Written by the TreasureGuide for the exclusive use of treasurebeachesreport.blogspot.com.
|Real Wave Photo.|
Now this is really cool. Believe it or not this is an actual photo. Beside being a beautiful picture, it shows something very interesting.
I'm not positive but I think the photo is a Clarke Little photo. He is a surfer turned photographer.
I lost track of the source, but here are more of Clarke Little's beautiful wave photos.
Take a good look at that photo again. Do you see what is happening? Look at the brown sand or whatever being sucked up into the wave. That is what I think is very interesting. It wouldn't be that apparent if you were just watching it happen, but when it is frozen in time like that you can really see it.
In my 7/16 post I showed this illustration. Notice how the waves move in circles. I've told before about how if you are floating in the deeper water, you'll move in a circle as a wave goes by.
As the wave gets in more shallow water the circles get flattened and turn into ovals.
What you are seeing in the top photo is the bottom of the circle where the sand is getting sucked back into the wave. The circle isn't completed here because the water is too shallow and the wave is breaking.
Just think about what is happening there. First the top sand is getting sucked out and then the wave comes crashing down with force just in front of that.
When the sand gets sucked up into the wave, as you can see in the photo, it is lifted, and then when the crashing wave impacts the sand with considerable force.
That happens time and time again as the waves come in, and each time in just a little different place.
A report by the Naval Warfare Center (http://www.dtic.mil/dtic/tr/fulltext/u2/a495574.pdf) says, Overall, average impact pressures from the breaking waves are greater in magnitude than the impact pressures from the non-breaking waves and average impact pressures tend to increase with increased speed...
OK. We knew that crashing waves have considerable force. I recently posted about blocks weighing tons being moved.
Big waves, as is obvious, stirs up a lot of sand, but in addition to the effect of crashing, there is also the sucking that we see in the photo. Add that to a near continuous flow running along with the long shore current on a steep beach and a lot of sand and stuff could be moved quickly.
Adding in any undertow or backwash, the net effect will depend upon a variety of factors, including the "trigger" and "drop" points for specific objects, as I've said before.
I think my understanding of how coins and objects get covered and uncovered is fairly complete. I've tracked and observed how objects move in many situations, but I have never been able track the movement of objects within big waves and during storms. I think I'm getting pretty close to a complete understanding of that part of the process too, which will explain how coins and things wash up at times.
Looking at the picture at the top of the post and how the sand is getting sucked into the base of the wave, I wondered if coins or other objects could get sucked up into the wave and actually thrown ahead with the water in a breaking wave. I don't know about that, but considering how easily coins flip (turn over) in relatively little current, I wouldn't be surprised if large breaking waves could throw some objects. Certainly they are blasted, lifted and moved, but maybe not through the entire cycle of the breaking wave.
In the photo, you can see some of the sand moving ahead with the wave.
It would only happen when the waves and obects are in shallow water. That is one condition. When the water is deep relative to the size of the waves, the bottom and objects on the bottom are not affected.
When we have storms, some waves are breaking on a slope rather than a flat bottom like we see in the photo. I
I didn't really want to introduce the complication of the different types of waves yet, but I unintentionally just stepped into it.
Besides breaking waves, there are other types, such as plunging waves and surging waves.
According to wikipedia
A plunging wave occurs when the ocean floor is steep or has sudden depth changes, such as from a reef or sandbar. The crest of the wave becomes much steeper than a spilling wave, becomes vertical, then curls over and drops onto the trough of the wave, releasing most of its energy at once in a relatively violent impact. A plunging wave breaks with more energy than a significantly larger spilling wave. The wave can trap and compress the air under the lip, which creates the "crashing" sound associated with waves. With large waves, this crash can be felt by beachgoers on land. Offshore wind conditions can make plungers more likely.
That is as much as I want to get into that for now.
I've known for a quite a few years that coins wash up onto the beach. There is no doubt about that, but perhaps large crashing waves can move sand and objects in even more dramatic ways than I previously suspected.
For a relatively thorough explanation of waves, you might want to look at the following.
132 year-old Winchester rifle was found propped up against a tree in the desert. Nobody knows what happened to the owner or how it got there.
It seem that the Treasure Coast is in for a couple more weeks of one-foot surf. How long can this last?