The deeper you go underneath the Earth's surface, the hotter it gets.
This is true almost everywhere on the planet.
Sometimes that energy can burst out into the air via volcanoes,
or less dangerously, in hot springs and geysers.
where water has passed through hot rocks many kilometres underground and risen to the surface.
Geothermal energy is so reliable that in some places, such as Iceland and California,
they use the hot water and steam coming from below to make clean, carbon-free electricity.
Unfortunately, it takes a lot of luck to make this work.
You need the right kind of rocks, an intense heat and pressure,
and all of it at relatively shallow depths.
Very few places in the world have those.
And so today, geothermal energy provides less than 1% of the world's electricity.
It's always, therefore, been in the shadows compared to its clean energy cousins,
such as solar, wind or nuclear.
But that could soon be history.
A new suite of technologies is promising to finally allow the heat inside the Earth to become available almost anywhere on the Earth.
So, yeah, just watch your step.
Obviously, trips and hazards, things are overhead, but it's pretty safe right now.
That's Jack Norbeck at a site in the Utah desert.
He's the Chief Technology Officer at Furvo,