Geology and National Parks
Geology, Minerals, Energy and Geophysics Science Center home
These pages are static and not updated. Information found here represents historical USGS work that is no longer supported.
What's the difference between weathering and erosion?
Weathering involves two processes that often work
in concert to decompose rocks. 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. It's important to keep in mind that weathering is a surface or near-surface
As you know, metamorphism also produces chemical
changes in rocks, but metamorphic chemical changes occur at depth where
either the temperature
and/or pressure are significantly higher than conditions
found on the Earth's surface.
As soon as a rock particle (loosened by one of the
two weathering processes) moves, we call it erosion or mass
wasting. Mass wasting is simply movement down
slope due to gravity. Rock falls, slumps, and debris flows are all
examples of mass wasting.
We call it erosion if the rock particle is moved
by some flowing agent such as air, water or ice.
So, here it is: if a particle is loosened, chemically
or mechanically, but stays put, call it weathering.
Once the particle starts moving, call it erosion.