Forces that shape our earth

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Forces that shape our earth

  1. 1. Forces That Shape Our Earth: Weathering And Erosion
  2. 2. Weathering & Erosion: Erosion and weathering are major forces that shape Earth’s surface. For example, the Grand Canyon was formed through erosion by the Colorado River running through it!
  3. 3. What is weathering?Weathering: The breaking down of rocks into smaller pieces.1. Mechanical /Physical2. Chemical Hulk Rock Smash!
  4. 4. So what is erosion?Erosion: The movement of weathered rock by wind, water, glaciers & gravity
  5. 5. Types of Weathering:Mechanical/Physical: Rock is physically broken into smaller pieces (larger pieces become smaller pieces of the same rock)Chemical: Rock is chemically changed (like rusting or dissolving away)
  6. 6. 5 Agents of Mechanical Weathering:1. Release of Pressure2. Freezing & Thawing3. Animal Actions4. Plant Growth5. Abrasion
  7. 7. Release of Pressure As the surface of a rock is eroded, the rock begins to release pressure Causes top layers of the rock to crack and flake off
  8. 8. Release of pressure: rock cracks like an egg shell
  9. 9. Freezing & ThawingWhen water in the cracks of rocks freezes it expands causing the crack to enlarge or get bigger. The ice melts & refreezes over & over, breaking the rock apart.
  10. 10. Result of Freezing & Thawing
  11. 11. Animal ActionsAnimals dig (burrow) through the ground to make their homes. This loosens the soil & breaks apart rocks.
  12. 12. Plant Root GrowthPlants roots can grow into cracks in the rock, slowly breaking them apart.
  13. 13. Abrasion Sand and other rock particles in wind, water or ice can wear away exposed rock surfaces. Like sandblasting or sandpaper on wood
  14. 14. Chemical WeatheringThe process that breaks down the surface of rock by chemical changes.
  15. 15. 5 Agents of Chemical Weathering1. Water2. Oxygen3. Carbon Dioxide4. Living Organisms5. Acid Rain
  16. 16. WaterWater dissolves rockWater is the most important cause of chemical weathering
  17. 17. Oxygen Oxygen + Water + Iron = Rust through the Chemical reaction called Oxidation Rock will become crumbly, soft, and appear reddish-brown in color
  18. 18. Rusted rock on hillside
  19. 19. Carbon DioxideCO2 + rainwater = Carbonic AcidCarbonic Acid weathers softer rock like limestone & marble as it seeps into spaces in rock.Ex: sinkholes, caves
  20. 20. Living OrganismsThe roots of plants make a weak acid that slowly dissolves rocks around the plant.
  21. 21. Lichens grow on rock
  22. 22. Acid RainAcid rain causes rocks to weather very rapidly.

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