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Waves and Coasts

Waves and Coasts. waves. Agents of erosion as get closer to shore: wavelength decreases velocity decreases amplitude increases in shallow water, waves BREAK. Breaking waves scoop out a TROUGH and deposit a BAR.

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Waves and Coasts

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  1. Waves and Coasts

  2. waves • Agents of erosion • as get closer to shore: • wavelength decreases • velocity decreases • amplitude increases • in shallow water, waves BREAK

  3. Breaking waves scoop out a TROUGH and deposit a BAR

  4. Turbulent water from breaker rushes up beach (SWASH) and then flows back (BACKWASH) • waves come in to the shore at an angle (REFRACTION)

  5. Consequence of wave refraction • Littoral Drift • Beach drift: movement of sand particles down the beach by swash and backwash • Longshore drift: movement of particle just offshore by the longshore current (parallel to beach)

  6. Landforms resulting from littoral drift: 1. Spit (e.g., Park Point)

  7. Landforms resulting from littoral drift: 2. baymouth bar and lagoon

  8. Landforms resulting from littoral drift: 3. tombolo

  9. Stockton Island, Apostle Islands

  10. On an embayed coast, • Wave energy converges on HEADLANDS, and therefore erosion is concentrated there: CLIFFS • BAYS receive less energy, less erosion,and therefore deposition of sand occurs there: BEACHES

  11. landforms on the headlands: 1. Wave-cut abrasion platforms: • sloping rock surfaces abraded by waves beneath breakers

  12. landforms on the headlands: 2. Wave-cut notches

  13. landforms on the headlands: 3. Sea stacks and sea arches

  14. Where does beach sand come from? • Erosion of headlands • offshore material brought to shore • fluvial sediment

  15. Types of coastlines 1. Ria Coast: • coast that was formerly dissected by stream valleys; then sea level rose and inundated the valleys

  16. Types of coastlines 2. Fiord coast: • coast that was formerly dissected by glacial troughs; then sea level rose and they became inundated

  17. Types of coastlines 3. Barrier Island Coast: • sand bars (barrier islands) created by littoral drift, parallel shore, enclose lagoons

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