under topsoil we find all kinds of things: animals and worms, old flower bulbs that might return, metal things that people up top are constantly trying to track down with detectors, dead people, good soil and bad soil, tunnels, underground chambers.
this is where things decompose and disappear. sometimes things take root and grow, maybe they take cover for a season and then return in a year, two years. this is where things go to get lost. the mantle is a quiet place, muffled in thick soil insulation, busy with composting and burrowing. a damp humid place with a high death/life turnover rate.
nothing can stay in an underground chamber forever. excavation pulls up all manner of STUFF. animals move their treasures to and fro. flowers beget more flowers. we even rob graves. eventually every last root is shaken free by an earthquake of great magnitude or a heavy flood.
i love that something is always happening under the surface, even something as simple as rest.