The Daring Book for Girls - Andrea J. Buchanan [74]
Tide charts show the moon phases because tides are caused by the pull of the moon’s gravity—and the sun’s gravity—on earth’s water. It’s an awe-inspiring concept that the moon’s pull—even at 239,000 miles away—is so strong that it can control our ocean waters. Next time you are at the seashore, with the waves lapping at your feet, you can observe the power of the moon.
More practically, tide charts list moon phases because it matters when you go fishing. High tides are higher during the new moon and the full moon. These are called spring tides. People who fish don’t much like spring tides—the water level is higher, and silt and sand from the bottom churn up and make the water murky. The result: Fish can’t see the bait on your line, and that’s no good if you’re trying to catch them. Some people will plan their fishing trips way in advance using the moon phases of tide charts, knowing to avoid the few days around new and full moon.
The opposite of high water spring tides are neap tides. They happen during the first and third quarters, when the moon waxes and wanes. There’s less water at high tide, and slightly less current.
There are two more moon trivia words you’ll want to know: a crescent moon is anything less than half, and any phase slightly-more-thanhalf to just-under-whole is a gibbous moon.
CRABBING: A CAPE COD TIDE CHART
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Date Day Time Height Time Height Time Height Time Height
7/10/07 Mon 5:18 AM 0.0 L 11:10 AM 2.1 H 5:09 PM 0.4 L 11:24 PM 3.1 H
The next chart shows low tide, which makes it helpful for crabbing and beachcombing. The initial Time column lists the first tide after midnight, no matter whether it’s low or high. Set your alarm clock, because that first tide comes in at 5:18 in the morning. The next column, Height, tells that the height of the water is 0.0, or average water level, and that the tide is L, or low. If you’re not an early riser, look for the second low tide of the day. Reading from left to right, you’ll see a high tide at 11:10 A.M., and then another low tide at 5:09 P.M. That’s the one you want.
At 4:00, then, head for the beach. The hours just before and after low tide are especially good for beachcombing and crabbing. Low tide is also a good time to see birds along the shore. They’ll be there picking at small animals and crabs that were left on the beach after the water receded.
SURFING: A COSTA RICAN TIDE CHART
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This chart from Nosara, on the Pacific coast of Costa Rica shows the tides in 24-hour time, which is used throughout the world, especially in non-English-speaking nations. (In the United States, 24-hour time is called Military Time, since that’s where it’s most often used.)
Hours 13-24 are equivalent to 1 P.M.-12 A.M. on the 12-hour clock, so to convert, just subtract 12. Thus high tide at 16:13 is 4:13 P.M., and low tide at 22:21 is 10:21 P.M.
Date Day High Time/Height Low Time/Height High Time/Height Low Time/Height
February 19, 2007 Monday 03:49/ 9.56 ft. 09:55/ -1.01 ft. 16:13/10.05 ft. 22:217-0.96 ft.
Globe-trotting surfers, even American ones, must get used to 24-hour time so they can easily read the tide charts as they travel across continents, surfboard under arm, seeking the perfect wave. This chart does a great job of showing how high the waves will swell. For surfing, the combination of tide, wind, and swell determine whether any given surf spot, or break, will have rideable waves at any given hour.
For example, a reef break means the waves are created (or break) when incoming water hits a reef that comes up from the ocean floor. At low tide, a reef break may give an excellent ride, on fast, steep waves. At high tide, however, the water may be so deep that it does not make strong impact with the reef, and this results in barely any wave to ride at all.
On the other hand, a beach break means waves form off large sandbars underwater. Often a higher tide is best for these surf spots, because they need the force of a lot of water rushing over the sandbars to make long, rounded waves.
BOATING: A CALIFORNIA TIDE CHART