Weathering
Physical and Chemical
Weathering
• The breaking down and changing of rocks
Weathering
• The breaking down and changing of rocks
• Two types:
– Mechanical
Weathering
• The breaking down and changing of rocks
• Two types:
– Mechanical
– Chemical
Mechanical Weathering
• Physical forces break rock
Mechanical Weathering
• Physical forces break rock
– Increases surface area
Mechanical Weathering
• 3 types:
– Frost wedging
Mechanical Weathering
• 3 types:
– Frost wedging
– Unloading
Mechanical Weathering
• 3 types:
– Frost wedging
– Unloading
– Biological activity
Frost Wedging
• When water freezes and thaws, it breaks rocks
open
Unloading
• As rock is uplifted and eroded, layers of rock
may peel off (exfoliation)
Biological Activity
• Weathering caused by living things
– Examples:
• Plant roots breaking rocks
• Animals burrowing
• Deforestation
Chemical Weathering
• Transformation of rock into one or more new
compounds
Agents of Chemical Weathering
• Water absorbs gases:
– Water + oxygen - causes oxides to form (oxidation)
Agents of Chemical Weathering
• Hydrolysis
– Feldspar to Clay
Agents of Chemical Weathering
• Water absorbs gases:
– Water + oxygen - causes oxides to form (oxidation)
– Water + carbon dioxide - forms carbonic acid
Agents of Chemical Weathering
• Water absorbs gases:
– Water + oxygen - causes oxides to form (oxidation)
– Water + carbon dioxide - forms carbonic acid
– Water + sulfur oxides, nitrogen oxides – acid rain
Rate of Weathering
• Mechanical weathering accelerates chemical
weathering
Rate of Weathering
• Mechanical weathering accelerates chemical
weathering
• Also affected by:
– Rock characteristics (composition)
Rate of Weathering
• Mechanical weathering accelerates chemical
weathering
• Also affected by:
– Rock characteristics (composition)
– Climate (strongest in hot, humid areas)