Wave Erosion and Marine Geology

1. Wave Erosion and Marine Geology How waves behave How the sea modifies coastlines

2. Waves

3. Essential Points • Waves are created by the wind • Water in waves oscillates but does not move with the wave • What happens when waves hit the shore • Storm surges can be catastrophic How Waves Behave

4. Wave Fetch

5. Wave Fetch

6. The Highest Recorded Ocean Wave Waves are created by the wind

7. Global Wave Heights 1. Waves are created by the wind

8. 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. 1. Waves are created by the wind

9. 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 2. Water in a wave oscillates but does not move with the wave

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

11. 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

12. 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

13. Wave Refraction off Cape Cod 3. What happens when waves hit the shore

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

15. Rips, Lake Superior

16. Oblique Rips 3. What happens when waves hit the shore

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

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

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

20. The Lift in Progress

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

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

23. Essential Points • Waves are created by the wind • Water in waves oscillates but does not move with the wave • What happens when waves hit the shore • Storm surges can be catastrophic How Waves Behave

24. How the sea modifies coastlines

25. Essential Points • Wave Action erodes or deposits material along coastlines • Types of coastline • Deltas are governed by deposition, waves, and tides • Reefs are a special type of coastline in tropical regions • Global sea level is affected by ice ages and plate tectonics How the sea modifies coastlines

26. 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. 1. Wave Action erodes or deposits material along coastlines

27. 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 1. Wave Action erodes or deposits material along coastlines

28. Marine Erosion • Chemical Attack • Abrasion • Wave Impact • Compressed Air • Backwash 1. Wave Action erodes or deposits material along coastlines

29. Water Velocity and Erosion 1. Wave Action erodes or deposits material along coastlines

30. 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 1. Wave Action erodes or deposits material along coastlines

31. Beach Drift, New Jersey

32. 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 2. Types of coastline

33. 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 2. Types of coastline

34. Secondary Coasts Are Modified by Marine Erosion or Deposition

35. Erosion Stack Terraces Tombolo 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 Secondary Coasts 2. Types of coastline

36. Primary Coastlines Are Very Common • Drowned River Valleys (Estuaries) • Drowned Glacial Valleys (Fiords) 2. Types of coastline

37. Estuaries, Chesapeake Bay

38. Tidal Marshes, Chesapeake Bay 2. Types of coastline

39. Fiord Coast, Labrador

40. Other Ways Primary Coasts Can Form • Deltas • Volcanic Activity • Uplift 2. Types of coastline

41. Primary and Secondary Coastlines 2. Types of coastline

42. Baymouth Bar, Michigan

43. Wave-Cut Platform, California Footer

44. Coastal Terraces, California

45. Sea Stacks, Washington

46. Former Stack, Michigan

47. Sea Caves, Apostle Islands

48. Wave-Cut Arch, Lake Superior

49. Delta Coasts • Deposition-Dominated • Wave Dominated • Tide-Dominated 3. Deltas are governed by deposition, waves, and tides

50. The Mississippi – A Deposition-Dominated Delta 3. Deltas are governed by deposition, waves, and tides