Transcript Weathering

Weathering
– The chemical and physical
breakdown of rocks.
 2 kinds of weathering:
 1. Physical (Mechanical) Weathering

- When rock is cracked, split or broken
into smaller pieces called sediments.

a) Ice Wedging – breaking down by
freezing and thawing
 Weathering
Ice Wedging or Frost Wedging
b) Abrasion – wearing down by rubbing
or bouncing along other surfaces.

c) Exfoliation – peeling away of large
sheets of material at the rock’s surface.

d) Biological Processes – plant roots
and animal digging breaks down rock

Chemical Weathering – actually
changes the chemical composition of the
rock (dissolving or adding oxygen)
 2.
Abrasion and Exfoliation
Biological Processes
a) 0xidation – when oxygen combines
with minerals in a rock.

Oxygen + iron = rust
 b) Hydration – when water combines with
minerals to dissolve them.
 c) Carbonation – when CO2 combines
with minerals.

CO2 + H2O = Carbonic Acid

- Carbonic Acid dissolves limestone to
form underground caverns.

Rust (oxidation)
Cavern Formation
Luray Caverns VA - Carbonation
Rates of Weathering
 Factors
affecting rate (how fast)
weathering occurs

1. Surface Area – the more surface
exposed to the air and water, the faster the
weathering.

- A large rock will weather faster if it is
broken up into small pieces.
2. Mineral composition (hardness) –
rocks made from harder, more resistant
minerals weather more slowly.
 3. Climate –

Fast Weathering
 Wet/Humid
 Cold/warm alternating
Slow Weathering
 Dry

Cleopatra’s Needle