Oceanography 101 Linda Khandro, MAT Homework 9: the Surf Zone

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Oceanography 101 Linda Khandro, MAT Homework 9: The Surf Zone (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 Longshore Drift: 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 beaches on the blog illustrate, for the most part, “plunging” breakers? 2. Which of the beaches with plunging breakers clearly show(s) a steep beach 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. Reef 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 (tides 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 Tide” there. 1. Define Rip Tide (if you can!). 2. Define Rip Current. 3. Note this quote: “If you’re looking out toward the water and you see the longshore current coming from both the left and right, there’s probably a rip current 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 force of nature creates this flow? Note that is IS dangerous to swim at this beach! They are not mistaken about that! .

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