I do not believe the density equilibrium theory of coin sinkage

Let me first say, I am confident that coins sink; so, please do not clutter up this thread with pronouncements that coins merely get covered with decaying leaves and grass over the years. Even if you do not believe that coins sink, please accept this premise for the sake of argument here.

Now, on to my disagreement with the density equilbrium theory of coin sinkage. I have seen this so called theory, actually a hypothesis, quoted or posted in several places. The theory is essentially that coins will sink until the density of the coin equals the density of the soil.

This theory cannot be correct. Gold is one of the densest materials on earth. Even the most compacted soil is not going to have a density anywhere near to that of gold. I doubt it could even be done with the tonnage of a huge hydraulic press or explosives. On this basis alone, the density equilibrium theory should be rejected out of hand.

I'll offer an alternative hypothesis. A coin will sink until the stress exerted by the coin, due to gravitational force, equals the compressive strength of the soil. This of course assumes that the initial stress is greater than the compressive strength of the soil, otherwise there will be no sinking in the first place.

Stress is force per unit area; thus, a coin on edge will more readily sink than a coin laying flat, assuming all other factors are equal.



Edited 1 time(s). Last edit at 10/13/2016 05:09PM by Bayard.

I agree, the 'density theorem' is touted by people who don't even know what density is, I'm sure. It's utter garbage. Soil density hardly varies with depth, anyway, so not many items would end up 'balanced' density-wise.
I notice that aluminium ringpulls sink quite rapidly, despite having densities not too far off that of some soils, so it's not a significant factor in sink rate.
Bioturbation is the main reason for sink, in most soils. Pesky annelids burrowing their way about.

I think the sink rate is more related to Worms and ground movement, Tree and Grass roots or subject to rain fall, Not that I am correct but I am sure all these things contribute to soil and Items moving in the ground,

John.

combination of soil disturbance, sinking, and material build up.

Another theory silver half and silver dime dropped at same time will be the same depth due to density or size-weight of either...
Been there done that and a truism...

Good one Dan....... also consider they get covered up...... and even more so depending on soil.

Dew

My take is, soil type, amount of rainfall, freezing and thaw effect, insect, animal and human influence and material build up.



Edited 1 time(s). Last edit at 10/13/2016 11:29PM by Dan(NM).

There's a noticeable hard pan around here in alot of places that artifacts just flat stop at. We've brought equipment in on sites and it's amazing how many civil war artifacts were at 18-20". Smaller items that are out of reach of a detector.

Perhaps over many,many years they'd continue to sink into the clay but at a noticeably slower rate. Can't help but wonder if they get down that far before hitting that layer here, and after 150 years at that... how far will they sink in areas without it? There's likely a world of ancient coins 4 and 5 feet down.



Edited 1 time(s). Last edit at 10/14/2016 12:11AM by deadlift.

It may sound weird, but I think the answer is a big AND opposed to "do they sink or not". I'm convinced both possibilties and everything in between can occur according to conditions.

I have found a pocket spill of 120 year old coins in a forest under the proverbial rotting leaves in the humus.
I remember that so well, because the silver coin was shiny like new and the lesser coins around it were
eaten away like the cookie monster had taken a bite out of them.

I have also found things, how should i say, too deep for normality, like how the hell did that get down here?

I agree with all the factors mentioned above that can influence coin-sinking.

As to the density equilbrium theory for coin-sinking, I'd say bollocks. At least in most real-life situations.

Throw a coin in water, density about 1 and bingo, you're right!
Throw a coin on ice, density about 1 and oh, you're screwed.
Coins would would be able to migrate through concrete if that hypothesis were correct.

I suppose "compactness", "vibration" & "fluidity" would be some main contributors to try and figure this out.

In an area with many earth tremors or land close to waves crashing to shore I can imagine coins wiggling their way downward faster than usual in the terrain,
given the right "compactness" and "fluidity" of the ground.

In a nutshell their indeed are coin too deep for any detector..

If a coin sank/settled 1/16" in 365 days.....in 200 years it would be down at 12-1/2".....not including dust, organic debris covering on top. 1/16" (1.58 millimeters) isn't much.

My point is, it's a very slow decent. If the equilibrium theory is true, the closer it got to it's density, the slower it would sink....at that point it may take 10,000 years to sink 1/16". Just thinking out loud.

In woodland coins seem to go deeper, I have hit old UK pennies at 12 and 13 inches, Yet in open ground they have only been 7 to 9 inches. and then I have found small Silver coins in the top 5 to 7 inches, The trouble with this topic is there is no standard depth of Fall Rate in which to judge it by,

and yet I have found larger Silver coins at the 10 and 11" range that were lost around / During WW II, That place was the Hottest Finds Rate I have ever come across, The 2 days I was there netted me hundreds of Coins, even modern coins were in the 4 to 8 inch range, Yet it has never been ploughed and it has been a park for over a 100 years.

John.

Place a coin flat on the surface of inert soil in a large container, cover the the contaner and sit it in a non earthquake area. Check in a thousand yrs. IMO the coin will still be within a1/4 inch of the surface.
I have found numerous meterorites that have been lying on the surface for 40 thousand years, they sure didn't sink. Also gold nuggets with desert varnish on the surface, it take a long time for desert varnish to form.



Edited 1 time(s). Last edit at 10/14/2016 08:22PM by Hobo.

deadlift Wrote:
-------------------------------------------------------
> There's a noticeable hard pan around here in alot
> of places that artifacts just flat stop at. We've
> brought equipment in on sites and it's amazing how
> many civil war artifacts were at 18-20". Smaller
> items that are out of reach of a detector.
>
> Perhaps over many,many years they'd continue to
> sink into the clay but at a noticeably slower
> rate. Can't help but wonder if they get down that
> far before hitting that layer here, and after 150
> years at that... how far will they sink in areas
> without it? There's likely a world of ancient
> coins 4 and 5 feet down.

Well according to some if you want to go deep on coins you need an MXT with the 15" coil,

Quote 'you can expect to hit some coins well over 2 feet and beer cans deeper,

Although it is very big it is Hyper sensitive and very deep and if you are looking for Big Targets It might be a good idea to have a Backhoe close at hand'

deadlift Wrote:
-------------------------------------------------------
> There's a noticeable hard pan around here in alot
> of places that artifacts just flat stop at. We've
> brought equipment in on sites and it's amazing how
> many civil war artifacts were at 18-20". Smaller
> items that are out of reach of a detector.
>
> Perhaps over many,many years they'd continue to
> sink into the clay but at a noticeably slower
> rate. Can't help but wonder if they get down that
> far before hitting that layer here, and after 150
> years at that... how far will they sink in areas
> without it? There's likely a world of ancient
> coins 4 and 5 feet down.

That 15" Coil I have is very powerful, but it throws the balance of the machine right out the window, it can see Tiny things and it has the depth but the Weight is all wrong, Once you have used it you won't want to use it that often because it is hard work.

2ft+ coins, I'd use it every day lol

ghound Wrote:
-------------------------------------------------------
> 2ft+ coins, I'd use it every day lol

Yeah and 2 Hernia's and a slip Disc, If only it was light weight,

Density is just one variable. What about the hardness of the material below the coin? for example, plaster of paris is not particularly dense, but it is very hard. A coin would not travel through it. Clay soil is not particularly hard, but it is fairly dense.

Tom's dirt strata study. Conclusive analysis was achieved in May, 2000. The 1962 strata of dirt was located at 9.22" deep.

report located at this link.

[www.dankowskidetectors.com]

In my area the sink rate varies and further up north things dating back to the 1460s are found within 6 to 8 inches with 4 to 5 inches of dirt and any deeper turning to Clay, yet in the same patch of ground the Dirt can be a lot deeper.

I don't think any one theory can be applied to coin sinkage rates here in my area,,,,just too many variables.

Now maybe sand in Fla maybe,,but ot here.

I see too many older coins shallow and too many not so old coins deep.

Between tree roots,,rocks,,,solid mineral,and rodents,,,,,I just hunt,,,and don't assume anything depth wise about any particular site.

Been wrong way too many times ,,,,learned my lesson already.



Edited 1 time(s). Last edit at 10/15/2016 11:56PM by tnsharpshooter.

I can definitively say, based on my vast (well, half vast) experience, you are all, to a greater or lesser degree correct. However, as there are an infinite number of random variables it is way too complex to explain the physics in a way that covers every occasion/event. When you find a century old coin looking freshly minted under a dust layer then a 10 inch deep penny with nice patina that turns out to be a 2010, utter a socially acceptable epithet, shake your head and thank the coin fairies because they are really the only explanation that makes full, complete and perfect sense. You're welcome.

Past(or)Tom
Using a Legend, a Deus 2, an Equinox 800, a Tarsacci MDT 8000, & a few others...
with my beloved, fading Corgi, Sadie