Regolith

Regolith is a layer of loose, heterogeneous material covering solid rock. Regolith is present on Earth, the Moon, some asteroids, and other planets. The causes of regolith on earth are weathering and biological processes. On bodies without an atmosphere, regolith is caused by the gravitational reaggregation of debris resulting from impact with other objects.

On Earth, it is one of the important factors for most life, since few plants can grow on or within solid rock, and animals would be unable to burrow or build shelter without a loose material.