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Coasts: Beaches and Shoreline Processes

Coasts: Beaches and Shoreline Processes. Coastal Processes. Three Main Coastal Zone Processes controls what features we see along the coasts. Tectonics- 1st order control (i.e., Primary) Geology/rock type- 2nd order control Waves and currents- 3rd order control.

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Coasts: Beaches and Shoreline Processes

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  1. Coasts: Beaches and Shoreline Processes

  2. Coastal Processes • Three Main Coastal Zone Processes controls what features we see along the coasts. • Tectonics- 1st order control (i.e., Primary) • Geology/rock type- 2nd order control • Waves and currents- 3rd order control

  3. Coastal BedrockRates of erosion and deposition (Trujillo & Thurman, 2005)

  4. Tectonics imparts a first order effect on coastal geomorphology • Two major geomorphic types of coastline: • Leading Edge Coasts/ Erosional Coasts • Emergent coasts (uplift) • Trailing Edge Coasts/Depositional Coasts • Submergent coasts (subsidence)

  5. Leading Edge Coasts are characterized by erosional features • Sea cliffs • Marine terraces/ wave cut platforms • Sea Caves • Sea Arches • Narrow shelves • Pocket beaches • Sea stacks and headlands • Small drainage basins, low sediment supply • High gradient with coarse sediment • Tectonic uplift

  6. Schematic drawing of important erosional features (Garrison, 6th ed., Fig. 12.4a)

  7. Wave cut Platforms/Sea Stacks (Garrison, 2005) (Garrison, 6th Ed., Fig. 12.4b-d)

  8. Trailing Edge Coasts are characterized by depositional features • Barrier islands • Tidal marshes, estuaries and inlets • Wide shelves • Broad coastal plains • Long continuous beaches • Large drainage basin, high sediment supply • Low gradient with fine sediment • Subsidence

  9. Depositional features along a trailing edge coast (Garrison, 6th Ed., Fig. 12.19)

  10. Typical Beach Profile (Garrison, 6th Ed., Fig. 12.14)

  11. Beach Profiles Summer Winter (Trujillo & Thurman, 2005. Also a similar figure 12.15 in Garrison, 6th Ed.)

  12. Longshore CurrentBeach a river of sand (Trujillo & Thurman, 2005)

  13. Coastal Cells in Southern California (Garrison, 6th ed., Fig. 12.18b)

  14. Coastal Sediment Transport Cells (Garrison, 6th Ed., Fig. 12.18 a and c)

  15. Rip Currents (Trujillo & Thurman, 2005)

  16. Environmental Aspects of the Coastal Zone • The coastal zone is in a dynamic equilibrium • Therefore most features are ephemeral, both • Natural ephemeral features • Man-made features

  17. Natural Ephemeral Features • Tombolos • Splits • Barrier Islands (Garrison, 6th Ed., Fig. 12.19)

  18. Man-made features/Construction in the coastal zone • Main reasons for construction in the coastal zone: • Improve navigation • Reduce coastal erosion • Aesthetics

  19. Main man-made structures • Jetties/Groins • Breakwaters • Sea Walls/Rip-rap

  20. Jetties and Groins (Trujillo & Thurman, 2005)

  21. Breakwater Santa Monica, CA (Trujillo & Thurman, 2005)

  22. Seawalls versus Beach Re-nourishment (Garrison, 6th Ed., Fig. 12.36)

  23. Changes in Sea Level • Seconds/Minutes • Waves • Daily • Tides, winds, storms • Yearly (annual) • Climatic effects, changes in temperature and density (e.g. 3-4” drop during upwelling, CA) • 103 years • Glacioeustatic • 106 years • Geoeustatic

  24. Eustacy= Global change in sea level • Glacioeustatic = change in volume of water in the ocean basins (i.e., glacial cycles) • Geoeustatic= change in the volume of the ocean basin (i.e., tectonic cycles)

  25. Sea level curve last 250,000 years (Garrison, 6th Ed., Fig. 4.15)

  26. Florida in the Past and Distant Future (Garrison, 6th Ed., Fig. 12.2)

  27. Estuaries • Define an estuary? • A protected coastal body of water with freshwater input at its head and seawater input at its mouth.

  28. Origin of Estuaries • Coastal plain estuaries/Drowned river valleys • e.g., Tampa bay; Chesapeake Bay • Fjords/Glaciated U-shaped valley • e.g., Strait of Juan de Fuca, WA; Norway • Bar-built estuaries/Coastal lagoons • e.g., Albemarle and Pamlico Sounds, NC • Tectonic/Fault block estuaries • e.g., San Francisco Bay and Tomales Bay, CA

  29. Estuaries classification by origin (Garrison, 6th Ed., Fig. 12.30)

  30. Drowned River Valleys (Trujillo & Thurman, 2005)

  31. Classification of Deltas (Garrison, 6th Ed., Fig. 12.25)

  32. River Dominated Delta/Mississippi (Garrison, 6th Ed., Fig. 12.24a)

  33. Wave Dominated Delta/Nile (Trujillo & Thurman, 2005)

  34. Tide Dominated Delta/ Ganges (Garrison, 6th Ed., Fig. 12.24b)

  35. Types of Coral Reef Coasts (Garrison, 6th Ed., Fig. 12.28)

  36. Examples of a Fringing Reef and an Atoll (Garrison, 5th Ed., Figs. 12.26 and 12.27)

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