Tuesday, September 22, 2015

9/22/15 Report - How Coin Lines Are Formed: The Basic Beach Dynamics. CSS Georgia Salvage.

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

Yesterday I talked about finding coin lines.  Today I will attempt to illustrate the basics of how coin lines are formed.

The above illustration shows how the amount of water and force decreases as it goes up the slope of a beach.

The key concepts are those I've mentioned many times before.  First is the trigger point, which is the amount of force needed to pick up and move specific objects - in this case coins.

The force is greatest near the bottom of the slope and decreases as the water goes up the slope, sometimes eventually ceasing altogether.

At some point the water slows enough that it can no longer carry the objects and they settle out.  In my simple diagram that would be about at the number two.

That is the most simple scenario capable of creating a coin line.

However, not only does the water rush up the slope, very often there is a backwash.

In this illustration the red line shows the backwash.  If the water retreating back down the beach is strong enough to carry coins, it can carry coins back down the slope.

Remember, when the water slows to the critical "drop off" points, objects will be dropped.

But different objects have different "trigger points" as well as different "drop off" points.  Both the surge and the backwash can move coins and sand, or if not strong enough to move coins, it will just move the sand, leaving coins behind.

If the backwash has enough force it will carry coins back down the hill and also sand.  Sometimes it will have enough force to carry sand but not coins.  That applies to both the surge and backwash.

To additionally complicate matters, the coins can start out either in the water or in the sand.  They can be washed up or down.  They can be carried up the beach and dropped off at some point, or if they start out in the sand, they can be uncovered as the sand is washed away and washed down the slope.

A coin line can be very narrow when the surge is consistent or wide when you have a waves and a surge that varies more.

Once a coin gets covered by sand, it can be protected from the flow of water, which will flow over it without moving it until the sand is moved and it is uncovered.  If the water is moving enough to move the coin, of course it will also move the sand.

The backwash can be very strong in some cases, and in others virtually non-existent.  The balance between the two is important.  You'll often see the surge colliding with the backwash,

This is overly simplified, but I think it is still a decent illustration of the key concepts.

I'll possibly add to this in the future, considering things such angles, different sources and abrupt changes in beach profiles.


Terry T. recently found these coins in a coin line.  You might remember that I mentioned that discolored coins are good signs or markers.  They have been out there long enough to have been sifted and sorted and dropped in a line.

Coins Recently Found In A Coin Line On The Treasure Coast.
Photo submitted by Terry T.
Here is what Terry said in response to yesterday's post about a coin line.

...All in the picture were found to the south of a public beach about 300 yards a few days ago. I had about an hour to detect. A cut approximately 3 ft ran for about 60 yards. 26 years ago people were able to park off of A1A on top the dune very close to the beach ( an old party spot). I have got stuck there many times in the sand. Only to come to the conclusion that a couple of 8 inch wide pieces of wood cut 3-4 feet in length stored inside my vehicle, and a little patience along with a small shovel (and a lot of sweat back in the day) would get me out of the situation. Now AAA will be called -lol. All are modern U.S. coins, but have been there for sometime ( I excluded the pop tabs - both modern and old school types from the picture). Not one fishing sinker was found - nor any gold, but this area has produced gold in the past along with other items. I went back 2 days later after digging the coins in the picture, and the cut was filled in. She hides it well.....

Thanks Terry.

The primary purpose of hunting a coin line is not to find modern coins, but they can also be made of old coins and sometimes even better things as well.  The thing about the coins is that they reveal a pattern that can then be exploited.

Any old green coin like those shown above can be a sign of a coin line or coin hole.


Many artifacts and a 9,000 pound Dahlgren cannon has been recovered from the wreck site of the CSS Gerogia.

Here is that link.



It looks like Ida will fizzle out in the Atlantic.  There is a disturbance to the north of Florida that can be helping some of the states to the north of us.

The Treasure Coast is supposed to have a slowly increasing surf for the next week.  I'm not real hopeful.  We are getting into the Fall when typically we get some kind of storm.

Happy hunting,