weathering the chemical and physical breakdown of material (rock)
TRANSCRIPT
Weathering
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 ExpansionMaterial 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
•
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
H2O + CO2 + CaCO3 -->
Ca+2 + HCO3-
Acids• Organic Acids
– Lichens– Plants– Animals
• Sweat• Urine
Hydrolysis and Hydration• Reacting with water
– KAlSi3O8 + H20 --> Al2Si2O5(OH)4 + SiO2 + K(OH)
Oxidation
• Rust
Fe+2 +O2 --> Fe2O3
Chemical helps Physical by making the rock weaker
•
Physical helps Chemicalby increasing the surface area
DifferentialWeathering
Differential Weathering
•
Factors that Influence the Rate of Weathering
Rates of Weathering
Rates of Weathering of Clean Rock Surfaces (micro-meters/1000years)
Rock Type Cold Climate Warm, Humid Climate
Basalt 10 100
Granite 1 10
Marble 20 200
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