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Warm-Up

Warm-Up. How would you describe the difference between a new tombstone and one that is 100 years old?. Rocks & Weathering. The Effects of Weathering. Weathering is the process that breaks down rocks and other substances at Earth’s surface. Sierra Nevada Mtns. ~20 myo.

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Warm-Up

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  1. Warm-Up How would you describe the difference between a new tombstone and one that is 100 years old?

  2. Rocks & Weathering

  3. The Effects of Weathering • Weathering is the process that breaks down rocks and other substances at Earth’s surface Sierra Nevada Mtns. ~20 myo Appalachian Mtns. ~250 myo

  4. Two Types of Weathering • Mechanical (physical) • Chemical

  5. Two Types of Weathering • MechanicalWeathering • (also called physical weathering) • rock is physically broken into smaller pieces without changing what the rock is composed of

  6. Two Types of Weathering • Mechanical Weathering • (also called physical weathering) • rock is physically broken into smaller pieces without changing what the rock is made of Examples: • Abrasion—grinding away of rock by other rock particles carried by water, ice, wind, or gravity

  7. Two Types of Weathering • Mechanical Weathering • (also called physical weathering) • rock is physically broken into smaller pieces without changing what the rock is made of Examples: • Ice wedging—water freezes and expands, acting like a wedge that pushes open cracks in rocks

  8. Two Types of Weathering • Mechanical Weathering • (also called physical weathering) • rock is physically broken into smaller pieces without changing what the rock is made of Examples: • Exfoliation—layers of rock crack and flake off when pressure is removed from the rock

  9. Two Types of Weathering • Mechanical Weathering • (also called physical weathering) • rock is physically broken into smaller pieces without changing what the rock is made of Examples: • Plant growth—roots grow into cracks in rocks and pry cracks farther apart

  10. Two Types of Weathering • Mechanical Weathering • (also called physical weathering) • rock is physically broken into smaller pieces without changing what the rock is made of Examples: • Animal action—animal burrowing breaks apart rocks in the soil

  11. Two Types of Weathering • ChemicalWeathering • rocks are made of minerals • rock is broken down by chemically changing the minerals that makes up the rock into new minerals

  12. Two Types of Weathering • ChemicalWeathering • rocks are made of minerals • rock is broken down by chemically changing the minerals that makes up the rock into new minerals Examples: • Water—water dissolves minerals in some rocks

  13. Two Types of Weathering • ChemicalWeathering • rocks are made of minerals • rock is broken down by chemically changing the minerals that makes up the rock into new minerals Examples: • Oxidation—oxygen reacts with minerals (iron) in some rocks (“rusting”)

  14. Two Types of Weathering • ChemicalWeathering • rocks are made of minerals • rock is broken down by chemically changing the minerals that makes up the rock into new minerals Examples: • Carbonic acid—carbon dioxide and water form carbonic acid which reacts with minerals (marble & limestone) in some rocks

  15. Two Types of Weathering • ChemicalWeathering • rocks are made of minerals • rock is broken down by chemically changing the minerals that makes up the rock into new minerals Examples: • Living organisms— plant roots & lichens (plant-like organisms) produce weak acids that can dissolve some minerals in rocks

  16. Two Types of Weathering • ChemicalWeathering • rocks are made of minerals • rock is broken down by chemically changing the minerals that makes up the rock into new minerals Examples: • Acid Rain—burning fossil fuels releases chemicals into the air that react with water to form acids which can dissolve rocks

  17. Rate of Weathering • How fast rocks are broken down depends on: -Type of rock -Climate

  18. Rate of Weathering • How fast rocks are broken down depends on: -Type of rock • some rocks are made of minerals that dissolve easier Example: limestone contains calcium that dissolves easily

  19. Rate of Weathering • How fast rocks are broken down depends on: -Type of rock • some types of rock are permeable (they contain tiny holes that absorb water), so they weather faster Example: marble is more permeable than slate Slate 1856 Marble 1897

  20. Rate of Weathering Egypt ~4500 yo • How fast rocks are broken down depends on: -Climate • Mechanical & chemical weathering occur faster in places that are wet (have more rain) Example: pyramids in Egypt have weathered slowly because of dryness of desert Mexico ~1800 yo

  21. Rate of Weathering Connecticut • How fast rocks are broken down depends on: -Climate • chemical weathering occurs faster in places that are hot Example: granite weathers ten times faster in hot climates than cold Mojave Desert

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