In this assignment, you’ll focus on three important wave behaviors

In this assignment, you’ll focus on three important wave behaviors: dispersion of deep water waves, and refraction and breaking of shallow water waves.  If these concepts are unfamiliar, I recommend that you review this brief wave tutorial before going on with the assignment.

In this assignment, you’ll focus on three important wave behaviors

Ocean Waves (15 points)

In this assignment, you’ll focus on three important wave behaviors: dispersion of deep water waves, and refraction and breaking of shallow water waves.  If these concepts are unfamiliar, I recommend that you review this brief wave tutorial before going on with the assignment.

PART A: Dispersion of deep water waves

California is world famous for surfing because the Pacific Ocean sends world-class swells our way most days of the year.  Where do these large swells come from?  Not from the gentle breezes that softly caress your cheek as you wander the beach—that’s for sure.  Those breezes make nothing bigger than little ripples.  Most of the big swells that surfers love to ride are made by large storms far out at sea.

A storm that thrashes up the ocean is like a wave factory.  As the waves move away from the storm, different sets of waves separate out from one another to form swells via the process of dispersion: the spreading out of waves as they travel at different speeds away from a storm.  The beautiful, smooth, evenly spaced swells that regularly roll in to the California coast represent energy put into the ocean surface from storms that may have occurred thousands of miles away!

To do this part of the assignment, watch the short video module below on wave dispersion and swell formation.

https://youtu.be/orLlhZw7OoQ

Next, keeping in mind the concepts and information in the video module above, look at the images and text at this link: large North Pacific storm.

Clearly label your answers (A1, A2, etc.) to the questions below:

A1.  Imagine a group of cars accelerating away from a stoplight at different speeds.  How is this similar to what I was explaining in the video module?

A2.  What is the connection between wave speed, wave period, wavelength, and wave dispersion?

A3.  In Image 1 at the “ large North Pacific storm” link, what is the expected height of the largest waves?

A4.  In Image 2, what is the connection between the wave period and where the waves are?  (Keep in mind that the storm occurred to the north, near Alaska, and the waves are spreading outward from there like ripples on a pond.)

A5.  Comparing Image 3 to Image 4, what is the difference in the wave period, and why is there a difference?  (Be sure to read the text that goes with each image.)

Part B: Refraction in shallow water waves: focus on Mavericks

Refraction is the process that causes waves to bend and change direction as they slow down in shallow water near the shore.  Refraction (among other things) creates the world-famous surfing waves at places such as Peahi (Jaws) on Maui, Todos Santos Island off Baja California, Cortes Bank west of San Diego, and Mavericks at Half Moon Bay south of San Francisco.  In this part of the assignment, you’l l take a close look at the Mavericks Wave.

To understand how wave refraction works, and why it creates the big waves at Mavericks, first watch the short video module on wave refraction below.  Be sure to watch the module before you go on to the next step; you won’t be able to fully answer the questions below if you skip ahead.

 https://youtu.be/G1FIBuybN78

Next, watch the 10-minute video below about Mavericks.

This excellent video explains the science behind the Mavericks wave!  NOTE: If you prefer, you can watch a higher resolution version of the video at this link:

http://science.kqed.org/quest/video/science-of-big-waves/

https://youtu.be/qv_nItHCZ_E

Using the concepts and information in BOTH of the videos above, answer the following questions.  Label your answers clearly (B1, B2, etc.).

B1.  As waves come from the open ocean into shallow water, they change from deep water waves into shallow water waves.  At what depth does this change occur, and what are the main effects (i.e. how do the waves change)?

B2.  How can refraction cause wave energy to be concentrated in one area, causing larger waves?  How can refraction cause wave energy to be dissipated in another area, causing smaller waves?

B3.  Where do the waves that break at Mavericks originate, and what time of year do these waves tend to form?

B4.  What three things do you need to get big waves? Explain each one briefly (one sentence).

B5.  Explain how and why the shape of the sea floor causes particularly big waves at Mavericks.  (Tip: describe the results of Cal State Monterey’s multi-beam sonar mapping of the sea floor, and relate your answer to B2 above.)

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