Page 565 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

Chapter 16 Oceans, Coastal Systems, and Wind Processes 529
flood tides and two low (falling) ebb tides every day. The difference between consecutive high and low tides is the tidal range. Spring tides exhibit the greatest tidal range, when the Moon and the Sun are in either conjunction or op- position. Neap tides produce a lesser tidal range.
littoral zone (p. 496)
mean sea level (MSL) (p. 498) tide (p. 499)
flood tide (p. 500)
ebb tide (p. 500)
spring tide (p. 500)
neap tide (p. 500)
4. What are the key terms used to describe the coastal environment?
5. Definemeansealevel.Howisthisvaluedetermined? Is it constant or variable around the world? Explain.
6. What interacting forces generate the pattern of tides?
7. What characteristic tides are expected during a new Moon or a full Moon? During the first-quarter and
third-quarter phases of the Moon? What is meant by
a flood tide? An ebb tide?
8. Explain briefly how tidal power is used to produce
electricity. Are there any tidal power plants in North America? If so, briefly describe where they are and how they operate.
■ Describe wave motion at sea and near shore, and ex- plain coastal straightening and coastal landforms.
Friction between moving air (wind) and the ocean surface generates undulations of water that we call waves. Wave energy in the open sea travels through water, but the water itself stays in place. Regular patterns of smooth, rounded waves—the mature undula- tions of the open ocean—are swells. Near shore, the re- stricted depth of water slows the wave, forming waves of translation, in which both energy and water actually move forward toward shore. As the crest of each wave rises, the wave falls into a characteristic breaker.
Wave refraction redistributes wave energy along a coastline. Headlands are eroded, whereas coves and bays are areas of deposition, with the long-term effect of these differences being a straightening of the coast. As waves approach a shore at an angle, refraction produces a long- shore current of water moving parallel to the shore. Par- ticles move along the beach as beach drift, shifting back and forth between water and land. The combined action of this current produces the littoral drift of sand, sediment, gravel, and assorted materials along the shore. A tsunami is a seismic sea wave triggered by an undersea landslide or earthquake. It travels at great speeds in the open sea and gains height as it comes ashore, posing a coastal hazard.
An erosional coast features wave action that cuts a horizontal bench in the tidal zone, extending from a sea cliff out into the sea. Such a structure is a wave-cut plat- form, or wave-cut terrace. In contrast, depositional coasts generally are located along land of gentle relief, where depositional sediments are available from many sources. Characteristic landforms deposited by waves and currents are the barrier spit (material deposited in a long ridge ex- tending out from a coast); the bay barrier, or baymouth bar (a spit that cuts the bay off from the ocean and forms an inland lagoon); the tombolo (where sediment deposits
connect the shoreline with an offshore island or sea stack); and the beach (land along the shore where sediment is in motion, deposited by waves and currents).
wave (p. 501)
swell (p. 501)
breaker (p. 502)
wave refraction (p. 503) longshore current (p. 503) beach drift (p. 504) littoral drift (p. 504) tsunami (p. 504)
wave-cut platform (p. 507) barrier spit (p. 508)
bay barrier (p. 508) lagoon (p. 508) tombolo (p. 508) beach (p. 508)
9. What is a wave? How are waves generated, and how do they travel across the ocean? Does the water travel with the wave? Discuss the process of wave formation and transmission.
10. Describe the refraction process that occurs when waves reach an irregular coastline. Why is the coast- line straightened?
11. Describe the process of beach drift and the move- ment of longshore currents to produce littoral drift.
12. Explain how a seismic sea wave attains such tremen- dous velocities. Why is it given the name tsunami?
13. What is meant by an erosional coast? What are the expected features of such a coast?
14. What is meant by a depositional coast? What are the expected features of such a coast?
15. How do people attempt to modify littoral drift? What strategies do they use? What are the positive and negative impacts of these actions?
16. Describe a beach—its form, composition, function, and evolution.
17. Is beach replenishment a practical strategy?
■ Describe barrier beaches and islands and their hazards
as they relate to human settlement.
Barrier chains are long, narrow, depositional features, gen- erally of sand, that form offshore roughly parallel to the coast. Common forms are barrier beaches and the broader, more extensive barrier islands. Barrier formations are transient coastal features, constantly on the move, and they are a poor, but common, choice for development.
barrier beach (p. 511) barrier island (p. 511)
18. What types of impacts did Hurricanes Katrina and Sandy have on barrier beaches and islands in the Gulf and along the Atlantic coast?
19. On the basis of the information in the text and any other sources at your disposal, do you think barrier islands and beaches should be used for develop- ment? If so, under what conditions? If not, why not?
■ Describe the nature of coral reefs and coastal wetlands, and assess human impacts on these living systems.
A coral is a simple marine invertebrate that forms a hard, calcified, external skeleton. Over generations, corals