1. 1 “The sea heaves up, hangs loaded o'er the land, Breaks there, and buries its tumultuous strength. ” ”” ” — Robert Browning Hamilton (Brainyquote.com)

2. 2  The Impact of Waves and Currents on the Landscape  Coastal Processes  Coastal Landforms  Summary Coastal Processes and Terrain

3. 3  The Impact of Waves and Currents on the Landscape Coastal Processes –Erosion – Waves, mainly –Deposition – Currents, mainly Rocky cliffs and headlands –Main erosional features Beaches and sandbars –Main depositional features

4. 4  Coastal Processes Erosion and Deposition –Involve the transfer of energy from the atmosphere to the hydrosphere (ocean) and then to the lithosphere (land). Kinetic energy transfer Wind Deposition Erosion Wind Coast

5. 5 Geomorphic agents –Waves Wind-generated waves Other sources of waves –Other agents Longshore currents Tides and tidal currents Volcanic eruptions and earthquakes Tidal (storm) surges Long-term (tectonic and climatic) effects on sea level change Reef-building corals Sea ice Glaciers

6. 6  Waves Animation Definition – A disturbance in water caused by energy passing through it. Wave terms: wavelength, wave crest and trough, swash 1.Wave Motion and Wave Refraction 2.Tsunami –Fig. 20-2

7. 7 Waves of Oscillation and Translation –Wave of Oscillation – energy and mass move differently H 2 O particles – orbital paths Energy –Fig. 20-2

8. 8 –Wave of Translation – energy and mass move in the same direction (horizontally) –Fig. 20-3 shore

9. 9 –Wave Refraction –Fig. 20-5

10. 10 Side view of headland Headland erosion (idealized) SA Wave Refraction (blue lines) Headland Eroding Sea cave X Sea arch Sea stack SS H SC

11. 11 –Fig. 20-6. Headland erosion in Australia along the southern coast of the state of Victoria.

12. 12 –Wave Erosion Hydraulic pounding Chemical action Sea cliff erosion –Fig. 20-7 Notch Wave-cut platform Cliff face Sea Level Former shore

13. 13 –Tsunami (Seismic Sea Waves) Rapid, pronounced vertical displacement Main causes –Earthquake (submarine) –Landslide (submarine) –Volcanic island eruption Sea level Seafloor Fault Sea level

14. 14 –Fig. 20-8. Formation of a Tsunami.

15. 15 Tides Animation (Tides) –Significant erosion agents in narrow bays, margins of shallow seas, and straits. Fig. 20-9. Bay of Fundy has the highest tidal range in the world. Tidal action created these pedestal rocks on the edge of the bay.

16. 16 Changes in Sea Level and Lake Level –Causes Tectonic uplift or sinking of landmass Eustatic – increase or decrease in the volume of water in the oceans (Pleistocene glaciations). –Fig. 20-10. Northern California coast is experiencing tectonic uplift.

17. 17 –Global Warming and Sea-Level Change Causes –Thermal expansion –Glacial melting Consequences by 2100 –Sea Level rise – Up to 0.5 m (20”) rise –Retreat of shorelines – Up to 30 m (ca. 100 ft.) in some areas. Ice Push –Annual freezing of sea ice causes near-shore ice to push against the land, causing minor erosion – Arctic and Antarctic regions only

18. 18 Organic Substances –Calcium carbonate secretions –Reef-building coral polyps Stream Outflow –Source of sediment for beaches –Fig 20-11. Sediment plume of the Betsiboka River, Madagascar.

19. 19 Currents and Coastal Sediment Transport –Longshore Currents Wave refraction - Energy bends upon entering shallow water shore -2 m -6m -1m Depth Longshore current Undertow diverted by incoming waves

20. 20 –Beach Drifting Particle-by-particle transport of beach material Wave refraction (bending) Beach W1W2W4W3 backwash = sand particle

21. 21 –Fig. 20-13. Waves approaching the shore obliquely causes longshore currents and beach drifting.

22. 22 Coastal Deposition –Sediment budget of a shore Inputs from longshore current supply and wave action Outputs from storm wave action, mainly. –Large beaches and sand dunes Inputs exceed outputs. Fig. 20-14. One of the largest coastal dune complexes is on the Oregon coast. Fig. 20-14

23. 23  Coastal Landforms Depositional Landforms Animation (Coastal Stabilization Structures) –Beaches Most widespread marine dispositional feature on land –Mostly sand deposits Extent –Inland margin (storm wave deposits) –Seaward margin (neap tide line) Sea Level ? ? Extent

24. 24 Components of the beach environment –Fig. 20-15

25. 25 –Spit and related features Spit: Linear strand of marine sediments attached to shore Formation usually involves longshore current transport Related features –Fig. 20-16. Types of spits and the longshore current.

26. 26 Idealized drawings of formation of spit and related features (3) Baymouth bar (2) Hook Land Ocean Bay (1) Simple spit

27. 27 Tombolo formation Land Ocean Small island, sea stack

28. 28 Photographs of spits and related features –Fig. 20-17. Spit at Cape Henlopen, Delaware

29. 29 –Fig. 20-18. Tombolo and Mont Saint Michel on the northwest coast of France.

30. 30 –Barrier Islands Coastal islands, parallel to the mainland shore Complex origins –Pleistocene sediments washed toward mainland –Longshore transport and spit segmentation LandOcean Bay Barrier Island

31. 31 Lagoon formation –Landward side of barrier island, protected from large waves –Low energy environment, fine mud deposits (tidal flats) –Fig. 20-19

32. 32 –Human Alteration of Coastal Sediment Budgets Beach starvation (unintentionally shrinking beaches) –Dam construction on rivers reduces sediment discharge into oceans, starving nearby beaches of sand –Old debris dam in Santa Ynez Mountains, near Santa Barbara, CA (Richard A. Crooker photo)

33. 33 Beach nourishment (re-building beaches) –Adding sand to beaches by dredging and pumping sand from off-shore –A slurry of sand and water is pumped on shore and the sand is spread onto the beach of Rehoboth Beach, DE (Richard A. Crooker photos) (overlay, dissolve)

34. 34 Beach preservation (maintaining beaches) –Build structures that modify longshore transport and wave action in order to keep sand on beaches –Jetty –Groin –Fig. 20-22

35. 35 Shorelines of Submergence –Ria Shorelines Hilly or mountainous areas –flooded valleys become estuaries - Fig. 20-23. Chesapeake Bay.

36. 36 –Fjorded Coasts Fjord – glacial trough that is inundated by the sea –Fig. 20-24

37. 37 –Wave-cut Cliffs and Platforms –Marine Terraces - Fig. 20-27. Near Fort Ross, CA

38. 38 Coral Coasts –Coral Polyps Reef-building varieties, warm tropical waters –Fig. 20-28

39. 39 –Shallow-water Platforms Australia’s Great Barrier Reef –Fig. 20-30

40. 40 –Sinking Islands Three types of reefs Sea Level  Fringing Sea Level  Barrier Sea Level  Atoll

41. 41 –Fig. 20-31

42. 42 –Fig. 20-32. Part of the fringing reef on the island of Moorea, French Polynesia.

43. 43  Summary The principal forces shaping coastlines are changes in sea level, tides, waves, currents, stream outflow, ice push, and organic secretions. Waves cause erosion as they constantly crash onto the shore. Waves and longshore currents transport sediments along a coast.

44. 44 Landforms along coastlines include beaches, wave-cut benches, wave-built terraces, and barrier islands and their lagoons, spits, fjords, and coral reefs.