Tuesday, June 28, 2016

6/28/16 Report - How Water Sorts Things On The Beach. Gold and Emerald Finds.

Written by the TreasureGuide for the exclusive use of treasurebeachesreport.blogspot.com.

Gold and Emerald Ring and Gold Chain.
If you hunt where older people predominate you won't find nearly as much.  They don't do cartwheels or  dive for volleyballs, but they do lose some things.  The young people have been wearing more white gold, while the older people are still wearing a good bit of their older yellow gold.  The emerald ring is 14K, and the chain is 10K.  Both are recent finds.


A week or so ago I said I would explain why some days there are shells on the beach and other days not.  A lot of the same principles apply to coins.  I decided that I would have to repeat some things so you'd have some important background information.

As you would suspect, it takes more water velocity to move some items that it takes to move others. It isn't all about size or weight.  Density and shape are two important factors that I've discussed in the past.

While objects will be transported by water moving at a given velocity, it takes more velocity to dislodge settled particles and get them moving than it takes to keep them moving.

The velocity required to dislodge particles and get them moving is what I have referred to as the "trigger point."  That isn't the scientific term.  It is just the term I use.

Clay makes a good example.  It consists of very fine particles that transport very easily in water when suspended, but due to what I'll simply call the "stickiness," it takes a good bit more force to dislodge the clay particles to get them moving.

Different objects, in addition to having different trigger points, also have different "drop" points. When the water slows, there is a point when a particle will drop out or settle.  The same thing happens with objects.  When objects are being moved by a current, they will "drop" out, or settle, when the water slows enough.

The water has to be very calm before fine clay particles drop out, for example, while sand drops out while the water is moving a little more rapidly, and pebbles will stop moving when the water is moving still faster.

Below is one of the most helpful illustrations that I have seen.  It sums up a lot of what I just said.

In the illustration, the straight red line between the other two red lines shows the increasing velocity required to move larger particles and objects when a laminar current is assumed and other factors are not taken into account.

I won't try to explain what laminar flow is other than to say that it is a simple straight parallel flow. Look up "laminar flow" if you want.

The curved red line to the right of the straight line shows that pebbles are moved when the water velocity reaches near 100 cm/s.  The same line curves to the left as particle size decreases because it requires less water velocity to move smaller particles such as sand.  It then curves back to the right again because it requires faster water to get silt and clay moving.

The curved red line to the right of the straight line on the graph shows it takes more water velocity to move clay than pebbles even though pebbles are much larger than particles of clay.

The most important thing to get is that objects such as sand, coins, rings and all kinds of things, have different trigger points and require different amounts of water force to get them moving.  They also have different "drop" points, which is when they drop out of transport and settle on the surface.

Fine sand requires less current to get it moving and keep it moving than coarse sand or shells, but fine sand keeps moving as the water slows and shells drop out of transport.

Water flows up onto the beach, and then flows back down again.  When it washes straight up onto the beach, it washes back down the same path.  Sometimes an incoming flow hits the backwash, which stops the flow, and items drop out.

Lets say the water is moving up the slope of the beach fast enough to move the sand up the slope.  As the water gets higher on the slope, the water slows and the sand is deposited.  If the water is not moving fast enough to move the shells, then more sand gets deposited on the beach.  If on the other hand the water is moving fast enough to move both sand and shells, the sand might get moved farther up the slope than the shells, but if the water slows enough to drop the shells, but retreats fast enough to take the sand back down with, you will be left with a shell pile.

There are times, as we know, that the water washes onto the beach at an angle rather than straight up onto the beach.  When that happens, it does not slow so much at the peak.  The water also makes an arc, slicing onto and off of the beach, without being slowed so much.

The water moves onto the beach and back down with each wave, but there are also the tidal cycles to take into a account, and they are very important.  And there are still other things as well, such as where the waves are crashing.   It is not laminar flow (sorry if you did not look it up), but turbulent flow.

I ll stop there for today.  There are other important and interesting factors that come into play at different times, such as how compact the sand is.  I'll probably pick up with some of those topics some other time.

Much of what I said today I've said before, but I did add some.


There is still no tropical weather of any significance.  And we still have a small surf.

Happy hunting,