The surf zone

THE SURF ZONE
A photo tour of selected beaches to
illustrate:
• Plunging and spilling breakers
• Longshore currents
• Rip currents
• Undertow
Shoreline Community College
Oceanography 101
Linda Khandro

HOW TO PROCEED

• First of all, study ALL the pictures and videos of the surf and beach
slope formations in this Power Point. Take your time and enjoy!
• STOP when you get to (about) slide 76 with the instructions. This
slide and the ones following it, are also attached to the EX6
Assignment page in our Blackboard Week 6 folder. Download and
save the file from Blackboard to your hard drive, labeling as usual:
lastname_ex6.doc.
• Print that file for easy reference as you go through these pictures
and videos again.
• Answer all the questions on your new file.
• When you come to question D, about “rip tides”, rip currents, and
longshore currents, BE SURE to go back to slide 74. There you must
open the links to see and hear about the formation of rip currents
from longshore currents.
• Finish answering the questions on your file and attach to the
Blackboard Assignment page.

• You’re done! Now watch out for rip currents and undertow!

Some
beaches of
New
Zealand…

Some beaches of Baja, Mexico:
The west side is on the Pacific
Ocean, the south point of Baja is
between the Pacific and the Sea
of Cortez, and the east side is on
the Sea of Cortez.
Some of these slides are videos. Mouse
over the slide until the white box shows
up at the bottom. Click on the arrow at
the bottom left side.

Beach at El Pozo
Hondo, near
Todos Santos
(west side)…

Los Cerritos
beach, near
Todos Santos
(west side)…

Beach at Playa
Grande, near
Cabo San Lucas,
south point of
Baja

Beach at San
Jose del Cabo,
south point of
Baja…

Beach at Cabo
Pulmo, east side
of Baja (Sea of
Cortez)…

Some beaches of Yucatan,
Mexico: Puerto Morelos and
Cancun are both on the Caribbean
side of the Yucatan Peninsula.

Some of these slides are videos. Mouse
over the slide until the white box shows up
at the bottom. Click on the arrow at the
bottom left side.

Puerto Morelos
beach, with the
Mesoamerican
Reef offshore
(white surf)…

Some beaches
of Cape Cod,
Massachusetts
…
.

THE SURF ZONE
Some important points:
1. There are 3 main types of surf, with surging, plunging
and spilling breakers, all of which form in response to
various factors of the beach slope, including the
steepness of the slope. We are discussing only plunging
and spilling waves, or breakers, here.
2. A steeply sloping beach face can create a strong
undertow.
3. Converging longshore currents can create rip currents.
4. The dangers created by rip currents and undertow are
real, but are not the same.

http://oregonstate.edu/dept/ncs/newsarc
h/2007/Jul07/ripcurrents.html

“If you’re looking out toward the water
and you see the long-shore current coming
from both the left and right, there’s
probably a rip current in front of you.”

http://www.nytimes.com/interactive/200
9/01/06/science/20090106-
sandslide/index.html

INSRUCTIONS FOR THE EXERCISE:

Now download and print the Blackboard EX6
Assignment page! If you already have it, you’re ready to
go back to the beaches slides above, then answer the
questions on the Assignment page.

Use your Textbook pages 210-211 and the Glossary
pages 420 & 423 for further reference to plunging and
spilling breakers.

The following 7 slides just re-state the questions. Type
your answers onto the page you have labeled
lastname_ex6.doc.

A. Plunging Breakers
1. Which of the beaches illustrate, for the
most part, “plunging” breakers? Name the
beaches as they are labeled on the slides.

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
1. Which of the beaches illustrate, for the
most part, “spilling” breakers? Name the
beaches as they are labeled on the slides.

2. What is 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?

Reef Breakers: 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? If you can’t tell from
the photos, consider that the reef has a
fairly steep slope on the seaward side.

D. Rip (tides or currents?) At Playa
Grande beach, you will see a red warning
sign (previous slide) advising guests not to
swim due to the Rip Tide there.

1. Define Rip Tide (if you can!).

2. Define Rip Current. What kind of beach
process must be present for a rip current
to form? If in doubt, see Slide 78 again.

3. According to the beach photos
themselves (not the sign), do you see
evidence of a Rip Current at Playa Grande?

4. If there is no Rip Current at Playa
Grande, how else would you warn
potential swimmers here? Look again at
the seaward flow of water after the surf
breaks; look at the slope of the beach face
and think about the fundamental force of
nature which creates that flow of water.

5. What name (or names) do we give
to that seaward flow of water?

6. What is the fundamental force of
nature that creates the danger at this
beach?

The surf zone

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