It Could Be a Vast Source of Clean Energy, Buried Deep Underground - The New York Times

Natural hydrogen, also called white hydrogen because of its purity, could be a game changer, scientists say, because it is a potential source of clean energy continuously generated by the earth. Hydrogen reservoirs form when heated water meets iron-rich rocks. According to the U.S. Geological Survey, just a small fraction of these deposits could provide enough clean energy for hundreds of years....

https://www.nytimes.com/2023/12/04/business/energy-environment/clean-energy-hydrogen.html