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1.5.4 Understand how ocean waves and currents change coastlines. (Chapter 3)

1.5.4 Understand how ocean waves and currents change coastlines. (Chapter 3). Coastlines. Two general categories of coastlines:

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1.5.4 Understand how ocean waves and currents change coastlines. (Chapter 3)

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  1. 1.5.4 Understand how ocean waves and currents change coastlines. (Chapter 3)

  2. Coastlines • Two general categories of coastlines: • 1.) Emerging: Water deepens rapidly. Steep banks, as the coast rises up quickly. Fairly straight and rocky shore. Called a regular shoreline. No natural harbors

  3. Emerging Coastlines: What they Shape…a review • Erosion of headlands creates sea caves, sea arches and sea stacks • Emerging coastlines straighten the coastline in much the same fashion as submerging coastlines.

  4. 2.) Submerged: Also know as drowned, embayed or ria coast. Gentle or gradual coastline. What were once river valleys produce an indented and irregular coastline

  5. * 1.5.4 The processes straightens out an irregular coastline. (Submerging coastlines) 1. Weathering of Headland • What forces cause the weathering & erosion? • Hydraulic pressure • Corrosion • Abrasion 2. Transportation of silt • How is silt transported? • Longshore Drift • Waves • Currents 3. Deposition of silt • Where does deposition occur? • Bay beaches; filling inlets • Bay bars; closing off inlets 4. Summary: Submerged coasts straighten!

  6. 1.5.4 Define the terms bay beach, bay bar and spit. (P. 44-45) Bay Beach • An accumulation of sediment in a bay that is deposited by waves and longshore drift. • Spit • A ridge of sand running away from the coast, usually with a curved seaward end. Spit grows in the prevailing direction of longshore drift. Ends are curved by the action of waves in different directions • Bay Bar • A ridge of mud sand or silt extending across a bay. • Formed when spits stretch across the mouth of the bay

  7. Spit • What can you tell about the direction of long shore drift? • Is there any indication a bay bar might form?

  8. Bay Bar • Notice the spit has closed off the mouth of the harbor/bay • Would these be a tourist attraction or distraction?

  9. Bay Beach 2. The point of land on top of the picture would be called? • Where does all the beach sand come from? Can you propose two sources?

  10. 1.5.4 Describe the three processes by which Waves erodes coastal areas. (same as rivers) 1. Hydraulic pressure is the pounding force of water and waves • Corrosion (formation of solutions) is the weathering of rock by chemical processes. Minerals such as calcium carbonate & limestone dissolve in water • Abrasion is an example of physical weathering. Rock & sand particles suspended in the water bump, grind, scrape & gouge surfaces the water hits

  11. Analyze the processes that result in the straightening out of a regular and irregular coastline. • Similarities: • Emerging coastlines straighten, due to erosion and weathering, as do submerging coastlines. • Headlands are reduced in size. • Differences: • Erosion of headlands creates sea caves, sea arches and sea stacks, instead of bay beaches, spits & bay bars.

  12. Questions • Read pp.41-42 • Do: Questions 11, 12 and 13a) • Do: • Page 25. Questions 2 and 3 • Page 26. Question 4a • Page 28. Question 5 • Page 29-30. Case Study. The Red River Flood of 1997. Questions 7a, b, c and d

  13. Answers! • Page 42 • Q11: • A) Process causes waves bend? • Wave refraction • B) Where and Why? • Near shore and headlands • C) Concentrates erosion on the headlands

  14. Q12: • Process causes waves to move eroded sediment along shore? • Longshore drift • Q13A: • Land that juts out? • Headland

  15. Page 25. Questions 2 and 3 • Q#2: • Solutions: Acids • Hydrolysis: Clay/silicates • Oxidation: Rust (red or green). AND weathering of rock!

  16. Page 25: Q#3 • 2.3 Exfoliation: Peeling layers of rock • 2.4 Oxidation: Weathering of rock. (Page 25 note in text)

  17. Page 26. Q#4A • What is drainage basin? • Rainwater absorbed by the soil that runs into a river

  18. Page 28: Q#5 • Identify the river: • Mature River: broad, flat, wide flood plain, large meanders

  19. Page 29-30. Case Study. The Red River Flood of 1997. Questions 7a, b, c and d • 7A) Life stage? Mature or old. Broad meanders, flat floodplain • 7B) Distinguish? Ancient lake with clay bottom. Narrow deep waters. Through Winnipeg, which increases run-off • 7C) Human actions? $63 million floodway/dike • 7D) Further protect? More dikes. Restricting construction. Raising homes. Developing disaster plans. Justify opinion

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