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Chapter 20 Coastlines and Ocean Basins

Chapter 20 Coastlines and Ocean Basins. About Coastlines and Ocean Basins Coastal processes are the interaction of the climate system and the solar system. Waves and tides are key processes at the coastline. The ocean basin contains features like mountains, valleys, and volcanoes.

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Chapter 20 Coastlines and Ocean Basins

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  1. Chapter 20 Coastlines and Ocean Basins

  2. About Coastlines and Ocean Basins • Coastal processes are the interaction of the climate system and the solar system. • Waves and tides are key processes at the coastline. • The ocean basin contains features like mountains, valleys, and volcanoes.

  3. Lecture Outline • How ocean basins differ from continents • 2. Coastal processes • 3. The shaping of shorelines • 4. Continental margins • 5. Topography of the deep sea floor • 6. Ocean sedimentation

  4. How Ocean Basins Differ • from Continents ● Lack of fragmentation processes ● slow chemical weathering ● Limited tectonic activity ● mid-ocean ridges and subduction zones ● Oceans dominated by volcanism and sedimentation

  5. 2. Coastal Processes ● Wave motion – key to shoreline dynamics ● Wind waves: depends on wind speed, duration, and distance

  6. Coastal Processes: Straight Sandy Beach Pea Island, North Carolina

  7. Coastal Processes: Rocky Coastline Mount Desert Island, Maine

  8. Coastal Processes: Wave Erosion Effects Port Campbell, Australia

  9. Coastal Processes: Reef and Beach BEACH REEF southern Florida

  10. 2. Coastal Processes ● To describe a wave ● wavelength ●wave height ●period for successive waves

  11. 2. Coastal Processes ● The velocity of a wave (V) ● V = L x T ●L = wavelength ●T = period

  12. 2. Coastal Processes ● The surf zone ● nearshore area ●waves break (collapse) as they approach the shore ●swash and backwash on shore

  13. 2. Coastal Processes: Wave Motion Near Shore

  14. 2. Coastal Processes: Wave Motion Near Shore

  15. 2. Coastal Processes ● Longshore currents (parallel to shore) ● caused by wave approach at an angle to the shore ●zig-zag path of swash and backwash occurs at the shore ●Rip currents (perpendicular to shore)

  16. 2. Coastal Processes: Wave Motion Near Shore

  17. 3. The Shaping of Shorelines: The Structure of Beaches

  18. 3. The Shaping of Shorelines ● Sand budget of the beach ● incessant movement ●input and output (erosion and sedimentation) ●changing conditions lead to growth or shrinkage

  19. 3. The Shaping of Shorelines ● Erosional coastal forms ● sea cliffs and wave-cut terraces ●Depositional coastal forms ●barrier islands and spits

  20. Shorelines: Four Wave-Cut Terraces California

  21. Shorelines: Sand Spit and Barrier Islands Cape Cod, Massachusetts

  22. 3. The Shaping of Shorelines ● Shoreline erosion and deposition ● uplift / subsidence ●nature of rocks or sediments ●changes in sea level ● average storm wave heights ● heights of tides

  23. 2. Coastal Processes ● The tides: gravitational origin ● solar tides ●lunar tides: spring and neap

  24. 2. Coastal Processes ● Tidal currents ● flood tidal current ●ebb tidal current

  25. 2. Coastal Processes: Bulging Water of the Tides

  26. 2. Coastal Processes: Spring Tides

  27. 2. Coastal Processes: Neap Tides

  28. 4. Continental Margins ● Continental shelves ● low sloping offshore area ●economically important ●Continental slope and rise ● canyons and submarine fans ● turbidity flows of sediment

  29. Continental Margins: Submarine Canyons SHELF SLOPE RISE offshore New England

  30. 5. Topography of the Deep Sea Floor ● How we know about the deep ● Deep Sea Drilling Project ●Ocean Drilling Program ●ship-towed instruments ● deep-diving submarines ● satellite charting of seafloor

  31. 5. Topography of the Deep Sea Floor

  32. 5. Topography of the Deep Sea Floor ● Important features ● mid-ocean ridges ●volcanic tracks of hot spots ●deep sea trenches ● island arcs ● continental margins

  33. 5. Topography of the Deep Sea Floor

  34. 6. Ocean Sedimentation ● Continental shelf sedimentation ● clastics from land ● biochemical ● Deep-sea sedimentation ● pelagic sediments and foraminiferal oozes ● windblown silt and clay ● siliceous oozes (silica plankton)

  35. Oceanic Sediments: Oceanic Ooze Made of Planktonic Organisms

  36. 6. Ocean Sedimentation: Chemical Weathering and Depth

  37. Chapter 21 Glaciers: The Work of Ice

  38. About Glaciers and the Work of Ice • Glacial erosion creates an enormous amount of sedimentary debris. • Ice covers only 10% of Earth now, but 21,000 years ago, the coverage was 30%. • The landscapes of vast areas of many continents have been sculpted by the flow of ice in glaciers.

  39. Lecture Outline • Ice as a rock • 2. How glaciers form • 3. How glaciers move • 4. Glacial landscapes • 5. Glacial cycles and climate change

  40. 1. Ice as a Rock ● Could be viewed as any kind of rock ● igneous – formed from a liquid ● sedimentary – formed in layers ● metamorphic – transformed by pressure and recrystallization

  41. Ice as a Rock: Ice Under Microscope

  42. 1. Ice as a Rock ● Formation of glacial ice ● falls as snow and ice ● recrystallizes over time to ice ● with pressure of overlying ice, ice under pressure starts to flow like a very viscous fluid

  43. 1. Ice as a Rock ● Peculiar properties of the rock ice ● freezes at very low temperature compared to other rocks ● ice is less dense than the liquid it comes from (water)

  44. 1. Ice as a Rock ● Types of glaciers ● valley glaciers (alpine glaciers) ● continental glaciers (ice sheets) ● ice shelves and ice caps

  45. Ice as a Rock: A Valley Glacier near Juneau, Alaska

  46. Ice as a Rock: The Ice Cap of Greenland

  47. 2. How Glaciers Form ● Basic ingredients: cold and snow ● accumulation and ablation ● Glacial movement (glacial budget) ● advance or recession

  48. How Glaciers Form: The Evolution of Snow into Glacial Ice

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