1. Weathering

2. Process by which rocks are broken down physically or chemically
Weathering
Process by which rocks are broken down physically or chemically

3. Mechanical Weathering
Rock is physically (something hitting it) broken down into smaller pieces.

4. Mechanical Weathering

5. Mechanical Weathering
What are the agents (causes) of mechanical weathering?

6. Causes of Mechanical Weathering
Ice (ice wedging-the freezing and thawing of water breaks a rock
Wind (wind blows sand against rock and it breaks down)
Water (water moves rock against other rocks and they break - river rocks)
Gravity (gravity moves rock down a hill and it breaks rocks)
Plants and Animals (plant roots or animals burrowing)
Abrasion - the grinding of rock by other rock carried by wind, water, & gravity.

7. Rock breaks down through chemical reactions.
Chemical Weathering
Rock breaks down through chemical reactions.

8. Chemical Weathering

9. What are the agents (causes) of chemical weathering?

10. Agents of Chemical Weathering (Weak Acids)
Water (dissolves rock over LONG periods of time)
Acid Precipitation (rain, snow, sleet, or hail with acid from fossil fuels)
Acids in Groundwater (karst features such as caverns; carbonic acid in caves)
Acids in Living Things (lichens produce acids)
Air (oxygen reacts with iron in rocks to create rust – oxidation)

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21. Mechanical AND Chemical Weathering http://humanities. cqu. edu
Mechanical Weathering (ice)
Mechanical Weathering (Wind by abrasion)
Chemical AND Mechanical Weathering (plant acid and plant roots)
Mechanical Weathering (wind and abrasion)

22. 6. Chemical Weathering (acid precipitation) http://marlimillerphoto
6. Chemical Weathering (acid precipitation) 7. Chemical Weathering (acid precipitation) 8. Chemical Weathering (water dissolves limestone)

23. 9. Chemical Weathering (lichens) http://www. cartage. org
10. Chemical Weathering AND Mechanical Weathering (wind and oxidation – rust)

24. What affects the rate rock weathers?
Type of Rock
Mineral composition – some minerals dissolve faster than others.
Permeable rock weathers easily because made of small air pockets.
Climate (average weather condition)
Wet, high climates = faster weathering
Dry, cool climates = slower weathering