GEOL/METR 309: Investigating
Land, Sea and Air Interactions
Fall 2005, SFSU

Reading Assignment #6,
Part II: "Beaches",
from Scientific American

 Dr. Dave Dempsey
Dr. Lisa White
(Dept. of Geosciences)
(Read by Thursday, Oct. 20)

Read the accompanying article, "Beaches" by Willard Bascom, August 1960, Scientific American magazine. Use the questions below to guide you to the parts of the reading worth the most attention for the purposes of GEOL/METR 309. You are not responsible for handing in answers to these questions, but they are fair game on an exam, and Pre-class Exercise #5, "Waves and Beaches", is based on these questions and on the questions for the companion reading assignment, "Ocean Waves".

  1. What three elements make a beach?
  2. What do most beach materials in North America consist of, and what is the source of this material?

The Work of the Waves

  1. What defines the extent of a beach, in Bascom's view?

  2. What generates most of the waves arriving at a beach?

  3. What three aspects of the wind determine the size of the waves it can create?

  4. What is swell? What three properties of swell are used to characterize it?

  5. What happens to swell when it enters shallow water (and how shallow is "shallow")?

  6. What happens when waves break?

  7. How do waves in shallow water act to change a beach?

The Measurement of Beaches

  1. What is a beach profile?

  2. What is the relation between the slope of a beach and the size of its sand grains?

  3. What is a bar? What is a berm? How and when (what time of year) do bars form? Where does the material in bars come from?

  4. What effect do bars have on incoming waves? What effect does this have on waves reaching the beach?

  5. What tends to happen to bars in summer? Where does the material in them go?

  6. What is swash? How does swash help build the berm?

  7. What is a rip channel and how does it form? What is a rip current?

  8. Is there such a thing as "undertow"? If so, is it dangerous? Why or why not?

Cusps and Ripple Marks

The Preservation of Beaches

  1. What is an alongshore current associated with waves, and how does it form? What effect does it have on sand transport?

  2. When do alongshore currents transport the most sand?

  3. What is wave refraction? What does refraction do to waves entering shallow water along a coastline at an angle?

  4. What is the typical pattern of motion of sand grains transported by angled waves and the alongshore current that they produce?

  5. What is a groin? What purpose is it intended to serve? Does it work?

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