This phenomenon, which provides evidence for the big bang theory, is called

Explanation:

The earliest and most direct observational evidence of the validity of the theory are the expansion of the universe according to Hubble's law (as indicated by the redshifts of galaxies), discovery and measurement of the cosmic microwave background and the relative abundances of light elements produced by Big Bang ...

answer; gravity pulls glaciers down hill and as glaciers flow it pick up rocks and soil;