Download Weathering Notes I. Weathering A. Weathering is a slow, continuous

Weathering Notes
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II.
III.
Weathering
A. Weathering is a slow, continuous process that affects all substances exposed to the
atmosphere.
B. Evidence of weather
a. Rust, peeling paint, fading colors, cracks in buildings
b. Piles of broken rock at the base of a cliff (talus)
Mechanical weathering
A. Rocks are broken into different shapes and smaller pieces.
B. Examples
a. Temperature changes (hot or cold)
i. Results in cracks, flakes or exfoliation (sheets)
b. Frost action
i. Water gets into cracks and freezes, expanding the size of the crack
c. Organic activity
i. Root pry by growing roots
ii. Animal activity
d. Gravity
i. Falling rocks may break
e. Abrasion
i. Wearing away material by particles carried by wind, water or ice
Chemical weathering
A. Changes occur in the mineral composition (chemical) of rocks
a. Decomposition
i. Minerals are broken down into other substances
b. Water
i. Most chemical weathering is caused by water
ii. Rocks that dissolve are soluable
c. Oxidation
i. Process in which oxygen combines with another substance
ii. Example—rust
d. Carbonation
i. When carbonic acid (water + soil) reacts with another substance
(calcium or limestone)
ii. Results can be caves or sinkholes
e. Sulfuric acid
i. Sulfur dioxide combines with moisture in the air to form an acid
ii. Results can be the dissolving of materials
iii. Common source is volcanic gases
f. Plant acids
i. Plant produce acids that may dissolve rocks
IV.
ii. Root tips produce this acid
iii. Lichen produces this acid
Rates of weathering
A. The rate of weathering depends on 5 factors
a. Mineral composition of rocks
b. Climate
c. Time
d. Air pollution
e. Amount of exposed surface