Waves, Tides and Currents - How do they work?
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To swimmers and surfers, the ocean is an aquatic playground. However, to
witnesses of a destructive tsunami wave, the ocean can also be a source of
potential danger to lives and property.|
Waves, tides and currents are what drive the sea. Waves we associate with the beach and having fun. Tides signal the stages of the moon and the time of day. Currents provide passage for international boats that bring us food and goods from far away lands. All three contain energy of motion and potential energy. The slightest change in any of these effects us in many more ways than you think.
Tsunamis, often erroneously called tidal waves, result when underwater earthquakes and volcanic eruptions disrupt the water's surface. Most other waves are caused by wind driving against water. When a breeze of two knots or less blows over calm water, small ripples form and grow as the wind speed increases until whitecaps, comprised of millions of tiny air bubbles, appear in the breaking waves. Waves may travel thousands of miles before rolling ashore and dissolving as surf.
A wave's size and shape reveals its origins. A steep, choppy wave out at sea is fairly young and was probably formed by a local storm. Slow, steady waves near shore which rear high crests, and plunge into foam come from far away, possibly another hemisphere.
No two waves are identical, but they all share common traits. Every wave, from a tiny ripple to a huge tsunami, has a measurable wave height, the vertical distance from its crest (high point) to its trough (low point). Wind speed, duration, and fetch (the distance it blows over open water) determine how high a wave grows. The maximum height in feet is usually one half or less the wind speed in miles per hour. Wave height decreases gradually as the wind dies and the wave approaches shore. When it touches bottom, it slows, the back overtakes the front, forcing it into a peak, curves forward, and dissolves into a tumbling rush of foam and water called a breaker.
Spilling breakers, a favorite with surfers, are turbulent water with foam cascading down the front. They form on gently sloping or flat shores and roll great distances before breaking.
Plunging breakers form when the bottom rises abruptly toward the shore. As the crest folds over, it creates a large air pocket, followed by a smooth splash-up. Experienced surfers can sometimes crouch under the falling crest and lock themselves inside the air tube. However, plungers can hurl 135 pound boulders more than 100 feet in the air and can damage buildings 100 - 300 feet above the sea surface.
Waves are fun on a hot summer's day, but they are also a constant reminder of the sea's awe-inspiring power.
How are waves energy?
What provides the energy?
What determines the size of the wave?
Where are the largest waves found?
The Effect Of The Sun And Moon On Tides
What does the pull of the sun and moon do to the oceans?
Where Does Water Go At Low Tide?
Spring Tides And Neap Tides
Tides Around The World
Just like waves, oceans currents are always moving about.
Doesn't the wind cause ocean currents?
Both winds are a result of warm air from the tropics moving to the poles and incorporating the rotation of Earth into their movement. In the Northern Hemisphere, they move clockwise. In the Southern Hemisphere, they move counter-clockwise.
Doesn't temperature cause currents, too?
The mixing and warming of water cause the currents. As these currents move around the world, they also help replenish the oxygen in the water.
What else causes currents?
What is the Gulf Stream?
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