Why are West Coast waves bigger than East Coast waves?

The West Coast of the United States seems to produce bigger, more impressive waves than the East Coast. But why? In this episode, Marshall explains the various factors that make West Coast waves bigger and better.

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Episode Transcript

Speaker 1 (00:00):
Welcome to Brainstuff from house stuff Works dot com where
smart happens. Hi'm Marshall Brain with today's question, why are
the waves on the West coast of the United States
bigger and better than the waves on the East coast

(00:21):
of the United States. Some of the best surfing spots
in the world are located along the United States West
coast and in Hawaii, and the reason is simple. It's
the waves. But why are the waves on the West
coast bigger than those on the East coast. There are
three primary factors that determine a wave's height, First, the

(00:42):
prevailing winds, second, the continental shelf, and third, something called
the ocean fetch wind plays a big factor in wave height.
The important thing to remember about waves is that the
water isn't moving. The energy from the wind is moving
through the water. On the West coast, the prevailing winds
are behind the waves, which increases the waves energy. On

(01:05):
the East coast, the prevailing winds tend to blow against
the incoming waves, decreasing the waves energy. So obviously this
alone is gonna tend to make West Coast waves bigger
and better. Then there's the continental shelf on each coast
of the United states there is a continental shelf. To
understand the continental shelf, let's imagine that the ocean dried up.

(01:27):
The land under the water looks a bit like the
Grand Canyon, with cliffs and valleys, plateaus and ridges. On
the west coast, if you walked out onto the continental shelf,
you would notice that the shelf, the area between the
beach and where the drop off begins, is narrower. This
means that you have less sand to walk on before

(01:48):
the ocean's floor drops off steeply like a cliff. On
the east coast, the shelf is much broader. There's more
sand to walk on. As the shelf drops gradually like
a really long ramp that you might see it an airport,
parking lot or something like that. As the wave moves inland,
it hits the upward slope of the continental shelf. On

(02:08):
the east coast, the friction causes the water to slow down,
so the wave gradually collapses on itself. On the west coast,
the shelf rises suddenly near the coast, so the waves
are much larger when they crash into the coastline the water,
and thus the wave hasn't been slowed down by the
extended friction of the ramp of the East coast shelf.

(02:31):
Then there's this fetch thing. The Pacific Ocean on the
West coast has a greater expanse than the Atlantic Ocean
on the East coast. This means that the fetch, or
the distance over which the wind blows, is greater on
the West coast than on the East coast. In this case,
you can think of a wave as a snowball. The

(02:51):
farther you roll your snowball along in the snow, the
bigger it gets. West Coast waves tend to start way
way out in the Pacific Ocean, so they have a
greater distance to travel before they hit the shore, more
time to grow in size and length. Dr Ernie Knowles,
who's an associate professor of oceanography at NC State University,

(03:13):
can help us put all this together. He says the
steep shelf on the West coast would cause a more
abrupt build up of the shoaling wave, so waves would
be steeper when they break. But the much longer fetch
in the Pacific Ocean allows the waves to receive more
wind energy and so they grow larger. The swell arriving

(03:34):
on the West coast has periods in the range of
ten to seventeen seconds. Those are quite long waves, while
the East Coast swell is more like six to ten seconds.
What this all means is that if you're looking for good,
consistent waves, you need to be on the West coast
or on the East coast. You can wait for a
good hurricane to come along and really juice things up.

(03:58):
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