Coastal Landforms

1. Coastal Landforms

3. Basic Concepts • I. Sea level changes repeatedly • 422 ft. eustatic rise since 18,000 years ago. • specific landscapes submergent or emergent depending on tectonic change • II. Waves and resultant currents erode, transport, and deposit sediment load. • rocky headlands • beaches • III. Tides affect all coastal life but have little topographic effect. • tidal bores

4. Eustatic Change and Submergent vs. Emergent Coastlines • during ice ages sea level sinks as ocean water compresses and more water is tied up in glaciers. • During interglacial periods sea level rises, flooding many former river valleys creating bays and estuaries. • In areas with rapid tectonic uplift emergent cliffs common and bays rare.

5. Submergent Coastlines Sea level rise inundated many coastal valleys creating bays and estuaries. These coasts are referred to as ria coastlines. Estuary - An arm of the sea that extends inland to meet the mouth of a river.

6. Emergent Coastlines Tectonic forces lift coastlines faster than sea-level rises. Dramatic cliffs and marine terraces tower above the sea.

8. Coastal Erosion - dependent on wave size, angle, and frequency. Focused where waves contact coast. • Headlands, sea cliffs, bluffs, sea stacks, natural bridges • Beach Erosion • Coastal Transportation - wave action creates strong currents parallel to shore. Large waves move beach sand offshore. Small waves push it back on shore. • Longshore current • Coastal Deposition – where wave action is reduced, beaches and dunes form. • beaches • dunes • sand spits COASTAL FLUVIAL PROCESSES/LANDFORMS

14. Isla Vista Beach, October 2001

15. Isla Vista Beach, December 2002

16. Beach Erosion

18. Marine Terraces

19. Point Reyes National Seashore

20. Wave Refraction - waves change directional trend as they approach shore. Raglan, New Zealand

23. Tombolo

24. Tombolo

25. Sand Spit

26. Sand Spit

27. Sand Spit

28. Sea Stacks

29. Natural Bridges and Arches

30. Barrier Islands

31. Barrier Islands

32. Outer Banks, North Carolina

33. Tropical Coasts

34. Factors Correlated with Healthy Coral Reef Growth • water temperature range: 18 – 29C • normal seawater salinity: 32 – 35 ‰ • clear, transparent water • little or no sedimentation • vigorous water motion

42. Tropical Mangroves

43. Mangroves create tidal forests. These rich ecosystems provide habitat for countless creatures and help to stabilize and, by catching sediment, even create coastline.

44. Tides Tides rise and fall with the rising moon, an interval of 24 hours and 50 minutes. There is a bulge on both sides of the earth. Thus two high tides each cycle. Flood tide (low to high) takes 6:13 and then ebb tide (back to low) is another 6:13.

45. Tides Tide range dependent on relative position of earth, moon, and sun. Spring Tides - highest tidal range Neap Tides - lowest tidal range

46. Tides Tide range dependent on relative position of earth, moon, and sun. Spring Tides - highest tides. Neap Tides - lowest tides. Full Moon Half Moon

47. Tides Low Tide, New Brunswick

48. Tides