Water reacts with iron-rich rock at depth.
Faults carry hydrogen upward.
Porous rock holds it.
A tight cap keeps it in.
Most probable H₂ in place worldwide (wide uncertainty).
Ellis & Gelman, 2024 [1]Purity at Bourakébougou, Mali, producing since 2012.
Prinzhofer et al., 2018 [2]Potential production cost of geologic hydrogen.
Mathur, 2025 [3]To find the *clean* *hydrogen* the Earth already makes, and make it *a* *reliable* *energy* *source.*