earth science 23

earth science 23 - Lab on Waves, Currents, Tides, and Sea...

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Lab on Waves, Currents, Tides, and Sea Level Changes Waves Waves transfer energy from one place to another. Waves in the oceans (or large lakes) are caused by wind blowing over the surface of the water . The size of a wave is determined by how far, how fast and how long the wind blows. A gentle breeze forms patches of tiny ripples on the surface of the water. Strong, steady winds over long distances create large waves. But even if you feel no wind at all, you may seer large waves caused by distant storms. All waves have certain characteristics in common. The highest point of a wave is called the crest . The lowest point of a wave is called the trough . Wavelength is the horizontal distance between two adjacent wave crests . Wave height - the vertical distance from the bottom of a trough to the top of a crest The number of waves that pass a given point in one second is the wave's frequency . Diagram illustrating the parts of a wave. Image courtesy of Office of Naval Research. Or click here to see a diagram showing parts of a wave . Things that float In the open ocean bob up and down when a wave passes, instead of moving along with the wave. This is because the waves are caused by energy travelling through water. Waves do not move the water along with them. As a wave arrives it lifts water particles. The water particles travel forward, then down and
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Each water particle completes a circle . Circling movements of water particles near the surface set off smaller circling movements below them. The water particle moves in a vertical circle as the wave passes. The particle moves forward with the wave crest, and backward with the wave trough. Image courtesy of Office of Naval Research. Click here to see diagram of circular motion of water particles decreasing with depth, and waves approaching a shore. From Water on the Move, Museum of Science . Wave base (= 1/2 of the wavelength ) - there is negligible water movement from waves below this depth. Wave refraction - waves bend as they enter shallow water from the open ocean, due to velocity change. When wave base touches bottom, the waves slow down . Because the wave approaches the shore at an angle, wave base on one end drags bottom before the other end . This causes bending or refraction of the wave. Waves bend to become more parallel with the coast . Longshore drift (or longshore transport); also called beach drift. Sediment is transported along the beach by the waves. Waves rush onto the beach at a slight angle, but they rush straight back out to sea because of gravity. Because of this, sediment in the surf zone is transported along the beach in a zig-zag pattern. It is referred to as a longshore current. Longshore drift of sand on the beach face and by a longshore current within
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This note was uploaded on 04/19/2011 for the course ERTH 100 taught by Professor Jerryw.kousen during the Spring '11 term at Vincennes.

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earth science 23 - Lab on Waves, Currents, Tides, and Sea...

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