(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".
- What three elements make a beach?
- What do most beach materials in North America consist of, and what is the
source of this material?
The Work of the Waves
- What defines the extent of a beach, in Bascom's view?
- What generates most of the waves arriving at a beach?
- What three aspects of the wind determine the size of the waves it can create?
- What is swell? What three properties of swell are used
to characterize it?
- What happens to swell when it enters shallow water (and how shallow is "shallow")?
- What happens when waves break?
- How do waves in shallow water act to change a beach?
The Measurement of Beaches
- What is a beach profile?
- What is the relation between the slope of a beach and the size of its sand
- 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
- What effect do bars have on incoming waves? What effect does this have on
waves reaching the beach?
- What tends to happen to bars in summer? Where does the material in them
- What is swash? How does swash help build the berm?
- What is a rip channel and how does it form? What is a rip
- Is there such a thing as "undertow"? If so, is it dangerous? Why
or why not?
Cusps and Ripple Marks
The Preservation of Beaches
- What is an alongshore current associated with waves, and
how does it form? What effect does it have on sand transport?
- When do alongshore currents transport the most sand?
- What is wave refraction? What does refraction do to waves
entering shallow water along a coastline at an angle?
- What is the typical pattern of motion of sand grains transported by angled
waves and the alongshore current that they produce?
- What is a groin? What purpose is it intended to serve?
Does it work?
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