1 00:00:00,520 --> 00:00:03,840 Speaker 1: Welcome to Brainstuff from house stuff Works dot com where 2 00:00:03,840 --> 00:00:15,640 Speaker 1: smart happens. Hi'm Marshall Brain with today's question, why are 3 00:00:15,640 --> 00:00:18,760 Speaker 1: the waves on the West coast of the United States 4 00:00:18,840 --> 00:00:21,440 Speaker 1: bigger and better than the waves on the East coast 5 00:00:21,520 --> 00:00:25,000 Speaker 1: of the United States. Some of the best surfing spots 6 00:00:25,000 --> 00:00:28,320 Speaker 1: in the world are located along the United States West 7 00:00:28,360 --> 00:00:31,640 Speaker 1: coast and in Hawaii, and the reason is simple. It's 8 00:00:31,680 --> 00:00:35,080 Speaker 1: the waves. But why are the waves on the West 9 00:00:35,120 --> 00:00:38,239 Speaker 1: coast bigger than those on the East coast. There are 10 00:00:38,360 --> 00:00:42,559 Speaker 1: three primary factors that determine a wave's height, First, the 11 00:00:42,640 --> 00:00:47,400 Speaker 1: prevailing winds, second, the continental shelf, and third, something called 12 00:00:47,440 --> 00:00:51,640 Speaker 1: the ocean fetch wind plays a big factor in wave height. 13 00:00:51,760 --> 00:00:54,560 Speaker 1: The important thing to remember about waves is that the 14 00:00:54,600 --> 00:00:58,160 Speaker 1: water isn't moving. The energy from the wind is moving 15 00:00:58,280 --> 00:01:01,720 Speaker 1: through the water. On the West coast, the prevailing winds 16 00:01:01,760 --> 00:01:05,200 Speaker 1: are behind the waves, which increases the waves energy. On 17 00:01:05,240 --> 00:01:08,240 Speaker 1: the East coast, the prevailing winds tend to blow against 18 00:01:08,319 --> 00:01:12,600 Speaker 1: the incoming waves, decreasing the waves energy. So obviously this 19 00:01:12,640 --> 00:01:15,640 Speaker 1: alone is gonna tend to make West Coast waves bigger 20 00:01:15,640 --> 00:01:19,639 Speaker 1: and better. Then there's the continental shelf on each coast 21 00:01:19,640 --> 00:01:22,959 Speaker 1: of the United states there is a continental shelf. To 22 00:01:23,120 --> 00:01:27,119 Speaker 1: understand the continental shelf, let's imagine that the ocean dried up. 23 00:01:27,440 --> 00:01:30,080 Speaker 1: The land under the water looks a bit like the 24 00:01:30,240 --> 00:01:34,360 Speaker 1: Grand Canyon, with cliffs and valleys, plateaus and ridges. On 25 00:01:34,400 --> 00:01:38,600 Speaker 1: the west coast, if you walked out onto the continental shelf, 26 00:01:38,640 --> 00:01:41,520 Speaker 1: you would notice that the shelf, the area between the 27 00:01:41,560 --> 00:01:45,479 Speaker 1: beach and where the drop off begins, is narrower. This 28 00:01:45,560 --> 00:01:48,200 Speaker 1: means that you have less sand to walk on before 29 00:01:48,200 --> 00:01:52,080 Speaker 1: the ocean's floor drops off steeply like a cliff. On 30 00:01:52,160 --> 00:01:55,520 Speaker 1: the east coast, the shelf is much broader. There's more 31 00:01:55,640 --> 00:01:59,280 Speaker 1: sand to walk on. As the shelf drops gradually like 32 00:01:59,400 --> 00:02:01,920 Speaker 1: a really long ramp that you might see it an airport, 33 00:02:02,040 --> 00:02:05,840 Speaker 1: parking lot or something like that. As the wave moves inland, 34 00:02:05,920 --> 00:02:08,680 Speaker 1: it hits the upward slope of the continental shelf. On 35 00:02:08,720 --> 00:02:12,400 Speaker 1: the east coast, the friction causes the water to slow down, 36 00:02:12,680 --> 00:02:16,720 Speaker 1: so the wave gradually collapses on itself. On the west coast, 37 00:02:16,800 --> 00:02:20,200 Speaker 1: the shelf rises suddenly near the coast, so the waves 38 00:02:20,240 --> 00:02:24,280 Speaker 1: are much larger when they crash into the coastline the water, 39 00:02:24,480 --> 00:02:27,400 Speaker 1: and thus the wave hasn't been slowed down by the 40 00:02:27,440 --> 00:02:30,920 Speaker 1: extended friction of the ramp of the East coast shelf. 41 00:02:31,400 --> 00:02:35,120 Speaker 1: Then there's this fetch thing. The Pacific Ocean on the 42 00:02:35,120 --> 00:02:39,080 Speaker 1: West coast has a greater expanse than the Atlantic Ocean 43 00:02:39,120 --> 00:02:42,800 Speaker 1: on the East coast. This means that the fetch, or 44 00:02:42,960 --> 00:02:45,960 Speaker 1: the distance over which the wind blows, is greater on 45 00:02:46,000 --> 00:02:48,840 Speaker 1: the West coast than on the East coast. In this case, 46 00:02:49,080 --> 00:02:51,360 Speaker 1: you can think of a wave as a snowball. The 47 00:02:51,440 --> 00:02:54,560 Speaker 1: farther you roll your snowball along in the snow, the 48 00:02:54,600 --> 00:02:58,480 Speaker 1: bigger it gets. West Coast waves tend to start way 49 00:02:58,680 --> 00:03:01,280 Speaker 1: way out in the Pacific Ocean, so they have a 50 00:03:01,320 --> 00:03:04,519 Speaker 1: greater distance to travel before they hit the shore, more 51 00:03:04,600 --> 00:03:08,880 Speaker 1: time to grow in size and length. Dr Ernie Knowles, 52 00:03:08,960 --> 00:03:13,280 Speaker 1: who's an associate professor of oceanography at NC State University, 53 00:03:13,440 --> 00:03:16,400 Speaker 1: can help us put all this together. He says the 54 00:03:16,600 --> 00:03:19,320 Speaker 1: steep shelf on the West coast would cause a more 55 00:03:19,400 --> 00:03:23,040 Speaker 1: abrupt build up of the shoaling wave, so waves would 56 00:03:23,040 --> 00:03:26,680 Speaker 1: be steeper when they break. But the much longer fetch 57 00:03:26,960 --> 00:03:30,280 Speaker 1: in the Pacific Ocean allows the waves to receive more 58 00:03:30,360 --> 00:03:34,160 Speaker 1: wind energy and so they grow larger. The swell arriving 59 00:03:34,200 --> 00:03:36,840 Speaker 1: on the West coast has periods in the range of 60 00:03:36,920 --> 00:03:40,840 Speaker 1: ten to seventeen seconds. Those are quite long waves, while 61 00:03:40,880 --> 00:03:44,840 Speaker 1: the East Coast swell is more like six to ten seconds. 62 00:03:45,160 --> 00:03:47,320 Speaker 1: What this all means is that if you're looking for good, 63 00:03:47,400 --> 00:03:50,520 Speaker 1: consistent waves, you need to be on the West coast 64 00:03:51,160 --> 00:03:53,320 Speaker 1: or on the East coast. You can wait for a 65 00:03:53,360 --> 00:03:56,320 Speaker 1: good hurricane to come along and really juice things up. 66 00:03:58,120 --> 00:04:00,600 Speaker 1: For more on this and thousands of other top visit 67 00:04:00,680 --> 00:04:05,880 Speaker 1: how stuff works dot com.