Iceland is like nowhere else on Earth.

Sitting at the edge of the Arctic Circle and on top of the Mid-Atlantic Range—the intersection of the Eurasian and North American tectonic plates—it is a real-life land of ice and fire, and the two elements collide in ways that are spectacular to behold.

The approach to Iceland’s international airport in Keflavík offers a sudden introduction to why so many tourists visit the island each year: At sunrise, the low-angled light flickers across the ocean, lighting up colossal glaciers and steaming volcanoes, before the plane drops in altitude, skims above moss-topped lava fields, and lands roughly on a gusty runway in the middle of nowhere.

But tourism isn’t the only thing that Iceland cultivates with its natural phenomena. In recent decades, it has learned to tap its unique geography to generate power.

“Welcome,” says the sign in the airport, “to the land of renewable energy.”

It’s not just a slogan. One hundred percent of Iceland’s electricity and heat are drawn from renewable sources. Nine out of ten homes are heated geothermally, making this tiny nation the world’s largest-per-capita green energy producer and largest-per-capita electricity producer.

This wasn’t always the case. Until the 1970s, the country was almost wholly reliant on imported fossil fuels to power its cars, trucks, and fishing trawlers—the centerpiece of its economy—and to heat its homes against the arctic cold. When oil prices surged during the OPEC embargo, Iceland did not have enough domestic fossil fuel to sustain them through the crisis.

What they did have were ice and fire, resulting in a decades-long plan to convert these natural resources into an endless supply of power.

Glaciers cover 11 percent of Iceland’s landmass, giving it a constant flow of streams that rush into larger glacial rivers—a naturally sustainable system that’s perfect for feeding hydroelectric dams.

A glacier is any area where snow accumulates more quickly than it melts, over a sustained period of time; it’s a giant slab of permanent ice always piling more on top while melting on its bottom. Iceland started using dams to generate electricity as far back as 1904, but all its early plants were shuttered during the Great Depression. Only after World War II did hydropower become economically viable again, developing rapidly over the second half of the 20th century. Now the island’s gushing rivers generate more than three-fourths of its electricity, and Iceland is home to the largest hydroelectric plant in Europe, Fjótsdalsstöð, at the Kárahnjúkar Dam.

But where Iceland has become a real world leader is in geothermal power, because it is a “high island,” one that only exists because of volcanic activity. The two pieces of the Earth’s crust that intersect at the Mid-Atlantic Ridge are slowly pulling apart, opening rifts that bubble forth with molten rock. Over time, the rock cools and grows into an island, the reason why the country continues to expand at a rate of one inch per year.

The effects of living in this sort of environment are extreme: Iceland has over two hundred active volcanoes and experiences roughly five hundred earthquakes every week. It also has a lot of hot water, over six hundred natural springs heated by geothermal activity. These are a big part of why people settled there in the first place, and continue to be some of its biggest tourist attractions.

To help combat the cost of heating buildings with fossil fuels, Iceland began channeling geothermal water into the homes of its towns and cities. In Reykjavik, hot water from the tap stinks of sulfur, because it comes directly from volcanic hot springs. The water runs through pipes underneath streets and sidewalks, its heat keeping them clear of snow and ice.

Hot spring-derived water saves Iceland a significant amount of electricity, but can’t generate it. Real geothermal power comes from another, deeper source. Geologists have identified more than thirty “high-temperature geothermal fields”—natural reservoirs of water that have been heated by the Earth’s mantle to 500 degrees or more—higher than the melting point of lead. This super-heated water is now being used to generate electricity at five different power plants throughout Iceland, spinning steam turbines to create 7 terrawatt hours of completely renewable power. And there’s more to come: these plants are currently operating at just a fraction of their theoretical capacity.

Iceland’s ability to generate cheap, renewable electricity is attracting diverse, power-intensive industries like aluminum smelting and data hosting, and providing whole new engines to the island’s economy. Since 2011, its GDP has doubled. In an effort to export this type of energy, Landsvirkjun, the National Power Company of Iceland, has drafted a plan to connect its power grid with Scotland via a submarine cable under the Atlantic Ocean.

But the most valuable export may be their expertise. Many nations are eager to replicate the total transition from fossil fuel dependence to sustainable, renewable power, and want to know more about how to implement geothermal solutions. So far the Icelandic energy industry has teamed up with more than fifty countries on construction projects around the world. One of the newest, and largest, geothermal district heating systems warms a million homes in Paris. Geothermal: it’s not just for volcanoes anymore.

Geothermal energy currently provides less than 1 percent of the world’s electricity, but the World Energy Council has estimated this number could increase eightfold or more in the coming years. Nearly forty countries sit in geothermal-rich territory, and developing nations in Africa, Latin America, and the Pacific could use it to fill all of their electrical needs.

Although the United States has vast natural geothermal resources, particularly in its Western states (which sit on the Pacific “Ring of Fire”), currently only 0.3 percent of American electricity comes from geothermal—one of the lowest shares in any developed nation despite the obvious and growing need for cheap, clean, renewable energy. The Trump administration has made fossil fuels its priority.

Ironically, though, it may be oil companies that provide the next breakthroughs needed to bring geothermal into the mainstream. They are the ones with the most experience at deep drilling and creating technology able to withstand the Earth’s extreme natural heat.

The world will run out of fossil fuels sooner or later. Meanwhile, if there’s anything we know about volcanoes, it’s that they are, ultimately, unstoppable. Hopefully the power we can harness from their energy will be unstoppable, too.