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Rocks and Weathering

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  1. Rocks and Weathering Chapter 2 Section 2 6th Grade Team

  2. Standard • S 6.2.aStandard • S. 6.2 Topography is reshaped by the weathering of rock and soil and by the transportation and deposition of sediment. • S.6.2.a Students know water funning downhill is the dominant process in shaping the landscape, including California’s landscape.

  3. Anticipatory Set

  4. Vocabulary • Weathering • Erosion • Uniformitarianism- • Mechanical Weathering • Abrasion • Ice Wedging- • Chemical Weathering • Oxygen

  5. Weathering and Erosion (Input) • Weathering – the process that breaks down rock and other substances at Earth’s surface. (NTG) • Repeated freezing and thawing can crack rocks into small pieces. • You do not have to look at the mountains to see weathering. It occurs on your bike as they begin to rust, or the paint peels, sidewalks crack, and potholes form.

  6. Mechanical Weathering • Mechanical Weathering- in which rocks are physically broken into smaller pieces. • It acts slowly, but over time they break down even the biggest, hardest rocks. It can wear away whole mountains. • Abrasion- grinding away of rock by rock particles carried by water, ice, wind, or gravity.

  7. Types of Mechanical Weathering • Cool climates- freezing and thawing of water • Ice Wedging- • Release of Pressure • Freezing and Thawing • Animal Actions • Plant Growth • Abrasion

  8. Chemical Weathering • Water- water weathers rock by dissolving it. It mixes uniformly throughout the water to make a solution. • Oxygen- Iron combines with oxygen in the presences of water in a process called oxidation. (NTG). It produces rust. • Rust makes rock soft and crumbly and gives it a red or brown color. • Carbon Dioxide- it dissolves in rainwater and in water that sinks through air pockets in the soil. It creates a weak acid called carbonic acid.

  9. Chemical Weathering • Living Organisms- Plants root grow and produce weak acids that slowly dissolve rock around the root. Lichens (plantlike organisms on rocks) also produce weak acid. • Acid rain- Burning fuels such as coal, oil, and gas for energy can pollute the air with sulfur, carbon and nitrogen compounds. These compounds reach with water vapor in the clouds and produce acid rain. They mix with raindrops and fall as acid rain.

  10. Rate of Weathering • The most important facts that determine the rate at which weathering occurs are the type of rock and climate. • Type of Rock • The minerals that make up the rock determine how fast it weathers. • Permeable- that a materials is full of tiny, connected air spaces that allow water to seep through it. They will weather faster because water seeps into the air spaces and dissolves and removes material brown down by weathering.

  11. Checking for Understanding • What is weathering? • What is erosion? • What is Ice Wedging? • What grinds away rock by rock particles carried by wind, ice, water or gravity? • List the types of mechanical weathering

  12. Guided Practice Independent Practice • GP • NTG page 38-39 # 1-7 • IP • NTG page 40-41 #8-25