[Boerseun]

The Artificial Kid said:

Last year in India I saw an ocean beach that acted as quite a good reflector for small waves, bouncing them back and creating interesting interference with patterns, although the quickly got swamped by the prevailing shoreward wave action. This makes me think that the main reason waves seem to move shorewards is that the shore usually neither generates nor reflects waves. The ocean has a lot of wave potential and the shore is a wave sink.

Reflected waves are very rare, and depend on perfect conditions like flat waterbreaks, etc. But waves will not spontaneously form from land to see, because the waves need quite a distance to receive enough energy input from the wind to grow to sufficient proportions to rightly be called "waves". Standing on the beach with the land towards your back, you will not see waves forming to go out to the ocean - even with a relatively strong wind coming from the land - because the wind does not have enough of a distance to impart its energy upon the water. A distance into the sea, quite a few km's, you should start seeing waves being born going seeward - if the wind conditions are right.

I have seen waves hitting the beach from all sorts of crazy angles, but have never seen waves forming from the beach to go into the sea because of the distance issue. Which means that the waves don't always go towards the shore, the waves go in all directions and the shore just happens to be in the way. Leeward, of course, you will not find any waves - but that in itself should be no mystery.

[phision]

Becca, on 28 January 2007 - 06:46 AM, said:

this was a question on my A level physics exam and has puzzled me for years since then. can anybody help me with this?

Why do waves always seem to go towards the shore?

Ocean surface wave are generated on the surface of the water and propegate away from their origin(where they are created) until they reach the boundary of the body of water i.e. the shore, hence "always seem to go towards the shore".

[Knothead]

Boerseun, on 03 March 2007 - 07:16 PM, said:

Air tends to rise over land as the land is generally hotter than the ocean. Air tends to drop over the ocean as it cools down again. So there is a permanent cycle of cool air blowing in from the sea, to be heated over land, to rise, to circulate back over the sea again.

Waves are formed through wind action. The ocean wind generally blows from the cold ocean to the warm land, forming waves which looks as if they're always aiming for the land.

It all depends on the specific local weather system. You can even find waves running parallel to the shore if the wind conditions are such. What I wrote above was merely a generalisation.

This is called a sea breeze and a land breeze.

http://www.classzone...s1903page01.cfm

I can tell you that in open waters, the waves go which ever way the wind is blowing. Sometimes they go whichever way the wind was blowing yesterday and the day before at the same time. Meaning that they come from different directions. Boy is that uncomfortable.

[phision]

Knothead, on 16 December 2011 - 11:11 AM, said:

I can tell you that in open waters, the waves go which ever way the wind is blowing. Sometimes they go whichever way the wind was blowing yesterday and the day before at the same time. Meaning that they come from different directions. Boy is that uncomfortable.

Regardless of which way the wind blows, the waves are created at the surface of water and travel from there to the boundary of the water which is the shore. See #17 .

[esbo]

phision, on 15 December 2011 - 04:47 PM, said:

Why do waves always seem to go towards the shore?

Ocean surface wave are generated on the surface of the water and propegate away from their origin(where they are created) until they reach the boundary of the body of water i.e. the shore, hence "always seem to go towards the shore".

I tend to agree with this!!
I was puzzled by this somewhat, one thing which crossed my mind was that winds tend to be usually onshore, but
I amd pretty sure this is not always the case.

Certainly you would not expect a big wave to start off from the shore because they take time to build up.
Waves of course tend to go outward from there point of origin and there is no real point of origin for
a wave on the shore.
Every thing that move in the sea will generate outward waves, ie fish, ships, whales!!!
They all radiate outwards and will even go through each other, but ultimately always end up on the shore.


I think even if you have a strong off shore breeze that will generate mini-outwards waves, but they will
be small beans compared to the cumulative incoming waves.
What I think will happen is this case is you get a more 'choppy effect'.

It's an interesting question, one of those things you never really think about but just take for granted!!

[Under the Rose]

An interesting dialogue on wave action.

For a number of years, I lived close to Atlin Lake, B.C., which is a natural freshwater lake approximately 4 miles wide and 85 miles long, situated between mountains. Yes, the waves are always lapping at the shore, save on one of those very rare days of dead calm when the lake will be as flat and reflective as a mirror.

No wind, no waves, on inland lakes.

The wind is influenced by the mountains and the long narrow lake can really kick up if a North/South wind starts to blow. At such times the big waves are NOT headed to shore, though one will get cross waves heading in from where the big waves meet interference from natural promontories. I distinctly recall one crossing from my youth with our family of six and all of our gear piled into a 16 foot runabout with a 10HP kicker. We were headed across to the town of Atlin, a bit of a diagonal crossing from Atlin River to the town. With such a load, we had about 4 inches of free-board. We were mid-lake, two miles from either shore when the wind picked up hard and fast and the waves threatened to swamp us if we held our course.

We angled our course so that we were running in the trough between each wave, which made for a lot of side to side motion but reduced the risk of being swamped, as long as we had power and moved with the waves. We made landfall several miles above the town, having been carried that far off course by the need to work with the energy of the wind and waves. We spent the night huddled on the beach under sleeping bags, unable to light a fire even with gasoline to aid us.

The winds reached just over 100 MPH later that night.

This post has been edited by Under the Rose: 09 May 2012 - 08:09 AM

[arKane]

I'm surprised no one mentioned a tsunami. When a tsunami is generated it creates a wave that resembles rings spreading out similar to what happens when you toss a stone into a pond. So eventually those waves will contact land. I watched a program that showed what happened when a tsunami passed an island. Very nice wrap around effect causing problems on the backside of the island. I don't remember the stated reason for this, but think it happens because a tsunami is a very long powerful wave.

[Heedless]

When seen from a beach, the most noticeable waves are the ones close by and that have had time to build up in size. There might also be waves going away from the shore but they would be so young as to be invisible. Crest-to-trough measurements might be so microscopic that the water could look like plate-glass.