In Rotorua, New Zealand, the evidence of geothermal activity is everywhere. Often, the grates covering street drains will steam. Every now and again, a homeowner will wake up to find that their backyard has been replaced by a steaming hole in the ground. But all of this was nearly lost in my youth thanks to humanity’s attempts to tap into it. Geothermal fields cannot be endlessly plundered, it turns out.

But this is a good-news story. Geothermal activity, in 2017, supplies some 17-18 percent of New Zealand’s electricity. But there are many places in the world that have volcanoes, and many of them are more active than New Zealand’s. In New Zealand, geothermal fields cover sleeping volcanoes, not the restless, ready-to-throw rocks volcanoes. Which raises the obvious question of why the islands’ sleeping volcanoes can be tapped so effectively.

Finding out answers raises a couple more general questions: what does it take to have a good geothermal energy supply, and is tapping it really as simple as sticking a pipe in the ground?