Weathering

The Chemical and physical breakdown of material (rock).

Disintegration The breaking up of material into smaller pieces Also called Physical or Mechanical Weathering –Thermal Expansion –Frost Wedging –Plant and Animal Action –Unloading

Thermal Expansion Material expands when it gets warmer. The outside of a rock will get hotter than the inside during the day and colder at night, therefore the outer part expands and contracts more than the inner part. Exfoliation

Thermal Expansion Examples: –Expansion Joints on bridges. –Ice crackling in water –Hot water on cold glass –Cold water on hot glass

Frost Wedging

Frost or Ice Wedging What conditions would cause a lot of ice wedging?

How potholes form

Plant and Animal Action

Plant Roots

Root damage to sewer lines

Unloading & Jointing

Jointing

Decomposition The chemical changing of material into a new material. Most important agent involved is water. Also called Chemical Weathering –Acids –Hydrolysis –Oxidation

Acids Carbonic Acid or Carbonation H 2 O + CO 2 + CaCO 3 --> Ca +2 + HCO 3 -

Acids Organic Acids –Lichens –Plants –Animals Sweat Urine

Hydrolysis and Hydration Reacting with water –KAlSi 3 O 8 + H > Al 2 Si 2 O 5 (OH) 4 + SiO 2 + K(OH)

Oxidation Rust Fe +2 +O 2 --> Fe 2 O 3

Chemical helps Physical by making the rock weaker

Physical helps Chemical by increasing the surface area

Differential Weathering

Factors that Influence the Rate of Weathering

Rates of Weathering Rates of Weathering of Clean Rock Surfaces (micro-meters/1000years) Rock TypeCold ClimateWarm, Humid Climate Basalt10100 Granite110 Marble20200

60 years of weathering

60 years of weathering and plant growth.

Effect of humid climate on Cleopatra’s Needle.

Weathering Mass Wasting Erosion

The Result of Weathering

The End