heftig

Well, Wikipedia claims

The Earth has an internal heat content of 10³¹ joules (3×10¹⁵ TWh), About 20% of this is residual heat from planetary accretion; the remainder is attributed to past and current radioactive decay of naturally occurring isotopes.

In that sense, it’s the only renewable energy source we have that’s not indirectly powered by the sun. It’s most similar to (proper) nuclear power, but the latter isn’t “renewable” because it requires digging up fuel from the crust.

Isn’t geothermal mostly nuclear power?

They’re usually also Biblical literalists, who believe that their infallible God-authored Bible says the Earth is flat (“four corners”, covered in a dome, etc), thus the globe is an attack on Christianity. The worldly institutions are all controlled by the devil, who wants Christians to doubt their Bible and their belief in God.

https://youtu.be/JTfhYyTuT44