Weathering and erosion - PowerPoint PPT Presentation

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Weathering and erosion

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  1. Weathering and erosion November 5, 2013

  2. Why are roads in the south better than roads in the north? • Roads are like huge rocks and are subject to weathering which is the breakdown of rock materials by the action of physical and mechanical processes • Why do rocks weather? • Differences between conditions deep inside the earth and conditions at the surface • 2 types

  3. Mechanical weathering • Breakdown of rock into smaller pieces without changing the make-up of the rock. • Still the same kind of rock only smaller 3 ways this can take place: 1. Ice wedging – occurs when water goes into the cracks of rocks and freezes. As water freezes it expands and causes the rock to split apart ex. Jagged mountain top rocks

  4. 2. Wetting and drying – water seeps into rock and causes it to swell and when it dries out it breaks off.

  5. 3. Plants, animals, and humans (PAH)– plants grow roots into rocks breaking them apart. • Animals walk over rocks breaking them apart

  6. Chemicalweathering • Breaks down rocks by changing the composition of the rocks • 3 kinds: • 1. Hydrolysis – water reacts with rock to make a new type of rock

  7. 2. Oxidation – occurs when oxygen reacts with rock and makes a new kind of rock • Ex. Rusting (why our soil is red)

  8. 3. Carbon dioxide – dissolves easily in water to make carbonic acid • Ex, Acid rain (why monuments don’t last forever)

  9. What affects the rate at which rocks weather? • 1. Amount of surface area – the more area, the faster they weather • 2. Type of rock – less resistant slate weathers faster than granite • 3. Climate – warm wet conditions weather by chemical means, cool dry conditions weather by mechanical means