Oceanography Last Modified 2002-October-23 Beaches Steep beach Monastery Beach (just south of Carmel, California) The energy is used in one huge plunging breaker right on shore (this is very powerful and deceptive surf). The sand granularity is course (like rock salt from a water softener). Illustration: Steep Beach Shallow beach Del Monte Beach (just north of Monterey, California) The energy is spread over two or three sets of breakers over a wide area. The sand granularity is fine (a little finer than table sugar). Illustration: Shallow Beach Rocky beach The outside north wall at Salt Point State Park or Stewart's Point (just south of Carmel, Ca.) Illustration: Rocky Beach Be very careful of the slippery rocks. Breakers Swells slow down when they "feel" the bottom, causing them to build in height until the topple becoming breakers. If you look at the surf line and see an 8 foot [2.4m] breaker, the water is about 6 feet [1.9m] deep where the breaker is breaking. (approximate ratio = 1.3 breaker height to depth) Spilling breaker Illustration: Spilling Breaker Slow breaker, feels the bottom early (shallow angle beach). Breaks over a long distance, dispelling energy as it goes along. The water from the crest does not have enough speed and spills down the face. (creating white water on the face.) Plunging breaker Illustration: Plunging Breaker Fast breaker, feels the bottom late (steep beach or step up to a reef). Builds and breaks in a very short distance, dispelling all it energy in one place. The water from the crest has enough speed and shoots out over the face of wave plunging into the bottom of the trough forming a tube. Offshore breaker Illustration: Offshore Breaker Waves Energy travelling through the water. (The water itself doesn't move much, see Surge) Illustration: Wave Nominclature Swells Long rolling waves; generated a long way away. (more than 200 miles [322km]) Caused by wind blowing steadily in one direction over a long distance (fetch). Most of our swells come from the Gulf of Alaska and Northwest Pacific. (A long fetch = Big Swells; A strong wind = Swell that are close together) Illustration: Swells vs Surge Surge The back and forth motion of the water caused by swells. The affects of surge gets smaller and smaller the deeper you go. A general rule: the longer the swell the deeper the surge will be felt. When swimming, use the surge to your advantage. (i.e., if the surge is going the way you want to go, swim with it; if the surge is against you, put your hand down and hold on to the bottom. [this uses very little energy]) Wind Chop (Seas) Short choppy waves; generated locally (within 200 miles [322km]). Seas are chop on top of the swells and usually come up in the afternoon (when the wind blows on shore). Currents Longshore Current The surf pushes water (and sand, etc.) in the direction it's going causing a longshore current. Illustration: Longshore Current Tidal Current Caused by the relative difference of water levels between two bodies of water separated by a narrow channel. (For example, the Ocean and the Bay below.) When diving in locations with strong tidal currents (the Puget Sound), plan your dives around the slack tides. Illustration: Tidal Current Rip Current Caused by water flowing out a low spot on the beach. Surf knocked down where the rip goes through. Use the rip as an easy route thru the surf line. If you're caught in a rip, swim perpendicular (90 degrees) to the rip. Don't try to swim agains the rip, the ocean doesn't get tired. Illustration: Rip Current The California Current This is the major oceanic current that flows from about the US/Canada border down the the west coast of North America to the tip of Baja California. Tides The biggest influences on the tides are the moon and the sun. 27 days, 7 hrs, 43 min, and 11.47 sec for one lunar orbit around the earth. 29 days, 12 hrs, 44 min, and 2.78 sec for the moon to go from full moon to full moon (a lunar month), the difference is because of the earth orbiting the sun. Approximately 24 hrs, 50min per tide cycle. Spring tide The sun and moon pull together. (Full Moon/New Moon) Neap tide The sun and moon pull at 90° to the earth. (Waxing Quarter/Waning Quarter) Illustration: Tides Ripples in the Sand Ripples from a current These ripples are generally small, usually less than a hand's width in height and about two hand widths in length. Illustration: Ripples from a current Ripples from the surge These ripples are symetrical, run parallel to the beach, and can get quite large depending on the strength of the surge. (Monastry Beach has 12 to 15 inch [30 to 35cm] high ripples, spaced about three feet [1m] crest to crest.) Illustration: Ripples from the surge © 1997, 2002 Chris Simmons. All rights reserved. Last Modified 2002-October-23