Speaker 1: Welcome to Brainstuff from house stuff Works dot com where
Speaker 1: smart happens. Hi'm Marshall Brain with today's question, why are
Speaker 1: the waves on the West coast of the United States
Speaker 1: bigger and better than the waves on the East coast
Speaker 1: of the United States. Some of the best surfing spots
Speaker 1: in the world are located along the United States West
Speaker 1: coast and in Hawaii, and the reason is simple. It's
Speaker 1: the waves. But why are the waves on the West
Speaker 1: coast bigger than those on the East coast. There are
Speaker 1: three primary factors that determine a wave's height, First, the
Speaker 1: prevailing winds, second, the continental shelf, and third, something called
Speaker 1: the ocean fetch wind plays a big factor in wave height.
Speaker 1: The important thing to remember about waves is that the
Speaker 1: water isn't moving. The energy from the wind is moving
Speaker 1: through the water. On the West coast, the prevailing winds
Speaker 1: are behind the waves, which increases the waves energy. On
Speaker 1: the East coast, the prevailing winds tend to blow against
Speaker 1: the incoming waves, decreasing the waves energy. So obviously this
Speaker 1: alone is gonna tend to make West Coast waves bigger
Speaker 1: and better. Then there's the continental shelf on each coast
Speaker 1: of the United states there is a continental shelf. To
Speaker 1: understand the continental shelf, let's imagine that the ocean dried up.
Speaker 1: The land under the water looks a bit like the
Speaker 1: Grand Canyon, with cliffs and valleys, plateaus and ridges. On
Speaker 1: the west coast, if you walked out onto the continental shelf,
Speaker 1: you would notice that the shelf, the area between the
Speaker 1: beach and where the drop off begins, is narrower. This
Speaker 1: means that you have less sand to walk on before
Speaker 1: the ocean's floor drops off steeply like a cliff. On
Speaker 1: the east coast, the shelf is much broader. There's more
Speaker 1: sand to walk on. As the shelf drops gradually like
Speaker 1: a really long ramp that you might see it an airport,
Speaker 1: parking lot or something like that. As the wave moves inland,
Speaker 1: it hits the upward slope of the continental shelf. On
Speaker 1: the east coast, the friction causes the water to slow down,
Speaker 1: so the wave gradually collapses on itself. On the west coast,
Speaker 1: the shelf rises suddenly near the coast, so the waves
Speaker 1: are much larger when they crash into the coastline the water,
Speaker 1: and thus the wave hasn't been slowed down by the
Speaker 1: extended friction of the ramp of the East coast shelf.
Speaker 1: Then there's this fetch thing. The Pacific Ocean on the
Speaker 1: West coast has a greater expanse than the Atlantic Ocean
Speaker 1: on the East coast. This means that the fetch, or
Speaker 1: the distance over which the wind blows, is greater on
Speaker 1: the West coast than on the East coast. In this case,
Speaker 1: you can think of a wave as a snowball. The
Speaker 1: farther you roll your snowball along in the snow, the
Speaker 1: bigger it gets. West Coast waves tend to start way
Speaker 1: way out in the Pacific Ocean, so they have a
Speaker 1: greater distance to travel before they hit the shore, more
Speaker 1: time to grow in size and length. Dr Ernie Knowles,
Speaker 1: who's an associate professor of oceanography at NC State University,
Speaker 1: can help us put all this together. He says the
Speaker 1: steep shelf on the West coast would cause a more
Speaker 1: abrupt build up of the shoaling wave, so waves would
Speaker 1: be steeper when they break. But the much longer fetch
Speaker 1: in the Pacific Ocean allows the waves to receive more
Speaker 1: wind energy and so they grow larger. The swell arriving
Speaker 1: on the West coast has periods in the range of
Speaker 1: ten to seventeen seconds. Those are quite long waves, while
Speaker 1: the East Coast swell is more like six to ten seconds.
Speaker 1: What this all means is that if you're looking for good,
Speaker 1: consistent waves, you need to be on the West coast
Speaker 1: or on the East coast. You can wait for a
Speaker 1: good hurricane to come along and really juice things up.
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