DO THEY SINK OR DO THEY FLOAT ?

[diggemall]

Since I have started "lurking" on T-Net, I have seen a few references to the idea that older coins are hard to find because they sink over time. However, I have also read just as many references to finding old coins within a few inches of the surface. I can't quite wrap my head around this whole thing.

I'm in black soil farm country up here in Wisconsin. Every other year or so most of the farmers pull a wagon back and forth over their fields while their kids pick stones. Now, these fields have been worked since the 1880's, and the mold-board type plows used around here only turn over the top 8 or so inches of soil. If dense objects "sink" in soil, why is it that they seem to have a perpetual supply of new stones to pick up ?

In these same conditions, in the spring, when the soil is so saturated you can sink well past your ankles, stones on the surface just stay there.

It seems, at least in the northern climates that, if anything, the yearly frost helps to work objects UP towards the surface, providing that steady supply of stones. (Around here frost routinely reaches 3 feet and can go as deep as 6 feet)

In turf conditions, I can see objects "sinking" as topsoil builds above them rather quickly with continual mowing and the like, and decomposing thatch (maybe at the rate of a quarter inch every ten or so years)

Likewise, in extremely wet mud, I can see objects sinking over time, but there aren't really that many areas that are that wet for more than a couple days each year that would also bear any kind of public use (i.e. not too many people picnic, or build a house right in a swamp)

I have found a couple objects that seem to support the sinking theory (like a pipe wrench down 18 inches or so) but they could also be explained by fill having been brought in.

I'd like to hear everybodys opinions on this one, and whatever evidence they have to back those opinions up......

Diggem'

 

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[Will_detect4food]

here in Florida things seem to sink, I have found coins that are not that old 6 inches down. And at the beach items sink very fast, A lady asked me to help here find an earring she had just lost in the dry sand. it was about 4-6 inches already when i scooped it up, just from the traffic they made looking for it

 

[Jeffro]

And lets not forget about earthworms continually loosening the soil underneath dropped coins....

I have no clue as to why some coins sink and others appear not to. I found an 1854 seated dime at 3 inches, and just today I dug a 1960 cent at 6 inches.

Amounts of clay in the soil, amounts of rocks, sand, etc. could all play a part, as well as if the general area is somewhat protected from the rain, like under a tree.

The dime was found under a tree, where the roots may help hold the soil tighter together, whereas the cent was found in my lawn, where grass clippings keep piling up over the years and the earthworms are lovin the loose soil.

The clay layer in my yard is about 2 feet down, which helps hold moisture on the surface, but the area where the dime was found, it is almost at the surface.

I think that the soil conditions can change so drastically from mile to mile that "you never know what you're going to get", kinda like that box of chocolates....

No answers, just my theories.... anyone else got any?

 

[Sandman]

This is a deep question and all I can add is the soil is different in different parts of the country. Like the stones that seem to stay on top, some sink till they touch something that holds them from going deeper. Frost moves things and so do plant roots. I have found old coins barely covered with soil and newer coins a foot deep in the woods. At a sea shore things are governed by different laws of erosion, currents, tides, storms, etc.

Don't dwell on depth, just go for it.

Sandman

 

[Rusted_Iron]

Frost sure does move things around. Look what an "ice lens" can do to a road. Picks it right up.

As you said, the rocks keep coming up to the surface even in areas that are plowed a lot. I definitely have found things with my MD in places where I don't remember getting a signal just one or two years before.

 

[bakergeol]

The best studies of this were conducted by the military regarding UXO. Just google frost heave and UXO and there is abundant information. In some areas frost heave can lift UXO up an inch a year. So yes rocks can be lifted up by frost heave. If memory serves me right there was a weight limitation so heavy munitions could not be lifted up(if that wasn't true we would just wait for all of those iron treasure chests to be lifted up). In addition the shape of the object was important too- so coins were not heaved up.

George

 

[ringding]

Down here in Georgia there is clay in the ground and it is like concrete when it is dry. Coins don't sink in this soil. You can find many coins laying on the surface or within 1" of top. In the woods coins can sink in soild because there is organic matter on top of the clay. Leaves drop and decompose and build up the soil on top of the coins.

 

[LadyDigger]

I metal detected my yard and was amazed that I found 2 quarters (these new design ones), one on top of the other ... about 5" or so down...yet, I found 7 wheat pennies in my yard (recent finds ) just a few inches below, except for one...it gave me a ride for my money...it was deep...but I got it!!!! By the way, these are quarters my boys probably threw in the yard....kids, gotta love 'em!!! (and I have started my boys on coin collecting...they are loving it!!)

Also, I read somewhere, that after a good rain is a good time to go out detecting. I did this after some good rain here this past week and in areas I already detected is where I found the wheat pennies (I found all 7 this past week, not in the same hole, but within a few feet of each other.) So, does the wet ground give you better readings in the soil? I would say it did!!!

But in our yard, which was farm land prior to this house being built in the mid 60's....very hard clay (on dry days, somewhat soft after a good rain)....about....I would say 6" and below. We have alot of clay in this area!!!! I don't like clay except to mold!! . We are also on a creek bank.

We detect at the beach as well. They, of course, rack the beach every morning here, which prob either pushes items further in the ground or pulls it up...and please don't take this wrong, but I can't wait for a good storm to come through. If there was a way to get a hurricane, but without the damage...that would be awesome. I can't wait to detect the oceanfront after a good storm!!!!!!!! (Which I heard this morning, we have our first tropical depression already)

So, I guess (as someone mentioned here) it would depend on where you live, the soil and such....really hard to say. And eventually, even though I have lots of clay....eventually items will sink into it...as I found an old spoon at the side of my house, buried very deep and clay encrusted!!!!

 

[jeff of pa]

Depth & time it takes to Sink Definately depends on Conditions.

If a coin is dropped when or where it is muddy it is definately going to sink quicker then a coin dropped on dry ground. at least till it rains.

get your kids to make a mud pie. lay a quarter neatly on top after.
fill another pot with dry soil, lay the quarter on top. & water it every time it rains.

Gravel ground is going to hold coins up longer then regular ground.

walking on & dust blowing also make a difference.

I think coins in grass sink quicker in grass that is mowed more regularly. although sink may be the wrong word here.

TOO Many Variables

Congrats n the finds by the way.
Jeff

 

[Don in SJ]

In general I think coins in parks/lawns and in undisturbed woodlands do not sink. If you read some of the Archie information on the web, you would not use the term sink for a lot of the reasons given in previous posts to this thread.

I believe the correct term and what is actually happening is the "deposition of soil". Think about the archeological digs you see on TV, the dig down through layers of soil, each representing a time in history. Good ole Mother Earth has a lot of dust in the air that is always being deposited and grass clippings, leaves decaying all add to the height of the land.

I worked at a former WW2 Naval base and the old sidewalks were still there but the buildings for the most part were torn down in the 70's. The sidewalks were all about 2-3 inches LOWER then the surround grassy areas. Yes, I detected there and was finding Mercs and Wheaties at 3-5 inches in general. So, did those coins "sink" since WW2? No, just settled a bit in the dirt but the vast majority of the 3-5 inches was from 50 years of grass clippings and dust in the air settleing onTOP of the coins.

So imagine 200 years in the woods of undisturbed ground, no plowing or gardening. If the abandoned place was not in an area of lush growth, like most of mine are not in the poor soil of South Jersey, then most of the old coins, and by that I mean 1700's and early 1800's are found in 4-6 inch range!

If the homestead is in very rich soil, and was abandoned for a long time, with lush vegative growth each year, then it is possible the coins will average in the 6-8+ inch range, all due to more "deposition of soil" and in that case, due to more vegatation growth decaying each year.

As someone stated, open areas, frost can be a factor, but I believe in most areas it does not bury them deeper, just recycles there depth from shallow to not so shallow and back again, a cycle of depth so to speak, not really a main player. Beach sand is a different story if you are talking tidal beaches, of course there anything goes on depth.

But as far as coins sinking in the ground down to 6-8 inches or more, just from the weight and size of the coin, it basically does not happen, again mostly deposition of soil is the main reason.

So, out of my many colonial era coins, I would say my average recovery from wooded, but not heavily overgrown sites are in the 4-8 inch range.

I do agree there is some sinking initially in undisturbed areas, but not much and that the vast majority of depth is from the deposition of new soil.

Again, just think of any Archaelogical dig you have ever seen on TV and basically all artifacts from different periods are in different layers of soil, regardless of the weight and size..........................

Don in SJ

 

[Don in SJ]

Here is some data from an Archaeoligical website backing up what I tried to explain in my first post..

HOW ARCHAEOLOGICAL SITES ARE FORMED

One of the questions most frequently asked of archaeologists is "how do artifacts (or foundations, walkways, etc.) become buried so far underground?" The answer is not that the artifacts sink, but that the ground builds up in layers, or strata, over time. In cross section, the soil resembles a layer cake, with the oldest layers on the bottom and more recent deposits on top. The accumulated layers of soil are the site's stratigraphy.

The accumulation of soil is a natural process that results from the disintegration of organic material such as grass and leaves, and the deposit of blowing dust. Cultural activities also play a role in creating soil layers. Household waste such as ashes from kitchen fires, food remains, and broken glass and ceramics contribute to the accumulation of stratigraphic layers. Activities that move earth around, such as the construction of a cellar hole, have a significant effect on a property's stratification, quickly adding many feet of fill dirt. The more activity that has occurred on a property, the greater the soil accumulation is likely to be.

Why is stratigraphy important? Soil layers are the most basic tools available for measuring the passing of time because the deepest layers of soil are older than the layers on top. For this reason, archaeologists excavate stratigraphically, or one layer at a time, removing all soil from one time period before excavating the layers that preceded it.

Reference: http://www.history.org/history/teaching/enewsletter/may03/archintro.cfm

Don in SJ