regolith

The layer of loose, unconsolidated material covering bedrock — soil, gravel, sand, dust, volcanic ash, glacial till, and anything else that sits on top of solid rock. Regolith is the blanket between the living world and the planet's bones. On Earth, regolith is mostly soil; on the Moon, it is pulverized rock created by billions of years of meteorite impacts. The word names the universal condition of surfaces — the soft over the hard, the broken over the whole.