4/16/19 Report - A Chest Full of Bogota Two-Escudos. Cuts, Cliffs, Flow and Erosion.

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

Bogota Two Escudo in Sedwick Auction (Lot 30)

Source: Current Sedwick Auction Listing.

Have you heard of the Mesuno Hoard?  The Mesuno Hoard consists of Bogota two escudos from the early years of the Bogota mint.  They are mostly dated 1628 to 1635.

The hoard was found by a poor fisherman who found a chest full of gold coins in 1936 in the Magdalena River near Honda, Columbia, when he went to check his fishing lines.  He shared the coins with his two brothers.

It seems that a boat carrying a shipment of coins to Cartagena was lost in the river.  From what I've seen of photos of the river today, it wouldn't have been a large boat.

I recommend that you read the very interesting and detailed Sedwick article about the hoard.

Here is the link.

https://www.sedwickcoins.com/articles/mesuno.htm

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Yesterday I described two ways that cuts are formed on a beach.  The first is when the water hits at an angle and slices away the sand.  The second is when the water hits the beach straight on.  It seems to me that the second method does not happen often on a real beach.  Beaches don't cut real often anyhow unless there is something that makes the beach especially vulnerable, such as jetties, rocks, or renourishment sand piled where there otherwise would not be much sand.

A wave tank is obviously not exactly like a natural beach.  The wave tank has walls that channels the water both incoming and returning and also keeps the sand from spreading to the right or left.  In the wave tank, the waves are also equally spaced and of the same approximate magnitude.  At least that was the case in the video I posted yesterday.  If you watch waves hit at one of the local beaches, you will see they vary a lot.  You'll often see waves coming from two different directions.  They are not equally spaced, and as the tide comes and goes so the water moves higher and lower on the beach, unlike what was demonstrated with the wave tank.

With the cuts created in the wave tank, I observed three stages.  First there was erosion that caused the slope to become more steep.  Then the upper edge of the slope collapsed.  And then the cut increased in size and moved back on the beach.

Long ago I showed how water slamming into the face of the cliff causes slabs of sand to separate and fall to the base of the cut to be washed away by the waves that follow.  For that to continue the water level must increase or at least remain high.  If the water starts backing off, the cliff will not continue to develop.    As long as the water continues to slam into the cliff, the cut will slowly move back on the beach.

I haven't yet explained how cuts create hot spots.  I'll have to do that some another time.

If the water remains high or increases because of storm surge or an incoming tide, the water will be hitting the cliff with a lot of force and bouncing the water back down the slope.  When you have that kind of force moving back down the slope, more sand and other things will be carried with it.  The only thing to stop it would be the incoming waves.

For sand to be moved by water flowing over it, it first has to become suspended.  It takes more force to suspend sand or other materials, but once it is suspended, it takes less force to move it than it took to dislodge it from its resting place.

The sand in front of a cut will be repeatedly washed and permeated with each incoming wave.  I( believe that repeatedly crashing waves can cause liquefaction.

Here is a video showing how shaking saturated sand will behave when it is shaken.

https://www.youtube.com/watch?v=b_aIm5oi5eA

This is something that I've not been able to observe, but I suspect that if the sand becomes liquefied, it will flow off the beach at a faster rate, and secondly it will fail to support the sand on the slope above it.

I observed that effect myself.  If you are near the swash area where the sand is near the edge, if you step on it, it will quickly give way.  The sand above that, which is not as saturated and firmer, will hold your weight, leaving only an impression of your foot.

When the sand gives way, the sand immediately behind it also loses some of its support.

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I know that some of you won't be very interested in beach dynamics, but I am, and if you understand it better, you'll be better able to determine when and where cuts will occurs and what will happened to the coins and other objects.  Then you'll have a better idea of where to spend your time.

I colored some grains and put them in the small surf and traced their movement.  Hopefully my video came out well and I'll be able to show you that in the near future.  I'm afraid there was too much glare on the water.

I'll also talk more about cuts and how objects will move relative to them.

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I'm sure you all saw images of the fire at Notre Dame Cathedral.  Anyone interested in history had to be saddened by the loss of such a historic building.  Began nearly six hundred years before the 1715 Fleet sailed, it survived hundreds of years of history including the French Revolution, Napoleon Bonaparte, and World Wars, and was the residence of sacred relics such the Crown of Thorns, a stone from the Holy Sepulchre, and wood and a nail from the cross and many works of art, some of which were saved.


The tides are getting bigger, but there won't be much surf for several days.

Easter, if I correctly recall, falls on the first Sunday, after the first full moon, after the Spring equinox.

Happy hunting,
TreasureGuide@comcast.net

4/15/19 Report - New Explanation on Beaches and Cuts. Rare Strike-Over Half-Reale Coin.

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

Cuban Half Reale Struck Over U.S. Half Dime.

Source: Sedwick Coins auction.  See link below.

Here is an interesting coin that is listed in the current Sedwick auction - a Cuba 1/2 reale that was struck over a U.S. half dime.  There are other coins in the auction that were struck over coins of other countries.

Here is the lot description for this coin.

Cuba (Mayari), silver 1/2-real(?) token with incuse MORALES above 1 over 2 denomination, made from a US Seated Liberty half dime (1800s), very rare. 1.10 grams. One of very few examples known, all believed to be made from half dimes, this one to our knowledge the only one without a hole, with oversized arms (lions/castles) covering the entire reverse and the obverse punched with MORALES H(o) in a box above an incuse 1 over 2 believed to stand for 1/2 real. Clearly from the same series are some 10 centavos (supposedly) made on US dimes with incuse 10 and also a unique 20 centavos made on a Spanish colonial 2 reales (both of those denominations with JUNIO below the number), the last-mentioned with more of the reverse design showing a clear DE MAYARI below the arms. Toned Fine with no host-coin details showing.

https://auction.sedwickcoins.com/Cuba-Mayari-silver-1-2-real-token-with-incuse-MORALES-above-1-over-2-denomination-made-from-a_i33012333

This coin is lot 1020.

There are more strike-overs in the auction.  This one already has a bid of over $2000.

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These days I often hear people say "You don't know what you don't know."  There is some truth to that, but it isn't entirely true.  I personally have an unending list of things that I know I don't know and would very much like to know.

Sometimes it is very important to know what you don't know.  I wouldn't let a podiatrist do brain surgery on me, for example.  Experts should be especially aware of their limits, and have a deep respect for the boundaries of their expertise.

I previously described how cuts are created.  The one thing that absolutely has to happen is the water has to move with enough force to carry sand down the slope and out into the water.   I've described how that happens when the water hits the beach at an angle and slices sand away.

Below I have a video that I previously posted that shows how cuts are created when the water is hitting the beach at an angle - in this case, it is an extreme angle.  After that I have an excellent and very revealing video of an experiment conducted in a wave tank that shows how a cut can be created when the water is hitting the beach directly at a ninety degree angle.

Here is a video I caught that shows how a cut occurs when water hits the beach from an angle.  In this case the water flows almost parallel to the beach.  I showed this one once before.

https://www.youtube.com/watch?v=I8aCk1zC0e4

The cut is moved farther back each time the water flows along the face of the cut.  If the tide goes out and the water level drops but the water keeps hitting at a similar angle, another cut will be made lower on the beach.  You three different cuts at different levels in the video.  For a deep cut to be made the water has to keep moving along the cut for a period of time without the water level getting either much higher or lower.

That is one way a cut is created, however cuts can occur even when there is little or no angle to the water hitting the beach.

Here is a video that illustrates very clearly how a beach can erode when the water is hitting a beach straight on.  Watch closely.  This is great.

https://www.youtube.com/watch?v=y0C5sQ_NWs8

A wave tank is a different than a real beach in several ways, but the wave tank does help make some things clear.

If you carefully watch the beginning of the video, you can see a dip gradually form just below the highest reach of the water.  Watch from second three through nine and you will see a dip beginning to form.  The side of the dip highest on the beach continues to get steeper until finally it starts to collapse, and a small cliff (or cut) is formed.  The cliff becomes higher and moves farther back on the beach as the water continues to erode into it.  That is an excellent illustration that you couldn't see on a real beach in real time.

But that isn't all.  After the first cut, a second cut forms a little lower on the beach.  Why is there a space between the cuts, and why does the second cut form where it does?

What happens is that the sand from the first cut moves down the slope and that hump forms a steeper slope which focuses the force of the water and creates a new a new cut.

To sum it up, under specific circumstances such as those illustrated in this wave tank video, water hitting straight onto the beach CAN, under certain circumstances, cause a cut by first creating a dip that gradually increases until the slope is so steep that it begins to collapse, therefore creating a cut.

Steeper beaches return water at a speed and force that can carry sand down the slope (erosion).  Waves with less force cause lower wider beaches that deposit sand on the beach instead of pulling it back into the water.

A real beach is different in a variety of ways.  For one thing you don't have straight walls and the waves are more irregular in both shape and timing.  The beach is not straight either.  And the sand can vary in a number of ways, including grain size and compactness.

There is much more that you can see in that video if you keep watching, but that is enough to assimilate at one time.  I'll probably comment on more of what you can see in that video at some other time.  I do wish I could slow the video down.

Here is one tip if you want to study the video some more - watch the turbulent areas.

While on the subject I'll throw in one more video.

https://www.youtube.com/watch?v=05EQLQqKMGU&pbjreload=10

I didn't even get into what is special about cuts or why they are good for metal detecting.  I'll do that in the future.

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The tides are getting a little bigger.  Today there will be a small negative tide.

The surf is only around two feet.

As I recall, Easter is on the first Sunday after the first full moon after the Spring equinox.

I think what I posted today will help you understand beaches better.  There is more to come.


Happy hunting,
TreasureGuide@comcast.net