Geol225

the process of breaking down rocks and minerals

the disintergration of rocks and minerals by physical processes

the chemical alteration or decomposition of rocks and minerals

• -Frost wedging-water expands 9% and cracks rocks
• -Pressure Release with exfoliation-the exposed surface of a pluton cracks as pressure from surrounding country rocks is released (exfoliation or "shedding" of the exposed rock "skin" can occur.
• -thermal expansion and contraction- the volume of rocks changes as they heat up and cool down
• -salt weathering-salt solutions seep into cracks
• -plants-crush and dissolve rocks

Chemical weathering includes those processes by which rocks and minerals are decomposed by chemical alteration of the parent material it also changes the composition of weathered materials

• 1. dissolution-common in limestone (carbonic acid + limestone)
• 2. Hydrolysis-hydrogen ions actually replace positive ions in minerals
• -oxidation refers to reactions with oxygen to form an oxide or if water is present a hydroxide (Ex. rust forms when oxygen reacts with minerals which contain iron)

• 1. Climate-water and temp
• 2. Time- more time=more weathering
• 3. Organisms
• 4. Mineralogy-weathering resistance of different minerals

a mixture of weathered rock material, water, air, and organic matter

• O horizon-organic matter
• A horizon-top soil, intense biological activity
• B horizon-subsoil, zone of accumulation
• C horizon-little organic matter, partially altered parent rock

• 1.Pedalfers: lot of rain, lot of organics in A horizon
• 2.Pedocals: not much rain, not much organics in A, stuff
• leached out of A forms nodules called caliche in B.
• 3.Laterites: Too much rain, little organics in A (all leached
• out), lots of clay in B.

• Pedalfers: eastern half of US
• Pedocals: western half of US
• Laterites: tropics

soil is required for agriculture

• Slash and burn, erosion by agriculture, salinization,
• pollution