Why coins sink?

I can't explain the scientific reason why coins sink---it's rather deep? ;D (get it) Booooo!

Many things like you mentioned also contribute to their "downfall."
 

I can't answer that question. But I am amazed how an aluminum can will be 3 or 4 inches deep in soil that has not been disturbed. Parks are a good example.

AK in KY
 

In my experience the coins get covered with soil when it rains or wind blows soil over them. Waves at a beach wash sand over objects and coiln by their nature are haeavier than a like amount of soil. They will "sink" till they reach a root, rock or heavier material where they will stop. Frost moves the ground up and down depending on the temperture changes too. More targets are missed due to not overlapping the coil swings or not keeping it close to the ground thru the whole swing.

HH,

Sandman
 

It's kind of like quicksand, only thicker. When you add water to soil, and it becomes saturated, it is in effect a liquid. Metal sinks is a liquid. The thicker the liquid, the slower it sinks. A coin will sink much slower through clay than it will through freshly turned topsoil.

By the same token, if the soil doesn't retain the water, then it can't be a liquid. For example, if you had a pile of gravel and you placed a coin on top and the drowned the pile with the garden hose, the coin will still be on top. Do this same test with a pile of loose topsoil and the coin will sink a bit.

If this still doesn't make sense, think of it this way. Muddy water is mud too. Just more water than dirt. I coin will go straight to the bottom. As the dirt to water ratio increases, the coin will sink slower and slower.

Hope this helps!
:) :) :)
 

In areas where the temperature gets below 0 degrees for part of the year, you have something thats called Frost Heave.
That in it's self can cause objects to sink or surface up to a foot.
 

Don't forget about decomposition. Every fall when the grass dies and the leaves fall, they all turn into compost. So every fall you get a little more soil made on top of what ever was lost. Maybe a 1/16th to 1/8th of an inch or less per year. Over a 100 year or more time the duff builds up. :o
 

Something I haven't had the chance to research much yet is, MDing a currently farmed field that gets plowed and disked every year.
I've been told, when I made the comment about not bothering with a working field to someone, They said NO! those fields produce all the time, the working of the field brings stuff up and down all the time. Several Meteorite hunters have been said to hunt plowed fields on a regular basis. Just touching on the up and down thing lol. When you look at the ground you walk upon everyday, you get the feeling it's solid, but it really isn't.
Dano.
 

I do know that in Egypt ancient artifacts can be 3 or more feet deep. If you've ever been over there and experienced their dirt storms you'd know why.

But even here in North America ancient finds can be extremely deep. I know a fisherman who finds arrowheads while digging holes to bury fish guts (sorry bout that). He finds them 15 to 20 inches deep.

I believe many items continue to sink over time. Some sort of suspend at 3 to 5 inches but I don't know why. I saw a 18th century flintlock pistol bulldozed up from some 8 feet down while digging a house basement. Nothing else was found at the site.

This sinking thing is VERY interesting.
 

I don't believe that the coins "sink", I think that they get covered up by decaying vegetation.
Just my opinion.

Do sidewalks sink, or does the grass and soil on either side get built up?

I do believe that a coin can move around somewhat due to moisture in the ground freezing and thawing, worms, gophers, and other critters digging, and tree roots growing under a coin.
 

I do think coins as well as anthing valuable sinks.....as soon as I wave my detector over it and start digging...it sinks rapidly....dig four inches...says its still four inches deep...dig another four....still four more to go.....dig dig dig ......says :'(keep digging fool ...so i do ........................
 

bk said:
I don't believe that the coins "sink", I think that they get covered up by decaying vegetation.
Just my opinion.

Do sidewalks sink, or does the grass and soil on either side get built up?
Click to expand...

Yes, in fact sidewalks do sink. When the snow melts I'll get some photos of a sidewalk that's mostly sunk down below the surrounding terrain. I plan to detect this walk this summer.

Parts of the walk are 2 to 5 inches lower than ground level and it has sod growing over it. There's been no development in this area for over 80 years and there are no trees there. I discovered this a couple years ago but haven't taken the time to detect the area yet.
 

im leaning to BKs answer tho there are variables try detecting your local high schools playing feild youl see the newer coins 200? on top to an inch 90s 2nd inch 3rd inch 80s 4th 70 and so on there are variables to this but this is what ive noticed were there are no trees to add to the soil build up.i have dug a zinc at like 6- 7 inchs in a soccer feild thst was back filled so...VARIABLES there lots of them so no real solid RULE of thumb. my 2 wheats
 

It's all about water content of the soil and weight distribution. Wetter soil will not support a more dense object than the soil. A sidewalk will sink if the soil below it becomes saturated with water. Keep in mind that a concrete sidewalk also acts as a water shed, keeping the soil below it dry. Weight distribution also plays a big part in the equation. A sheet of plywood laying flat in the mud will support a lot of weight, but put that same sheet of plywood on it's edge and see if it'll support that same load.
 

every so often the county paves the road through my subdivision and for a year or three the blacktop is above the surrounding yards, but eventually the yards finally reach the level of the blacktop. Does this mean my road is sinking?
 

The earth is not a dead non-moving thing. There's action deep down which travels to the surface. For a more intelligent explanation there are books on this subject at the public library.

Some people think of this planet as this big hunk of dirt that only changes from external actions. This is not true. If you've ever seen a volcano on TV you shouldn't have any difficulty accepting this fact. The old dreaded earth quake is only too obvious.

Go to any ancient dig site and you'll find the main floors of houses 4 to 6 feet below the surrounding landscape.

Yes, most things do sink and some go faster than others. Sidewalks are usually very slow in descent due to their being supported on both ends. But if you drive through the old part of town you'll find places where the sidewalk dips down and there may even be dirt on top of it.

As for coins, many things aid them in their descent. Such things as vegetation, rain, wind, landfill, being stepped on, etc.

Coins usually sink very quickly to about 1 to 4 inches. Then they either are pushed back up by forces such as the frost/thaw action or they sink even deeper.

I've dug Memorial pennies not 20 years old at depths of up to 7 inches! At the same level or less I've dug coins dating to the early 19th century.

Single coins have been found very deep. Where they purposely buried deep as a cache or did they sink to that level? That can be a hard one to prove.
 

I agree that there are forces that can make objects move around in the ground, but if you say you see dirt on a sidewalk, how do you know that its because the sidewalk is sinking? Could it not be because the dirt got washed onto it? That seems to make more sense to me.
The other thing I don't understand is, why are coins deeper in areas of thick vegetation versus areas where the grass is very sparse? Do the coins sink deeper where there is a lot of grass? ???
Maybe it's because the grass allows loosening of the soil allowing the coin to migrate downward, and the hard packed dirt doesn't.
I don't have the answer. I think there are too many variables to make a definitive assumption.
 

bk said:
I agree that there are forces that can make objects move around in the ground, but if you say you see dirt on a sidewalk, how do you know that its because the sidewalk is sinking? Could it not be because the dirt got washed onto it? That seems to make more sense to me.
The other thing I don't understand is, why are coins deeper in areas of thick vegetation versus areas where the grass is very sparse? Do the coins sink deeper where there is a lot of grass? ???
Maybe it's because the grass allows loosening of the soil allowing the coin to migrate downward, and the hard packed dirt doesn't.
I don't have the answer. I think there are too many variables to make a definitive assumption.
Click to expand...

Usually sidewalks get 3 to 6 inches of dirt and sod because they sink well below the surrounding landscape. The rains wash the dirt in because the sidewalk is now lower than the surrounding landscape. Even back in the old days workers made sidewalks higher so the rain would help clear them of mud.
 

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