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Wind and Wave Erosion

Wind and Wave Erosion. …and a teeny little bit about mass movement. What is EROSION?. The removal and transport of materials by natural agents such as wind , water and ice. WIND EROSION. Sediment Sizes. Sand A sediment size…not a composition 2mm  0.06mm Gritty feel

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Wind and Wave Erosion

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  1. Wind and Wave Erosion …and a teeny little bit about mass movement

  2. What is EROSION? The removal and transport of materials by natural agents such as wind, water and ice.

  3. WIND EROSION

  4. Sediment Sizes • Sand • A sediment size…not a composition • 2mm  0.06mm • Gritty feel • Can be composed of anything! • Not very cohesive

  5. Sediment Sizes • Silt • Smaller than sand • 0.06 mm  0.003mm • Fine like powder

  6. Sediment Sizes • Clay • < 0.003 mm • Smallest sediment size • Very cohesive

  7. Wind Erosion Deflation • Most common form of wind erosion • The removal and transport of silt

  8. Dust Bowl

  9. Kansas (1996)

  10. Deflation and desert pavement During this process wind removes the top layer of fine, dry rock/soil fragments too large for the wind to carry are left behind These remaining fragments form a surface of closely packed rocks called desert pavement.

  11. Wind Erosion • Saltation- bouncing of sand grains (wind lifting then dropping) http://www.nps.gov/grsa/resources/saltation.htm

  12. WAVE EROSION

  13. What causes waves?

  14. Why do waves “break”? • Waves approach shoreline smoothly until they reach shallow water. • As waves scrapes the bottom, the lower part slows down and the upper part moves ahead… • The crest falls over and breaks onto the surf

  15. Longshore drift • Water and sediment are transported in a zig-zag pattern as longshore currents and waves approach the shoreline at an angle. • This zig-zag pattern is the mechanism for sediment transport as the swash is immediately followed by the backwash to the ocean. • This energy created from the breaking waves allows for weak currents to carry large amounts of coarse-grained sediment down the shoreline.

  16. Current + wave motion= longshore drift

  17. Another look at it…

  18. One more look…

  19. Carefully examine the photo. Which direction is the long shore current coming from?

  20. Answer: West Longshore current

  21. Mass Movement (aka Mass Wasting) mudslide landslide creep rockfall slump creep

  22. What is MASS MOVEMENT? The term refers to downward transportation of weathered materials by gravity

  23. Triggers of Mass Movements • Heavy rain • Spring Thaws • Volcanic Eruptions • Earthquakes • MOST COMMON?...heavy rains

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