[pixl97]

If the Earth didn't have a huge internal geological reserve of hydrogen (and other gaseous chemicals) we'd effectively be a dead planet. It's easy to lose hydrogen to space, which is one reason we don't see much of it in the atmosphere. When we start talking about geologic timescales it would lead to the disassociation and lose of almost all atmospheric gasses. Luckily we have the tectonic plate cycle that puts new gasses in the atmosphere and kicks our eventual extinction down the road a bit farther. This also leads to earth shrinking over these very long time periods.