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  1. 1. Chapter 20: Coastal Processes and Landforms Physical Geography Ninth Edition Robert E. Gabler James. F. Petersen L. Michael Trapasso Dorothy Sack
  2. 2. Coastal Processes and Landforms <ul><li>Large percentage of world’s population lives near the coast </li></ul>
  3. 3. 20.1 The Coastal Zone <ul><li>Shoreline </li></ul><ul><li>Sea Level </li></ul><ul><ul><li>Average position of shoreline </li></ul></ul><ul><li>Coastal zone </li></ul><ul><ul><li>Nearshore zone </li></ul></ul><ul><ul><li>Breaker zone </li></ul></ul><ul><ul><li>Surf zone </li></ul></ul><ul><ul><li>Swash zone (backwash) </li></ul></ul><ul><ul><li>Offshore zone </li></ul></ul>
  4. 4. 20.2 Origin and Nature of Waves <ul><li>Waves </li></ul><ul><ul><li>Wave crests </li></ul></ul><ul><ul><li>Wave troughs </li></ul></ul><ul><ul><li>Wave height </li></ul></ul><ul><ul><li>Wavelength </li></ul></ul><ul><ul><li>Wave steepness </li></ul></ul><ul><ul><li>Wave period </li></ul></ul><ul><li>Tides </li></ul><ul><li>Tsunamis </li></ul><ul><li>Wind waves </li></ul>
  5. 5. 20.2 Origin and Nature of Waves <ul><li>Tides </li></ul><ul><ul><li>Gravitational pull of the moon and sun is the force that causes tides </li></ul></ul><ul><ul><li>Moon has a stronger pull </li></ul></ul><ul><ul><li>Centrifugal force </li></ul></ul><ul><ul><li>Tidal range </li></ul></ul><ul><ul><ul><li>Difference in sea level between high and low tide </li></ul></ul></ul>
  6. 6. 20.2 Origin and Nature of Waves <ul><li>Spring tide </li></ul><ul><li>Neap tide </li></ul><ul><li>Q: How many spring tides and neap tides occur each month? </li></ul>
  7. 7. 20.2 Origin and Nature of Waves <ul><li>Tides </li></ul><ul><ul><li>Semidiurnal tide </li></ul></ul><ul><ul><li>Diurnal tide </li></ul></ul><ul><ul><li>Mixed tide </li></ul></ul><ul><ul><li>Q: What is the tidal pattern on the coastal area nearest where you live? </li></ul></ul>
  8. 8. 20.2 Origin and Nature of Waves <ul><li>Tidal range varies due to: </li></ul><ul><ul><li>Shape of coastline </li></ul></ul><ul><ul><li>Water depth </li></ul></ul><ul><ul><li>Access to open ocean </li></ul></ul><ul><ul><li>Submarine topography </li></ul></ul><ul><li>Largest tidal range (Bay of Fundy, Canada) </li></ul>
  9. 9. 20.2 Origin and Nature of Waves <ul><li>Tsunamis </li></ul><ul><ul><li>Long-wavelength waves that form when a large mass of water displaced upward of downward by: </li></ul></ul><ul><ul><ul><li>Earthquakes </li></ul></ul></ul><ul><ul><ul><li>Volcanic eruptions </li></ul></ul></ul><ul><ul><ul><li>Landslide </li></ul></ul></ul><ul><ul><li>December, 2004 Indonesia earthquake and tsunami </li></ul></ul>
  10. 10. 20.2 Origin and Nature of Waves <ul><li>Wind Waves </li></ul><ul><ul><li>Most waves on surface of standing body of water created by wind </li></ul></ul><ul><ul><li>Frictional drag and pressures cause irregularities in the water surface </li></ul></ul><ul><ul><li>Waves can travel thousands of miles </li></ul></ul><ul><ul><li>3 Factors determine height of wind waves </li></ul></ul><ul><ul><ul><li>Wind velocity </li></ul></ul></ul><ul><ul><ul><li>Duration of wind </li></ul></ul></ul><ul><ul><ul><li>Fetch </li></ul></ul></ul>
  11. 11. 20.2 Origin and Nature of Waves <ul><li>Waves are traveling forms </li></ul><ul><li>Deep-water </li></ul><ul><li>Wave base </li></ul>
  12. 12. 20.2 Origin and Nature of Waves <ul><li>Why don’t the waves break in deeper water? </li></ul>
  13. 13. 20.3 Breaking Waves <ul><li>Rip currents </li></ul><ul><ul><li>Relatively narrow zones of strong, offshore-flowing water </li></ul></ul><ul><ul><li>Q: Why are these currents a hazard to swimmers? </li></ul></ul>
  14. 14. 20.4 Wave refraction and Littoral drifting <ul><li>Wave refraction </li></ul><ul><ul><li>Bending of a wave in map view as it approaches a shoreline </li></ul></ul><ul><ul><li>Q: How will this coastline change over a long period of time? </li></ul></ul>
  15. 15. 20.4 Wave refraction and Littoral drifting <ul><li>Wave refraction </li></ul><ul><ul><li>Coastlines tend to straighten over time </li></ul></ul><ul><ul><li>Q: What happens to sediment eroded from the headlands? </li></ul></ul>
  16. 16. 20.4 Wave refraction and Littoral drifting <ul><li>Not all waves refract completely before they break </li></ul><ul><li>Littoral drifting </li></ul><ul><ul><li>Incomplete refraction produces sediment transport in the coastal zone </li></ul></ul>
  17. 17. 20.4 Wave refraction and Littoral drifting <ul><li>When a wave crest approaches a straight, gently sloping shoreline at a large angle, it interacts with the bottom and starts to slow down </li></ul><ul><li>Beach drifting </li></ul><ul><li>Longshore current </li></ul><ul><li>Longshore drifting </li></ul>
  18. 18. 20.5 Coastal Erosion <ul><li>Key Terms </li></ul><ul><ul><li>Corrosion </li></ul></ul><ul><ul><li>Hydraulic action </li></ul></ul><ul><ul><li>Abrasion </li></ul></ul><ul><li>Coastal Erosional Landforms </li></ul><ul><ul><li>Coasts of high relief are dominated by erosion </li></ul></ul><ul><ul><li>Sea cliffs (or lake cliffs) </li></ul></ul>
  19. 19. 20.5 Coastal Erosion <ul><li>Coastal Erosional Landforms </li></ul><ul><ul><li>Notch </li></ul></ul><ul><ul><li>Cobble beach </li></ul></ul><ul><ul><li>Sea caves </li></ul></ul>
  20. 20. 20.5 Coastal Erosion <ul><li>Coastal Erosional Landforms </li></ul><ul><ul><li>Sea arches </li></ul></ul><ul><ul><li>Sea stack </li></ul></ul>
  21. 21. 20.5 Coastal Erosion <ul><li>Coastal Erosional Landforms </li></ul><ul><ul><li>Abrasion platform </li></ul></ul><ul><ul><li>Marine terraces </li></ul></ul>
  22. 22. 20.6 Coastal Deposition <ul><li>Coastal Deposition </li></ul><ul><ul><li>Sediments accumulate where wave energy is low </li></ul></ul><ul><ul><li>3 principal sources of coastal sediment: </li></ul></ul><ul><ul><ul><li>Streams </li></ul></ul></ul><ul><ul><ul><ul><li>Delta </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Estuary </li></ul></ul></ul></ul><ul><ul><ul><li>Coastal cliff erosion </li></ul></ul></ul><ul><ul><ul><li>Offshore sources </li></ul></ul></ul>
  23. 23. 20.6 Coastal Deposition <ul><li>Coastal Depositional Landforms </li></ul><ul><ul><li>Beach </li></ul></ul><ul><ul><ul><li>Most common form </li></ul></ul></ul><ul><ul><ul><li>Wave-deposited feature </li></ul></ul></ul><ul><ul><ul><li>Sandy beach </li></ul></ul></ul><ul><ul><ul><li>Cobble beach </li></ul></ul></ul>
  24. 24. 20.6 Coastal Deposition <ul><li>Coastal Depositional Landforms </li></ul><ul><ul><li>Middle latitudes beaches are generally narrower, steeper and composed of coarser material in winter compared to summer </li></ul></ul><ul><ul><li>Longshore bar </li></ul></ul>
  25. 25. 20.6 Coastal Deposition <ul><li>Coastal Depositional Landforms </li></ul><ul><ul><li>Spits </li></ul></ul><ul><ul><li>Tombolo </li></ul></ul>
  26. 26. 20.6 Coastal Deposition <ul><li>Coastal Depositional Landforms </li></ul><ul><ul><li>Barrier beaches </li></ul></ul><ul><ul><li>Lagoons </li></ul></ul><ul><ul><li>Barrier spit </li></ul></ul><ul><ul><li>Barrier islands </li></ul></ul>
  27. 27. 20.6 Coastal Deposition <ul><li>Coastal Depositional Landforms </li></ul><ul><ul><li>Barrier Islands </li></ul></ul><ul><ul><ul><li>Locations: Atlantic (Cape Hatteras) and gulf coasts </li></ul></ul></ul><ul><ul><ul><li>Change drastically with severe storms </li></ul></ul></ul>
  28. 28. 20.6 Coastal Deposition <ul><li>Coastal Depositional Landforms </li></ul><ul><ul><li>Beach systems </li></ul></ul><ul><ul><ul><li>Equilibrium when input and output of sediment are equal </li></ul></ul></ul><ul><ul><ul><li>Groin </li></ul></ul></ul><ul><ul><ul><ul><li>Human made obstruction of longshore current (increases size of some beaches) </li></ul></ul></ul></ul>
  29. 29. 20.7 Types of Coasts <ul><li>Coastal Classification is based on plate tectonics </li></ul><ul><ul><li>Passive-margin </li></ul></ul><ul><ul><ul><li>Low relief and broad coastal plain </li></ul></ul></ul><ul><ul><ul><li>Continental shelves </li></ul></ul></ul><ul><ul><ul><li>e.g. East Coast </li></ul></ul></ul><ul><ul><li>Active-margin </li></ul></ul>
  30. 30. 20.7 Types of Coasts <ul><li>Coastal Classification </li></ul><ul><ul><li>Active-margin </li></ul></ul><ul><ul><ul><li>High relief and narrow coastal plain </li></ul></ul></ul><ul><ul><ul><li>e.g. West Coast of U.S. along Pacific Ocean </li></ul></ul></ul>
  31. 31. 20.7 Types of Coasts <ul><li>Coastal Classification </li></ul><ul><ul><li>Regional scale </li></ul></ul><ul><ul><li>Coastlines of emergence </li></ul></ul><ul><ul><ul><li>Water level has fallen or the land has risen </li></ul></ul></ul><ul><ul><ul><li>Best developed along active-margin coasts (e.g. west coast of U.S) </li></ul></ul></ul>
  32. 32. 20.7 Types of Coasts <ul><li>Coastal Classification </li></ul><ul><ul><li>Regional scale </li></ul></ul><ul><ul><li>Coastlines of submergence </li></ul></ul><ul><ul><ul><li>Many features of the former shore are present </li></ul></ul></ul><ul><ul><li>2 types of submerged coastlines </li></ul></ul><ul><ul><ul><li>Rias coasts </li></ul></ul></ul><ul><ul><ul><li>Fjord coasts </li></ul></ul></ul>
  33. 33. 20.7 Types of Coasts <ul><li>Fjord coasts </li></ul><ul><ul><li>Highly irregular </li></ul></ul><ul><ul><li>Deep, steep sided arms </li></ul></ul><ul><ul><li>Locations: Norway, Alaska, Chile, and Canada </li></ul></ul>
  34. 34. 20.7 Types of Coasts <ul><li>Another Regional classification system of coasts </li></ul><ul><ul><li>Primary coastline </li></ul></ul><ul><ul><ul><li>Erosion and deposition dominant </li></ul></ul></ul><ul><ul><ul><li>Result from rapid changes in coastline </li></ul></ul></ul><ul><ul><li>Secondary coastline </li></ul></ul><ul><ul><ul><li>Formed by waves and aquatic organisms </li></ul></ul></ul>
  35. 35. 20.8 Islands and Coral Reefs <ul><li>Three basic ocean types of islands </li></ul><ul><ul><li>Continental </li></ul></ul><ul><ul><ul><li>Geologically apart of continent </li></ul></ul></ul><ul><ul><ul><li>Examples: Greenland, Great Britain, New Guinea, and Borneo </li></ul></ul></ul><ul><ul><li>Oceanic </li></ul></ul><ul><ul><li>Atolls </li></ul></ul>
  36. 36. 20.8 Islands and Coral Reefs <ul><li>Oceanic </li></ul><ul><ul><li>Volcanoes that rise from deep ocean floor </li></ul></ul><ul><ul><li>Along trenches: Aleutians, Tonga, Marianas </li></ul></ul><ul><ul><li>Along mid-ocean ridges: Iceland, Azores </li></ul></ul><ul><ul><li>Along chains: Hawaiian islands </li></ul></ul>
  37. 37. 20.8 Islands and Coral Reefs <ul><li>Atoll </li></ul><ul><ul><li>Island consisting of a ring of coral reefs </li></ul></ul><ul><ul><li>Grown up from a subsiding volcanic island </li></ul></ul><ul><ul><li>Encircle a central lagoon </li></ul></ul>
  38. 38. 20.8 Islands and Coral Reefs <ul><li>Coral Reefs </li></ul><ul><ul><li>Shallow, wave-resistant structures </li></ul></ul><ul><ul><li>Remains of tiny sea animals (skeleton of calcium carbonate) </li></ul></ul><ul><ul><li>Types of Reefs </li></ul></ul><ul><ul><ul><ul><li>Fringing reef </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Barrier reef </li></ul></ul></ul></ul><ul><ul><li>Challenge for human habitation </li></ul></ul>
  39. 39. Physical Geography End of Chapter 20: Coastal Processes and Landforms

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