The physics of items sinking in the ground

[Rich jaws]

Have been doing a lot of detecting the past couple of months and have found a lot of clad and some silver and gold jewelry. Have found two large cent pieces and a number of wheats but no pre 1964 silver coins. Of course it depends on the type of soil, conditions, rainfall, temperature, etc. but does anyone else wonder what the sink rate of items would be in the soils they normally search. Just trying to understand the physics a little. It is a fascinating hobby metal detecting.

 

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[Rich jaws]

I don't think the tombstones moved I think the earth just got a little crooked. Lol

 

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[Rich jaws]

It really is hard to explain depth thumper. It is a very interesting subject and I never would have thought people would be so passionate about their position on the issue.

 

[RobRieman]

In just glad they do something to get under the ground. It would be a very different hobby if the didn't.

 

[Frankn]

Why do old tombstones lean? Is it because they have sunk a little? Or is that just the way they illustrate them in halloween cartoons!

View attachment 1094072

View attachment 1094073

That's amazing! I bet some of those head stones and monuments are over a hundred years old and thousands of pounds per sq. in. heavier than coins and yet they are still there. Does that tell you something? Yea some have a slight lean from improper tamping prior to instillation, but most are even still straight. Thanks for the example of what I said! Frank

These are much older. I don't remember if it was Ireland or Scotland.

 

[TheSleeper]

Gentlemen, perhaps all of you are correct, depending on the soil.

ON the desert, with min moisture, the ground is hard as a brick, its easy to understand an item laying on its surface for hundreds of years, unless it is covered by blown sand, debris from foliage etc. Think of a dust storm, people have been buried alive from one, towns have been destroyed and buried either partially or in whole by them. Read back in history about the dust bowl 1920's the wind storms that just about buried houses and people.

On normal soil, hum what is normal soil, the black fluffy humus soil so great for planting, the hard as a brick southern clay soil.

All this has a bearing on where an item will lay.


I believe that all of you are correct.

I believe that an object will sink if on a soft soil, esp after rain or snow has helped soften the soil allowing the object to find its point of balance (weight, density) versus the soil it is laying on.

I also believe that an object can be buried by falling leaves, decaying foliage, Wind blown soil, yes even if perhaps a dog stops and you know what on top of the object.

The tremors which we as humans cannot feel are always in effect, well soil, ground is effected by them.

As ground gets wet it expands, when it dries out it contracts, look at a desert the ground is cracked and split all over the place, why because it has contracted from the water (moisture) loss.

There are so many variables that come into play pertaining to an item's depth, that we as mere mortals will never be able to fully explain.

SO therefore gentleman, I think each of you are correct.

I am not going to try and discuss objects on sandy soil ie:beaches. Those only mother nature can explain.

 

[Rich jaws]

I would think they would be buried 10 inches up with decaying vegetation.

I agree with you sleeper. All of those factors need to be considered. Some feel that the only reason things end up buried in the ground is because of decaying vegetation which is silly. Of course that is a factor but is not the sole factor by any means.

 

[Frankn]

I see that some, although presenting no logical explanation of there own, Do not grasp the basics involved. Perhaps they should take a botany course.
Let me express it in basic steps.

-The coin falls to the surface of the ground.
-At the end of the growing season, or because of trimming, the leaves and grass cover the coin.
-The vegetation decays and in effect becomes soil.
-The new leaves and grass start a new cycle of growing drawing nourishment from the ground.

In effect the ground is constantly cycling, thus covering the coin.
There is no sinking involved.

This explanation should be simple enough for anybody to understand But there are always the lesser few.
Frank

 

[Treasure_Hunter]

I see that some, although presenting no logical explanation of there own, Do not grasp the basics involved. Perhaps they should take a botany course.
Let me express it in basic steps.

-The coin falls to the surface of the ground.
-At the end of the growing season, or because of trimming, the leaves and grass cover the coin.
-The vegetation decays and in effect becomes soil.
-The new leaves and grass start a new cycle of growing drawing nourishment from the ground.

In effect the ground is constantly cycling, thus covering the coin.
There is no sinking involved.

This explanation should be simple enough for anybody to understand But there are always the lesser few.
Frank View attachment 1094518
View attachment 1094519

Doesn't explain why some coins made after 2000 are buried 6 inches and others a lot older only couple inches deep in same area.

I hunt parks and find coins there near concrete picnic areas are buried 4-6 inches deep few feet away. If they were covered up by decaying grass and leaves why are they buried yet ground surface next to concrete hasn't changed levels, surface is flat as a pancake...


With that said why is it necessary to feel the need to try to insult or talk down to others and why does it even matter how they are covered up...

Please STOP insulting and talking down to members.





“A well-regulated militia, being necessary to the security of a free state, the right of the people to keep and bear arms shall not be infringed.”
― James Madison
The Constitution of the United States of America

 

[Treasure_Hunter]

Maybe this will be a soothing picture..

Sunset from Tampa yesterday....

 

[Rich jaws]

I think their answer to why some 2000 coins are deeper than others was that children bury them there or something to that effect. Roflmao. I am not insulted but thanks. There are still some that believe the earth is flat.

 

[Treasure_Hunter]

I think their answer to why some 2000 coins are deeper than others was that children bury them there or something to that effect. Roflmao. I am not insulted but thanks. There are still some that believe the earth is flat.

Glad your not insulted but the fact is it violates our rules and causes problems...

No kids burying quarters and dimes...

 

[TheSleeper]

Frankn, with all due respect: yes I agree with you pertaining to your theory, only so far as it being "one" of the many causes for items being buried.

Place a quarter on a slab of concrete, a hundred years from now unless covered by decomposing material that same quarter will still be lying on top of the concrete, naturally unless someone like me walking along doesn't pick it up.
Relate this to the ground, hard pack with min moisture content same principle applies ie: desert, barren hard packed ground, the great salt lakes etc.

Now the opposite end of the spectrum.

Quicksand, it is a form of ground, BUT due to its high water content heavier items sink over time, based on their density and volume. Meaning lets take a person for example, someone stepping into quicksand bears their entire weight on lets say 20 squire inches, the size of their boots. Hence their weight distributed upon 20 squire inches has more mass then the density of the quicksand thus they sink. Now that same person, but placed lying flat on their back, same weight but distributed over many hundreds of squire inches would float, proven fact, as long as they did not move or fight, panic.

Same principle with snowshoes, spreading the density of the item ie.person, over a hundred + squire inches versus 20 something.

Now both of these principles bring us to an interesting conclusion, unless you add in the constant moving or shaking of the earth.
Talk to any seismologist and they will tell you the earth is under a constant state of tremors, true most you never feel but they are present none the less. Ever been a quarter mile away from where construction is driving pillers into the ground for a building, its a distance away yet you feel it.

Here is an experiment for you if you would honor me by trying it.

Take a small jar of sand, place a quarter flat on top of the sand, now place the jar anywhere, where it will receive vibrations, not hard enough to disturb the sand or shake the jar, although the stronger the vibration the faster the reaction will be. Now just leave it, and over time you will discover that the quarter has sunk into the sand.

The time it takes will be directly proportional to the force of the vibrations, very soft vibrations will result in it taking longer for the quarter to settle deeper, versus violent vibrations which will result in the quarter sinking rather fast. A quarter stuck into the sand vertical will sink faster, since its volume(weight) is only being supported by the mass of its edge.

Now I used sand due to its softness, it is less dense than ground. Hence this experiment could be done over a matter of days (weeks) versus normal ground which could take a hundred or more years for the same outcome to be seen.

Here is another reason coins could be buried, floods. Massive water bringing washed out soil, trees, etc, when it pools the dirt suspended in the water separates and settles to the ground, if a coin just happened to be lying there it is basically buried.

In another scenario but covering a smaller area, a hard rain, we have all seen water puddles after a hard rain, is the water clear as the rain or does it look muddy?
Naturally it is muddy looking because the falling rain disturbed the top layer of ground which then mixed with the falling water. Now any item under that muddy water as the water dries will be covered with a thin layer of, drum roll please, dirt. Multiple this over a hundred years and how deep would the item be buried?

Frankn, there are just so many variables that we cannot begin to list, that could explain why a coin, from a hundred years ago is now 6" under ground to state that it is only due to one thing. We must keep an open mind and accept that perhaps others along with yourself could be right.

 

[sjvalleyhunter]

Frankn, with all due respect: yes I agree with you pertaining to your theory, only so far as it being "one" of the many causes for items being buried.

Place a quarter on a slab of concrete, a hundred years from now unless covered by decomposing material that same quarter will still be lying on top of the concrete, naturally unless someone like me walking along doesn't pick it up.
Relate this to the ground, hard pack with min moisture content same principle applies ie: desert, barren hard packed ground, the great salt lakes etc.

Now the opposite end of the spectrum.

Quicksand, it is a form of ground, BUT due to its high water content heavier items sink over time, based on their density and volume. Meaning lets take a person for example, someone stepping into quicksand bears their entire weight on lets say 20 squire inches, the size of their boots. Hence their weight distributed upon 20 squire inches has more mass then the density of the quicksand thus they sink. Now that same person, but placed lying flat on their back, same weight but distributed over many hundreds of squire inches would float, proven fact, as long as they did not move or fight, panic.

Same principle with snowshoes, spreading the density of the item ie.person, over a hundred + squire inches versus 20 something.

Now both of these principles bring us to an interesting conclusion, unless you add in the constant moving or shaking of the earth.
Talk to any seismologist and they will tell you the earth is under a constant state of tremors, true most you never feel but they are present none the less. Ever been a quarter mile away from where construction is driving pillers into the ground for a building, its a distance away yet you feel it.

Here is an experiment for you if you would honor me by trying it.

Take a small jar of sand, place a quarter flat on top of the sand, now place the jar anywhere, where it will receive vibrations, not hard enough to disturb the sand or shake the jar, although the stronger the vibration the faster the reaction will be. Now just leave it, and over time you will discover that the quarter has sunk into the sand.

The time it takes will be directly proportional to the force of the vibrations, very soft vibrations will result in it taking longer for the quarter to settle deeper, versus violent vibrations which will result in the quarter sinking rather fast. A quarter stuck into the sand vertical will sink faster, since its volume(weight) is only being supported by the mass of its edge.

Now I used sand due to its softness, it is less dense than ground. Hence this experiment could be done over a matter of days (weeks) versus normal ground which could take a hundred or more years for the same outcome to be seen.

Here is another reason coins could be buried, floods. Massive water bringing washed out soil, trees, etc, when it pools the dirt suspended in the water separates and settles to the ground, if a coin just happened to be lying there it is basically buried.

Frankn, there are just so many variables that we cannot begin to list, that could explain why a coin, from a hundred years ago is now 6" under ground to state that it is only due to one thing. We must keep an open mind and accept that perhaps others along with yourself could be right.

Very well said.

 

[Local_coins]

Do you ever notice the grass pattern in the dirt under the coin? I have seen that up to 7" - pretty cool.

Can you elaborate on this?

 

[Johnnoh]

Can you elaborate on this?

As the coin gets covered (or "sinks") the grass under the coin eventually decomposes but the pattern persists.

 

[Jason in Enid]

As the coin gets covered (or "sinks") the grass under the coin eventually decomposes but the pattern persists.

One step further... when the coins are sandwiched, the grass doesn't always decompose. I have seen blades of grass between coins in the ground for 100 years.

 

[FreeBirdTim]

-The coin falls to the surface of the ground.
-At the end of the growing season, or because of trimming, the leaves and grass cover the coin.
-The vegetation decays and in effect becomes soil.
-The new leaves and grass start a new cycle of growing drawing nourishment from the ground.

In effect the ground is constantly cycling, thus covering the coin.
There is no sinking involved.

This explanation should be simple enough for anybody to understand But there are always the lesser few.

There are small tree stumps in my yard from trees I cut down at least 20 years ago. I cut them about 3 inches from ground level, but guess what? They're still sticking up 3 inches from the ground and I still hit them every year with my lawnmower! I don't use a bagger on my mower and most years I don't even rake my leaves! Why aren't all those grass clippings and endless oak leaves covering up those pesky stumps by now?

Sorry, but your theory is just as flawed as all the other theories posted here.

 

[Rich jaws]

There are small tree stumps in my yard from trees I cut down at least 20 years ago. I cut them about 3 inches from ground level, but guess what? They're still sticking up 3 inches from the ground and I still hit them every year with my lawnmower! I don't use a bagger on my mower and most years I don't even rake my leaves! Why aren't all those grass clippings and endless oak leaves covering up those pesky stumps by now?

Sorry, but your theory is just as flawed as all the other theories posted here.

Good points. I have the same problem with those pesky tree stumps. I wish they would get covered already lol. In any event, I firmly believe it is a combination of all of the factors discussed above. Depending on the climate, vegetation, soil conditions, etc., certain factors are more at work than others. But clearly it isn't just decaying vegetation as you point out.

 

[watercolor]

One step further... when the coins are sandwiched, the grass doesn't always decompose. I have seen blades of grass between coins in the ground for 100 years.

This entire thread has been very interesting & enlightening. Lots of good info.

I found this Buff with a Wheat penny on top of it with a blade of grass sandwiched between them.
I was surprised to still see the grass pattern's relief on the nickel after I cleaned it.

 

[Nugs Bunny]

After reading through this thread I decided to do a little research of my own. There is a difference of opinion on how coins end up where they do and I'm not busting anyone's chops or trying to start a fight. My intent is to provide information on the physics and geology of soil to the OP and not take sides or disprove anyone.

I will post the links where I gathered the information at the end of this post.

Here is where my opinion ends and the science begins:

Soils build downward they do not accumulate upward. Soil itself is very complex. It would be very wrong to think of soils as just a collection of fine mineral particles. Soil also contains air, water, dead organic matter, and various types of living organisms. The formation of a soil is influenced by organisms, climate, topography, parent material, and time.

Additions

Organic matter that accumulates in soils includes the remains of organisms, plants and animals, but mostly plants. When plant debris falls onto the soil surface it may accumulate to form a surface litter layer or it may be mixed into the surface mineral horizons. Organic matter also may be added directly to the soil from roots and by animals.

Translocations

Most soils swell when wet and shrink as they dry. In some soils the magnitude of change with wetting and drying may be quite small, whereas in other soils it may be fairly large, for instance deep, wide cracks may extend about 1 m (3.3 ft) into some soils during dry seasons. Soil material from the surface often falls into the cracks. When the soil becomes wet and swells, the cracks close exerting pressures upward because of the added excess material that fell into the lower horizons (Figure 17). Soil material then is forced toward the surface. With time, these soils invert themselves. Material originally in the subsoil moves up and becomes the surface soil and the surface soil becomes the subsoil. Soils that exhibit this phenomenon are Vertisols.

Soil Evolution

One of the most interesting aspects of soil is its constant flux, ever-changing. Soil "begins" its "life" as parent material at the surface, due to some depositional event like the fall of ash from a volcano or silt or from the dust storms that accompanied the end of glaciation or due to exposure of older rock or material by erosion. In any case, it's basically just rock or loose sediment.

Once exposed at the surface, several processes begin to work. Organic matter accumulates, until a balance between deposition and decomposition is reached. Weathering of minerals leads to 1) release of soluble nutrients (K, Ca, Mg), which may be carried away by water and 2) formation of clays. Water percolates through, carrying clays and colloids downward and to accumulate at water table (where speed decreases) or where water is spread too thin to carry it onward (translocation). Later, roots and burrowing animals will play a significant role.

The Soil Profile

There are between 15,000 and 20,000 soils in the United States. These soils are differentiated from one another by the characteristics and properties of their profiles.

A soil profile is a physical and chemical description of the layers (called horizons) that make up the soil, from the surface to the depth where pedogenic (soil forming) processes are no longer evident. If a person digs a hole in the ground and looks at the wall of that hole, he is looking at the soil's profile. The horizons of the profile have formed and differentiated from the original parent material in place—they are not the result of geologic processes, although some features of a profile may be caused by geologic events (faults, lithologic discontinuities, buried soils, etc.).

Stages of Soil Formation

All soil formation begins with the accumulation of parent material. The next step is the buildup of organic materials at the surface. Pioneer species live and die, and organic matter begins to build up on the surface of the material and also beneath the surface in the rooting zone.

The A horizon starts to form once enough organic matter has been transformed by soil biota into humic materials. The humic materials coat the soil particles, coloring them brown and black. The formation of a recognizable A horizon takes decades or, in some cases, centuries.

The B horizon begins to form as dissolved and suspended materials are carried downward to greater depths with percolating rainwater. These materials include humic substances, suspended clays, salts, and metals, including iron and aluminum. It is likely that the largely insoluble iron and aluminum cations and oxides move in complex with dissolved organic material (chelation), and also in complex with suspended clay minerals.

The A horizon continues to increase in thickness, and the B horizon continues to develop. The A horizon will increase in thickness and SOM content, until it reaches a steady state in which the rate of fresh organic matter additions equals the losses by decay, illuviation, and erosion. This steady state is affected by certain environmental changes, including climatic change and vegetational succession (or cultivation). The B horizon will continue to receive illuviated material as it is formed in the A horizon, or sometimes as it is deposited on the surface (especially wind-blown clays).

Soil Composition

While a nearly infinite variety of substances may be found in soils, they are categorized into four basic components: minerals, organic matter, air and water. Most introductory soil textbooks describe the ideal soil (ideal for the growth of most plants) as being composed of 45% minerals, 25% water, 25% air, and 5% organic matter. In reality, these percentages of the four components vary tremendously. Soil air and water are found in the pore spaces between the solid soil particles. The ratio of air-filled pore space to water-filled pore space often changes seasonally, weekly, and even daily, depending on water additions through precipitation, throughflow, groundwater discharge, and flooding. The volume of the pore space itself can be altered, one way or the other, by several processes. Organic matter content is usually much lower than 5% in South Carolina (typically 1% or less). Some wetland soils, however, have considerably more organic matter in them (greater than 50% of the solid portion of the soil in some cases).

Sources

Encylcopedia of Earth - Soil

NOAA - Soil Composition and Formation

Illinois Wesleyan University - Soils

University of Arizona - Soils, What They Are and How They Form

Here is an interesting article at Minelab on the subject Minelab Des Dunne - Why do coins sink?