Written by the TreasureGuide for the exclusive use of the Treasure Beaches Report.
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| Wave photo from Landscapes - Clark Little Photography |
I haven't talked a lot about how the beaches and objects on the beach move lately, but that will be today's topic.
You might have seen my famous, or perhaps infamous, photo of a coin and ring in a cup of sand and water. Here it is one more time, just for reference.
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| Gold Ring and Penny on a Layer of Sand Under Water. |
Detectorists often referred to coins and things sinking in the sand, which seemed misleading to me. I wouldn't call it sinking. In order for a coin to "sink" in sand, there has to be another force that moves the sand, which is where the emphasis should be. As my cup demonstration shows, the coin and ring will sit on the surface of the sand forever unless there is another force that disturbs the sand. And that force on the beach is the force of moving water.
At the top of this post you there is a beautiful and unusual photo of a huge wave. I'll get back to that in a little while.
Below is the same cup of sand and water after the cup was swirled.
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| Same Cup of Water and Sand and Objects After Being Swirled a Little. |
When I moved the cup, the water moved, which moved the sand. When the water cup and water was moved faster, even more sand was picked up and moved with the water. The surface sand moved first and most. The deeper sand moved less, and the deepest layers didn't move at all.
So what happened to the coin and ring when the cup and water moved? As the sand became suspended and moved, the objects settled lower to the more settled sand. That isn't surprising, but it was nice to see so clearly in operation.
The ring, offering less surface area than the coin, sand end up where the dark blue line is shown on the cup. The coin ended up buried at the lighter blue line.
I think the word "buried" describes the process better than "sunk" because the sand lifted, and the objects settled to the lower area and then were covered as the sand settled once again. I expected the ring to settle deeper and that is what I've observed at the beach. Coins offer a lot of flat surface area and settle on less densely packed sand. I know I'm using a very demanding definition of the verd "sink", and you might object to it, but I think the distinction is a good one because it moves the focus from the more passive object (the coin) and puts the emphasis on the forces that drive the process.
The little cup demonstration is simple one, but it provides an illustration of some very important basic principles. See The Treasure Beaches Report Direct From Florida's Treasure Coast.: 9/4/14 Report - How Coins and Rings Sink In Beach Sand. Targets Only Sink As Far As The Disturbed Layer.
In another experiment, I showed that the shape of an object affects the objects movement as well as the density of the object. As I've often said, but will repeat again because of the number of new readers, a ton of Styrofoam will float as will a steel ocean liner. It isn't just about weight. Both density and shape are important factors that will help determine where an object will end up on the beach.
The photo at the top of this post shows a large wave. Clark Little dives into crashing waves and gets the most interesting and informative photos. Here is a link where you can see more of his photos.
If you look at the photo at the top of the post, you'll see that the wave is picking up a lot of sand. The photo shows some very turbulent water and a lot of sand being being picked up. Not only can a strong wave pick up a lot of sand, but when the wave crashes, it will push a lot of that suspended sand up the beach. The crashing wave will also pound the sand as the water crashes down on the beach front.
Below is another Clark Little photo that gives another picture of sand being churned up.
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In the past, I haven't talked about this high impact zone as much as the mid and upper beach and the erosion that occurs there. Besides sand being moved, the larger force can move shells, rocks and other things. I've seen coins flip up at the top of the beach when a wave hits a cliff with good force, so it undoubtedly happens in this high impact area as well.
If you look at a lot of Clark Little's wave photos and carefully observe his videos, you can see how things work in the crash zone and beyond. Take a look at his videos where you can stop that action and replay it. Here is a link. SHOREBREAK: The Clark Little Story - Official Trailer - 1 Minute
One additional thing to remember is that as you go through the tide cycle, the waves will crash farther up the beach and then back down with the tide cycle. The crash zone will cover a fair area of the lower beach as the tide cycle progresses. As I've explained before, all of that might still not cause a cut beach. If the various forces are just cancelling each other out, you'll end up with mushy slope but not necessarily a cut.
Remember also that the sand washes up the beach and then back down. The inflow and outflow can pretty much cancel out. I won't go over again the conditions for a cut to form.
It is impossible to include all the factors and considerations in a single blog post, and I know I'm leaving a lot out, but I'm today I'm adding a little new material to what I've presented in various posts in the past. I hope it helps. It will make more sense if you put it all together with other posts related to the topic. The following chart is important and very informative. I've discussed it several times. Keep it in mind.
Here is a link to a previous discussion on that. Treasure Beaches Report: Pt. 2. (2020 and Beyond). : 4/8/25 Report - How Coins and Things Sink in the Sand Revisited: Informal Experiment and Discussion. Trigger Points and More.
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It looks like the Treasure Coast will get a couple days of two or three foot surf around Wednesday, then decreasing again.
Good hunting,
Treasureguide@comcast.net