Weathering refers to the various mechanical and chemical processes that cause exposed rock to decompose. Weathering involves two processes:
- chemical weathering and
- mechanical weathering
Both processes occur in place. No movement is involved in weathering.
Chemical weathering involves a chemical change in at least some of the minerals within a rock.
Mechanical weathering involves physically breaking rocks into fragments without changing the chemical make-up of the minerals within it.
As soon as a rock particle (loosened by one of the two weathering processes) moves, we call it erosion. We call it erosion if the rock particle is moved by some flowing agent such as air, water or ice.