Ngày 7 tháng 8 năm 2014 What Is the Difference Between Currents, Waves & Tides? | eHow

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How Are Ocean Currents Created? W  hat Is the Difference Betw eenCurrents & Waves?

Waves

 A wave is a forward motion of energy in water. As the w ind blows across the ocean's surface,

it pushes on the water, causing it to ripple. A wave's size and speed depends on the wind's

strength, the length of its gusts and how far it blows. The greater these three are, the larger

the wave. Steady winds produce a series of waves called a wave train, where one wav e

follows another in the same direction. The energy moves forward through the water, but the

 water itself does not move forward. As a wave approaches land, the ocean floor affects its

shape and speed, causing it to become unstable before it finally pitches forward and breaks on

the shore.

Tides

 A tide is the daily rise and fall of ocean waters caused by the Earth's rotation and the moon's

gravitational pull. This gravitational pull causes the ocean w ater closest to the m oon to bulge

out from the Earth, creating a high tide. On the opposite side of the globe, the moon's

gravitational pull forms a second bulge of water, creating a second high tide. Low tides lay in

the shallow areas found halfway between the two high tides. A particular tide returns about

every 24 hours and 50 minutes.

Ocean Currents

Ocean currents are like highways or rivers of continuously moving water that travel great

distances. Large surface currents are primarily driven by year-round winds and flow 

horizontally across the ocean's surface, spinning in large loops called gyres that rotate

clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere.

Subsurface currents may move vertically and are caused when cold or very salty water,

 which is denser, sinks below w arm or less-salty w ater, which is less dense.

Coastal Currents

Some currents occur only along the coast, and are caused by wave and tidal action. After a

 wave breaks on the beach, momentum carries water across the sand, and an undertow 

current returns it to the ocean. Longshore currents occur when waves strike the beach at an

What Is the Difference BetweenCurrents, Waves & Tides?

Currents, waves and tides drive the sea. While all three   contain  the

energy of motion, the factors and forces behind that motion vary,

 from atmospheric conditions to the Earth's rotation and the moon's

gravitational pull. These forces push and pull at the sea, offeri ng a

humbling reminder of the awesome power of nature.

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