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Wave Erosion and Marine Geology

Wave Erosion and Marine Geology . Take-Away Points. Waves are created by the wind Water in a wave oscillates but does not move with the wave What happens when waves hit the shore Storm surges can be catastrophic How coastlines evolve

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Wave Erosion and Marine Geology

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  1. Wave Erosion and Marine Geology

  2. Take-Away Points • Waves are created by the wind • Water in a wave oscillates but does not move with the wave • What happens when waves hit the shore • Storm surges can be catastrophic • How coastlines evolve • Deltas are influenced by deposition, tides, and wave action • Reefs are important coastlines in tropical regions • Submarine landslides

  3. Wave Motions • Particles in a wave travel circular paths • The water in a deep-water wave does not move forward • Below wave base, wave effects are negligible 1. Waves are created by the wind

  4. Wave Motions 2. Water in a wave oscillates but does not move with the wave

  5. The Highest Recorded Ocean Wave 2. Water in a wave oscillates but does not move with the wave

  6. Freak Waves • Addition of waves of different frequencies • Theoretically could reach 200 feet in Gulf of Alaska • One nearly sank the Queen Mary in WWII, with 15,000 troops aboard.

  7. When Waves Meet the Shore When the bottom interferes with wave motion, the wave steepens and the top overtakes the bottom. 3. What happens when waves hit the shore

  8. Wave Refraction • Waves change path when they reach shallow water • Wave energy is concentrated on headlands and spread out in bays 3. What happens when waves hit the shore

  9. Rips • When waves break parallel to a beach, rips occur 3. What happens when waves hit the shore

  10. Storm Waves: Galveston, Texas, September 8, 1900: • 6000-8000 dead • 3600 houses destroyed 4. Storm surges can be catastrophic

  11. Raising Galveston – 6 in. to 17 ft.

  12. “A rickety maze such as Dr. Seuss might have drawn”

  13. The Lift in Progress

  14. Pumping in the Sand 4. Storm surges can be catastrophic

  15. The Galveston Seawall 4. Storm surges can be catastrophic

  16. In the long run, nothing is as futile as trying to resist shoreline change. Change can be resisted for a while, but when the water wants something badly enough, it will come in and take it. 5. How Coastlines Evolve

  17. Property Values and Shoreline Erosion • If more than half the original lot is left, it’s Location, Location, Location • After that, it becomes obvious there soon won’t be any location left 5. How Coastlines Evolve

  18. Marine Erosion • Chemical Attack • Abrasion • Wave Impact • Compressed Air • Backwash 5. How Coastlines Evolve

  19. Longshore and Beach Drift • Most Beach Sand Is Created by Weathering and Carried to Coasts by Rivers • Beach Sand Moves along the Coast by Longshore and Beach Drift 5. How Coastlines Evolve

  20. Longshore Drift 5. How Coastlines Evolve

  21. Types of Coast Degree of Modification • Primary - Not Modified Much by Wave Action • Secondary - Highly Modified by Wave Action History • Emergent - Land Rises or Water Level Falls • Submergent - Land Sinks or Water Level Rises Dominant Process • Erosional • Depositional 5. How Coastlines Evolve

  22. Effects of the Pleistocene • Sea level has risen at least 100 meters in the last 18,000 years • Most coastlines globally are submergent • Primary coastlines are very common 5. How Coastlines Evolve

  23. Secondary Coasts Are Modified by Marine Erosion or Deposition 5. How Coastlines Evolve

  24. Secondary Coasts Erosion • Stack • Terraces • Erosion rate becomes very slow • wave energy dissipated crossing the wave-cut terrace. • Cliffs become higher, meaning more material to move. Deposition • Spit • Lagoon • Baymouth Bar • Barrier Bar 5. How Coastlines Evolve

  25. Primary Coastlines Are Very Common • Drowned River Valleys (Estuaries) • Drowned Glacial Valleys (Fiords) 5. How Coastlines Evolve

  26. Other Ways Primary Coasts Can Form • Deltas • Volcanic Activity • Uplift 5. How Coastlines Evolve

  27. Primary and Secondary Coastlines 5. How Coastlines Evolve

  28. Delta Coasts • Deposition-Dominated • Wave Dominated • Tide-Dominated 6. Deltas are influenced by deposition, tides, and wave action

  29. The Mississippi – A Deposition-Dominated Delta 6. Deltas are influenced by deposition, tides, and wave action

  30. Yukon and Nile Deltas – Balance of Deposition and Wave Action 6. Deltas are influenced by deposition, tides, and wave action

  31. Sao Francisco, Brazil – A Wave-Dominated Delta

  32. Ganges, Bangladesh – A Tide-Dominated Delta

  33. Reefs Are a Major Type of Coast in Tropical Areas 7. Reefs are important coastlines in tropical regions

  34. Tarawa – A Typical Atoll 6. Reefs are important coastlines in tropical regions

  35. Reefs Also Form along the Edges of Large Islands and Continents These Are Barrier Reefs • Australia • Yucatan • Belize • West Florida 6. Reefs are important coastlines in tropical regions

  36. Turbidity Flows – Grand Banks, 1929 8. Submarine Landslides

  37. Take-Away Points • Waves are created by the wind • Water in a wave oscillates but does not move with the wave • What happens when waves hit the shore • Storm surges can be catastrophic • How coastlines evolve • Deltas are influenced by deposition, tides, and wave action • Reefs are important coastlines in tropical regions • Submarine landslides

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