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Home , Longshore drift, Rip tide

101 Linda Khandro, MAT

Homework 9: The (20 points) NAME:______

You will need the following 4 web resources for this Homework:

I. Breaking Waves (plunging and spilling breakers): http://en.wikipedia.org/wiki/Breaking_wave

II. Longshore Currents and : http://en.wikipedia.org/wiki/Longshore_drift

III. Rip Currents: http://en.wikipedia.org/wiki/Rip_current, and http://oregonstate.edu/dept/ncs/newsarch/2007/Jul07/ripcurrents.html

IV. For movies and still photos for all the questions below, go to my Online Oceanography BLOG: http://onlineocean.blogspot.com/. Scroll down until you see the movie and still photo postings for HW 10. Study all the movies and still photos to answer the questions.

Questions:

A. Plunging Breakers: (5 points)

1. Which of the on the blog illustrate, for the most part, “plunging” breakers?

2. Which of the beaches with plunging breakers clearly show(s) a steep face?

3. What is the significance (or relationship) of this kind of beach slope with respect to the plunging breakers?

B. Spilling Breakers: (5 points)

1. Which of the beaches above illustrate, for the most part, “spilling” breakers?

2. Characterize the general slope of these beaches?

3. What is the significance (or relationship) of this kind of beach slope with respect to the spilling breakers? (

C. Breakers: (3 points) In the Puerto Morelos Reef pictures, you can see surf breaking on an offshore reef.

1. What kind of breakers are these, plunging or spilling?

2. Based on your answer to Question C, 1 above, what would you surmise about the seaward slope of this reef?

D. Rip ( or currents?): (7 points, 1 per question) At the beach called Playa Grande, you will see a red warning sign, advising guests not to swim due to the “Rip ” there.

1. Define (if you can!).

2. Define Rip .

3. Note this quote: “If you’re looking out toward the water and you see the long- current coming from both the left and right, there’s probably a in front of you.” (Rob Holman, Oregon State University).

a. According to the Playa Grande beach photos themselves (not the sign), do you see clear and obvious evidence of a rip current there?

b. In other words, what kind of beach process MUST be present in order to conclude that a Rip Current exists there?

4. a. If there is no Rip Current at Playa Grande, what other wording might you use to warn potential swimmers here?

b. In other words, what is the term for the potentially dangerous seaward flow of water in the surf zone; and,

c. What fundamental of nature creates this flow?

Note that is IS dangerous to swim at this beach! They are not mistaken about that!