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Shore Zones

Shore Zones. Importance of the Ocean. Source of recreation. Source of water. Affects climate (El Nino and La Nina). Source of food. Dump for waste. EROSION. Movement of material and debris. Definitions. DEPOSITION. Putting material down in layers. WAVES.

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Shore Zones

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  1. Shore Zones

  2. Importance of the Ocean • Source of recreation • Source of water • Affects climate (El Nino and La Nina) • Source of food • Dump for waste

  3. EROSION Movement of material and debris Definitions • DEPOSITION • Putting material down in layers • WAVES • Agents of erosion and deposition; rhythmic surges of water caused mainly by winds

  4. Alaskan Tide Marker

  5. Changing Shore Zones Wave size affects actions: • Low, Gentle - deposit sand • Large, Stormy - carry sand away

  6. Longshore Current • Close to shore • Parallel to shore • Carry sediment away (could be tons) • Will carry sediment until it hits a natural obstacle or a man-made object (groyne)

  7. Longshore Current Wind blows toward the shore, creating waves • Waves move sediment towards the shore at an angle (oblique) • Backwash (retreating waves) carry sediment away from beach at 90°, perpendicular to the shore • The effect of these processes is longshore transport (beach drift) of sediment parallel to shore in the general direction of the prevailing winds

  8. Longshore Current

  9. Longshore Current • Think going to the beach – AAHHHHH!! • Putting your blanket and stuff down on the beach • Run in the water and stay for a while • When you come out – “WHERE IS MY STUFF!?” • It is back up the beach a ways – you have been moved down the beach by the longshore current!

  10. Longshore Current • Energy transferred to the object - sediment drops out • Sediment builds up on the up-drift side of a groyne and enlarges a beach

  11. What will this beach look like over time? Predict Ipswich Bay Direction of waves Plum Island Newbury, MA

  12. Figure 12-2 • Sediments build up on the up-drift side of the groyne enlarging the beach. The normal supply of drift sand is cut off on the down-drift side. The shoreline ends up eroding more quickly. Would placing groynes close together or far apart best help solve this problem?

  13. Placing groynes close together allows the up-drift sediment catch of one groyne to reach the down-drift sediment of the preceding groyne. Shore Ocean Current direction

  14. Groynes Base of Cape Hatteras Lighthouse

  15. New Jersey

  16. Norfolk, VA

  17. Ocean City, NJ

  18. Breakwater

  19. Breakwater, Italy

  20. Breakwater Italy

  21. If 200million waves hit a given rock in your lifetime, how many waves will hit the rock in a year? 2,666,667 Lifetime = 75 years a week? 51,282 a day? 7,326 an hour? 305

  22. Now assume that one hundred waves remove one milligram of rock. About how much rock will be removed in an hour? 3 milligrams day? 73 milligrams Convert this to pounds 1 Kg = 2.2 lbs. week? 513 milligrams year? 26,667 milligrams 75 years? 2,000,000 milligrams

  23. Steep ShoreZones • Rocks and Cliffs are the most common feature • Granite resists weathering and erosion - tend to wear down slowly • Sea Caves • Arches • Small islands of rock

  24. California shoreline

  25. California shoreline

  26. California shoreline

  27. California shoreline

  28. California shoreline

  29. California shoreline

  30. Oregon Coast

  31. Oregon, 1890

  32. Oregon, 1910

  33. Oregon, 1970

  34. Oregon, 1990

  35. Flat Shore Zones • Wide, sandy beach

  36. Beaches • Winter – Large, destructive waves erode sand • Summer – Quiet, gentle waves deposit sand

  37. Beaches • Most beach sand consists of: • light-colored quartz and feldspar sand grains, the result of weathering and erosion of rocks such as granite. • fragments of smoothed and rounded clam shells, and the shells of other marine creatures • Tropical beaches - often consist entirely of shell and coral fragments • Volcanic Areas - Beaches may be black, its sand created by weathering & erosion of basalt, an extrusive igneous rock.

  38. Make of beaches Size of the Particles • Sand - 1/16 - 2 mm • Granules - 2 - 4 mm • Pebbles - 4 - 64 mm • Cobbles - 64 - 256 mm

  39. B E A C H E S

  40. Spit Sandy bar built by currents into a bay from a headland

  41. Spit

  42. Spit

  43. Baymouth Bar A narrow ridge of sand that stretches completely across the mouth of a bay.

  44. Tombolo A narrow ridge of sand that connects an island that was once off-shore with the main land.

  45. Check Your Understanding 1. How do longshore currents form? Longshore currents form where waves moving at a slight angle toward the shore meet water moving away from the shore.

  46. 2. Contrast the characteristics of a steep or rocky shore zone with those of a flat shore zone. Steep shore zones are characterized by cliffs and features carved from the cliffs by waves. Flat shore zones are characterized by sandy beaches.

  47. 3. Are all beach sands alike? Beach sands vary according to the source materials from which they originate.

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