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Weathering, Erosion and Deposition.(3rd/4th grade teach)

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Weathering, Erosion and Deposition.(3rd/4th grade teach)

  1. 1. Weathering, Erosion and Deposition By Moira Whitehouse PhD
  2. 2. The Earth’s surface is constantly changing. Mount St Helens before and after it erupted in 1980.
  3. 3. New land is constantly being formed. Volcanoes erupt. Forces deep in the Earth push up chains of mountains.
  4. 4. Land is being constantly worn down by wind, water and ice. original level of the plateau.
  5. 5. Weathering • The breaking down of rock into smaller and smaller pieces.
  6. 6. Some things in nature that cause weathering Water in cracks in the rock freezing and expanding Plant roots growing into rocks Water running over rocks, causing the rocks to hit one another and break into smaller pieces Wind carrying sand that wears away rock Carbon dioxide dissolved in water forming an acid that eats holes in the rock
  7. 7. Water in cracks in the rock freezes. As it freezes it expands causing the rocks to break.
  8. 8. Expanding water as itwedgingslowly breaks up this Frost Action or ice freezes slowly breaks up this sedimentary rock into unusual shapes. rock into unusual shapes.
  9. 9. Plant roots break apart rocks
  10. 10. Weathering by running water When water in waterfalls, rivers and streams move over rock, the rocks are weathered—broken into smaller and smaller pieces.
  11. 11. Fast running water causes rocks to hit one another breaking them into smaller rocks.
  12. 12. Weathering by the wind As the wind blows it picks up small particles of sand and blasts large rocks with the abrasive particles, cutting and shaping the rock.
  13. 13. Blowing sand
  14. 14. Weathering by glaciers A glacier is a large, river of ice that moves very slowly downhill. Glaciers are formed over many years as large amounts of snow fall and accumulate. The snow compacts and changes to ice. Stuck in the bottom of the glacier are stones of various sizes that wear away the rock under the glacier as it moves downhill.
  15. 15. Striations or scratches made in the rock under a glacier by the stones stuck in it as the glacier moved downhill.
  16. 16. Carbon dioxide that dissolves in water weathers rock • CO2 dissolves in rain water and creates carbonic acid • Carbonic acid easily weathers limestone making holes in the rock
  17. 17. Erosion The process by which water, ice, wind or gravity moves pieces of rock and soil. When rock is weathered (broken into smaller and smaller pieces), these pieces are often carried away by water, wind or ice.
  18. 18. Water Erosion Rivers, streams, and runoff carry weathered rock or soil to another place.
  19. 19. Fast moving streams and rivers carry big and small rocks downstream.
  20. 20. Slower moving water carries smaller rocks and soil downstream.
  21. 21. Moving water can also cause soil erosion— carrying the soil away to a different location.
  22. 22. Sometimes a side of the hill is washed away by running water. The soil and rocks move down the hill in a landslide.
  23. 23. Canyons This simple animation provides you with a visualization of how the Colorado River has "downcut" into the rock layers of the Grand Canyon. Canyons demonstrate both weathering—the breaking down of rock into smaller pices and Canyons are large erosion—these pieces of rock valleys created by a being moved to a new location. river or stream.
  24. 24. Wind Erosion Strong winds can move small rocks and soil from one location to another.
  25. 25. Ice Erosion Glaciers moving over rocks breaks them down into smaller pieces (weathering) and carries them away (erosion).
  26. 26. Deposition When the water slows down or stops moving When the wind dies down or stops blowing When the glacier melts the rocks that the water, wind or glacier were carrying are dropped or deposited in a new location.
  27. 27. Delta—water deposition Where a river meets the ocean is called the mouth of the river. Soil carried by a river is deposited at the mouth and new land is formed. This new soil-rich land is known as a delta.
  28. 28. Wind Deposition Sand dunes are large deposits of sand dropped when the wind stopped blowing. The location of the sand dunes shifts frequently.
  29. 29. Glacial Deposition When glaciers melt, they drop or deposit the rocks they were carrying. A moraine is the rocks and soil left behind by a melting glacier. Glaciers pick up rocks and dirt that travel along with the glacier until it eventually melts and is left behind as till.
  30. 30. Although we talk about weathering, erosion and deposition as three separate processes, they often occur together. Over time, rocks are generally broken into smaller pieces (weathering) carried downhill (erosion) and deposited in a new location (deposition).
  31. 31. Do you remember the agents of weathering that we discussed? moving water in water in cracks in rocks streams and rivers freezing and expanding glaciers plant roots wind Do you remember the agents of erosion that we discussed? moving water in glaciers wind streams and rivers