Natural Process of Smoothing or Wearing Away

This page is the CodyCross answer for the clue below from Tracking Time, Group 1044, Puzzle 3 (Before and After).

Question is: Natural Process of Smoothing or Wearing Away

and the answer is: EROSION

Word Meaning:

EROSION — (chiefly uncountable) The result of having been worn away or eroded, as by a glacier on rock or the sea on a cliff face.

Definitions from Wiktionary.