Why will a radioactive rock never become completely stable?

Technically speaking, depending on the sample, the rock could become “stable.”

The radioactive decay of a radioisotope is expressed as a half-life equation; half-life is the colloquial term that describes how long it will take for half of the radioisotope to decay into another isotope or element. For example (if I remember correctly), Carbon-14 has a half life of 5,780 years. This means that in a 100% sample of C-14, after 5780 years passes, only 50% of that isotope would remain; another 5780 years, and only 25% would remain (half of half). Based on this principle, it seems like a sample could never fully decay because there’s always an amount that smaller than the current amount.

However, if the sample has a very short half life (milliseconds or nanoseconds) the sample would reach nigh-full decay eventually. At this point, it is considered “stable.”

Wetlands form where water and land meet. a lake with a wetland fringe can fill in with decayed plant and animal material to become a wet meadow. a pond can fill in to become a bog or fen. sediment can fill in a river marsh to become a swamp.flooding of coastal lowlands from rising sea levels has created broad coastal marshes that are protected from wave action by barrier islands or reefs. coastal wetlands also form when rivers deposit sediment as they reach the ocean. plants then take root and hold the soil firm against the forces of tides and waves.