MadSci Network: Earth Sciences

Re: How do ocean waves form?

Date: Fri Mar 24 10:17:29 2000
Posted By: Paul Odgren, Instructor, Cell Biology, University of Massachusetts Medical School (Dept. of Cell Biology)
Area of science: Earth Sciences
ID: 947205727.Es

Hi, JPR,
        I just found your question waiting in line, and I hope you've been 
exploring it on your own since you submitted it. It's a very good question, 
and I hope my answer helps.
	The simple answer - the wind causes waves (once in a while, of 
course, there is an earthquake under the ocean that causes a "tidal wave", 
or tsunami, as the Japanese call them), but all those waves that crash 
endlessly on the beaches of the world, day in and day out, year after year, 
are caused by winds. When you're in boat in the ocean far from land, the 
waves come from every direction, because they can travel for many, many 
miles, and the wind blows in different directions in different areas and 
often changes from day to day. When the waves get to shallow water near the 
shore, there is friction between the waves and the sea bottom. The effect 
of that friction is to turn the waves so that come straighter in toward the 
shore. If you're standing on a lookout point above the shore, you can often 
see this effect. 
	Now imagine what's happening on a day when the waves are coming in 
toward you even though the wind is blowing out toward the sea from the 
shore. The waves breaking on shore got started someplace, possibly hundreds 
of miles away, where the wind direction was more or less blowing toward the 
shore, and they have continued despite having the wind now blowing at them. 
At the same time, there are new waves being formed by the wind you feel, 
and they will build up and head away from the shore. At some time in 
next several days, they may be breaking on a beach on the other side of the 
ocean, and cause some curious kid to wonder where they came from. Now you 
could answer, "They started one day right off this beach."

Paul Odgren, Ph.D.
Cell Biology
University of Massachusetts Medical School

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