly everyone is talking about geothermal or it’s weird that there is a cost-competitive energy source with bipartisan appeal that no one is talking about.

Scientific work that has been discarded or forgotten can return—sometimes through unknowing repetition, at other times through deliberate recovery. In the early nineteen-seventies, the U.S. government funded a program at Los Alamos that looked into developing geothermal energy systems that didn’t require proximity to geysers or volcanoes. Two connected wells were built: in one, water was sent down into fractured hot, dry rock; from the other, the steam that resulted from the water meeting the rock emerged. In 1973, Richard Nixon announced Project Independence, which aimed to develop energy sources outside of fossil fuels. “But when Reagan came into office, he changed things,” Jefferson Tester, a professor of sustainable energy systems at Cornell University, who was involved in the Los Alamos project, told me. The price of oil had come down, and support for geothermal dissipated. “People got this impression that it was a failure,” Tester said. “I think if they looked a little closer, they would see that a lot of the knowledge gained in those first years could have been used to leverage what is happening now.”