Two main types of weathering: Mechanical and Chemical
I. Mechanical Weathering—breaking rock into smaller pieces by physical means
2. Plants and Animals
4. Running water
Overlying rocks are eroded, buried granite rises to surface and erodes, decreases pressure on it, joints develop, breaks into sheets and peels away—exfoliation.
A. Ice Wedging—freezing and thawing of water in rock cracks widens and deepens the cracks
B. Abrasion—collision and grinding of rocks resulting in breaking and wearing away
2. Running water
C. Plant and Animal Activity
1. Roots grow and expand, create pressure and wedge rock apart. Larger plant roots get it and make cracks larger
2. Animals move soil and expose more rock—ants, squirrels, worms, coyotes, rabbits,
II. Chemical Weathering—chemical reactions act on minerals in the rock
A. Oxidation—elements combine with oxygen (Iron and oxygen combines to rust).
1. Feldspar and water combine to form clay
2. Leaching—minerals dissolve in water and are then carried to lower layers of rock.
C. Carbonation—CO2 in air dissolves in water, forms carbonic acid which then combine with minerals to form carbonates and react with limestone
D. Organic Acids—produced by lichens and moss growing on rock, seep into cracks and break apart