WEBVTT - Why are West Coast waves bigger than East Coast waves?

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<v Speaker 1>Welcome to Brainstuff from house stuff Works dot com where

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<v Speaker 1>smart happens. Hi'm Marshall Brain with today's question, why are

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<v Speaker 1>the waves on the West coast of the United States

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<v Speaker 1>bigger and better than the waves on the East coast

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<v Speaker 1>of the United States. Some of the best surfing spots

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<v Speaker 1>in the world are located along the United States West

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<v Speaker 1>coast and in Hawaii, and the reason is simple. It's

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<v Speaker 1>the waves. But why are the waves on the West

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<v Speaker 1>coast bigger than those on the East coast. There are

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<v Speaker 1>three primary factors that determine a wave's height, First, the

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<v Speaker 1>prevailing winds, second, the continental shelf, and third, something called

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<v Speaker 1>the ocean fetch wind plays a big factor in wave height.

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<v Speaker 1>The important thing to remember about waves is that the

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<v Speaker 1>water isn't moving. The energy from the wind is moving

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<v Speaker 1>through the water. On the West coast, the prevailing winds

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<v Speaker 1>are behind the waves, which increases the waves energy. On

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<v Speaker 1>the East coast, the prevailing winds tend to blow against

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<v Speaker 1>the incoming waves, decreasing the waves energy. So obviously this

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<v Speaker 1>alone is gonna tend to make West Coast waves bigger

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<v Speaker 1>and better. Then there's the continental shelf on each coast

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<v Speaker 1>of the United states there is a continental shelf. To

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<v Speaker 1>understand the continental shelf, let's imagine that the ocean dried up.

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<v Speaker 1>The land under the water looks a bit like the

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<v Speaker 1>Grand Canyon, with cliffs and valleys, plateaus and ridges. On

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<v Speaker 1>the west coast, if you walked out onto the continental shelf,

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<v Speaker 1>you would notice that the shelf, the area between the

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<v Speaker 1>beach and where the drop off begins, is narrower. This

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<v Speaker 1>means that you have less sand to walk on before

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<v Speaker 1>the ocean's floor drops off steeply like a cliff. On

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<v Speaker 1>the east coast, the shelf is much broader. There's more

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<v Speaker 1>sand to walk on. As the shelf drops gradually like

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<v Speaker 1>a really long ramp that you might see it an airport,

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<v Speaker 1>parking lot or something like that. As the wave moves inland,

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<v Speaker 1>it hits the upward slope of the continental shelf. On

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<v Speaker 1>the east coast, the friction causes the water to slow down,

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<v Speaker 1>so the wave gradually collapses on itself. On the west coast,

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<v Speaker 1>the shelf rises suddenly near the coast, so the waves

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<v Speaker 1>are much larger when they crash into the coastline the water,

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<v Speaker 1>and thus the wave hasn't been slowed down by the

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<v Speaker 1>extended friction of the ramp of the East coast shelf.

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<v Speaker 1>Then there's this fetch thing. The Pacific Ocean on the

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<v Speaker 1>West coast has a greater expanse than the Atlantic Ocean

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<v Speaker 1>on the East coast. This means that the fetch, or

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<v Speaker 1>the distance over which the wind blows, is greater on

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<v Speaker 1>the West coast than on the East coast. In this case,

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<v Speaker 1>you can think of a wave as a snowball. The

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<v Speaker 1>farther you roll your snowball along in the snow, the

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<v Speaker 1>bigger it gets. West Coast waves tend to start way

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<v Speaker 1>way out in the Pacific Ocean, so they have a

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<v Speaker 1>greater distance to travel before they hit the shore, more

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<v Speaker 1>time to grow in size and length. Dr Ernie Knowles,

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<v Speaker 1>who's an associate professor of oceanography at NC State University,

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<v Speaker 1>can help us put all this together. He says the

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<v Speaker 1>steep shelf on the West coast would cause a more

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<v Speaker 1>abrupt build up of the shoaling wave, so waves would

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<v Speaker 1>be steeper when they break. But the much longer fetch

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<v Speaker 1>in the Pacific Ocean allows the waves to receive more

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<v Speaker 1>wind energy and so they grow larger. The swell arriving

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<v Speaker 1>on the West coast has periods in the range of

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<v Speaker 1>ten to seventeen seconds. Those are quite long waves, while

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<v Speaker 1>the East Coast swell is more like six to ten seconds.

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<v Speaker 1>What this all means is that if you're looking for good,

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<v Speaker 1>consistent waves, you need to be on the West coast

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<v Speaker 1>or on the East coast. You can wait for a

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<v Speaker 1>good hurricane to come along and really juice things up.

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<v Speaker 1>For more on this and thousands of other top visit

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<v Speaker 1>how stuff works dot com.