Weathering Physical/ Mechanical Weathering

1. Weathering & Erosion The breakdown of the materials of Earth’s crust into smaller pieces. Process by which rocks are broken down into smaller pieces by external conditions (wind, water, ice…) Weathering Physical/Mechanical Weathering

2. 5 Types of Physical weathering • Frost heaving/wedging: water in cracks, freezes, & expands • Plant roots: grow in cracks causing the rock to break • Friction & impact: rocks breaking rocks • Burrowing of animals • Unloading: overlying rock eroded away creates exfoliation domes.

3. Chemical Weathering The 5 agents of chemical weathering The process that breaks down rock through chemical changes. • Water weathers rock by dissolving it • Oxygen combines with iron and forms rust • Carbon dioxide dissolves in rain water and creates carbonic acid • Carbonic acid easily weathers limestone and marble

4. Living organisms • Lichens that grow on rocks produce weak acids that chemically weather rock • Acid rain • Compounds from burning coal, oil and gasoline react chemically with water forming acids in the clouds and are released when it rains • Acid rain causes very rapid chemical weathering

5. Factors that affect weathering • Climate: Warm and wet • Surface area • Chemical composition of rock

6. Erosion 4 Types of Erosion The process by which water, ice, wind or gravity moves fragments of rock and soil. • Water: Rivers, streams, and runoff move soils, rocks and sediments around • Glaciers moving across the landscape • rocks & boulder moved from place to place • the glaciers carve into the land

7. Wind removing the different surfaces from one place and depositing it in another • Mass Movement of Land • Landslides • Mudslides • Slump: when part of a hill moves a short distance down a hill) • Creep: slow movement of land down a slope

8. Which rock layer appears to be the least resistant (weakest)? • Which rock layer appears to be the most resistant (strongest)? • Resistant rocks usually form steep cliffs and waterfalls, by sticking out further than the lower layers)?

9. Deposition • the process whereby these sediments are released by their transporting agents (dropped). Most deposition happens in standing/still bodies of water (oceans/lakes). • Deposition is caused by the slowing down (loss of kinetic energy) of the agent of erosion.

10. Delta – a fan shaped deposit that forms at the mouth of a river/stream when it enters a larger body of water. This is seen under the water. The particles are horizontally sorted.