Geophysics observation

Normally, I do not hunt inland during the Summer. Being in tropical Florida....... the Summer is exceptionally hot.........and usually accompanied by heavy afternoon rains. This causes grass to be extra tall/thick/fat....... which, in turn..... this fat grass: keeps the coil too high off of the actual ground/dirt. Deep targets are unobtainable with the extra (several inches) of tall/thick/fat grass....that forces the coil to be 'additional inches' off of the actual dirt/ground. Soooooooo........... this presents additional justification as to 'why' I switch over to beach hunting during the Summer months. But.............
this year has been unique. Rainy season (for whatever reasons)..... has been delayed. It has been exceptionally hot. The ground/dirt..... is as hard as a rock. Almost like chipping through brick.

Inland observation: With the ground being kiln-baked by the hot sun....... and no forgiveness from any rain.....,,,,,,,,.........the ground is severely dehydrated.......which causes the dirt to contract/become "more dense" (((subsequently; hard as a brick))). Deep targets become 'less deep' ...... due to the exceptionally high-density dirt being contracted.
Also....... due to no rain...AND extra hot temperatures.,.,.,.,.,.,., the grass is not growing, , , is very brown, , , nearly dead.,.,.,.,.,.,.,.,.,.,.,.,., and almost completely exposing the dirt...... due to its dehydration status.
Sooooooo........ there's virtually no grass: allowing for the coil to be 'on the ground'........................................................... AND..........................................................the dirt is retracted/contracted/shrunk/dehydrated...............causing deep targets to be less deep. (More obtainable). These are two 'wanted' conditions by us detectorists.
In addition to deep targets being more obtainable...........the ground is excessively dry; which causes iron to be 'less activated'. (A third attribute to us detectorists).
In a nutshell................... with the rainy season being delayed.,.,.,.,., I am making some exceptional finds.......inland.

Some years ago (on this forum)..... I explained this phenomenon in the following way: Let's say you have a kids 12-foot diameter plastic swimming pool....with no water in it. A large dry tub. Place that infamous rare coin (say; an old Seated Liberty Dime) ........underneath 9" deep of dry oatmeal in this large tub (kids plastic swimming pool). The 9" deep Dime...is detectable. Now........ JUST ADD WATER! What do you think happens? If you add water to dehydrated oatmeal........ it will 'swell' !!!! Now that 9" deep Dime ...becomes (say) 14" deep; yet, the oatmeal (dirt) only looks mildly 'damp'...........still, with no 'standing water' !!!
This phenomenon also explains ONE of the reasons "why" you may hunt an area AGAIN...... and come away with more 'missed' targets from a previous hunt.

Apply this knowledge accordingly......... to your local geographics/topographics.

NASA Tom, Does the lack of ground moisture also reduce the halo/conduciveness of the deep target? Seems to be a trade off with any ground shrinkage.

Chris

In my experience, deep silver coins are easier to detect when the soil is damp.

That's how block basement walls get horizontal cracks, soil expansion. When the clay soil gets hydrated it expands in every direction, putting pressure on the block walls making them bow inward and forming a crack. Makes sense Tom D. Very important to keep your gutters working properly, especially if you have a basement. Are you finding any good old coins?



Edited 1 time(s). Last edit at 06/26/2022 09:49AM by ozzie.

Chris & Bayard........ I'm not a strong proponent when it comes to 'halo effect'. I believe it to be a lot less than folks suspect. Halo effect has more to do with the 'plume' of leached metal IN the dirt......directly surrounding the extreme close proximity of the metallic object at hand. Usually...... the leached/contaminated dirt that surrounds/encapsulates the metallic object......is NOT a strong enough media for any of today's modern/sensitive detectors to detect. Leave this plume to a mass-spectrometer to sense/detect the leached metal.
HOWEVER; moisture on a target AND the dirt.....will help 'electrically connect' the dirt to the metallic object. THIS will help with bettering the conductivity of the object......so as to be more readily detected by the metal detector. Yes..... this will increase detection range........BUT..........(keep in mind)........if that Seated Dime is now 'electrically connected' to the dirt for better detection; yet, is NOW 14" deep (due to swollen dirt)...........it may simply be out of detection range. (As per example in my [above] post).
ALSO.......... moist ground (as long as it is not too mineralized) helps any/all metallic objects to be detected at further distances; yet, NOT at a linear rate!!! For example: A silver dime can be detected to a greater distance in moist ground (((say: 1.6% better detection))). But something like iron (a rusty square nail).....may present 37% greater detection performance in moist ground. This can work to your disadvantage if you are in a nail/iron-ridden site. Different metallic compositions present different (non-linear) effect.....detection rates.
Also remember........ adding water/moisture to mineralized ground........ is a detriment to detectorists. With moisture: "Lighting up" mineralized ground is a NO-NO!!!
((( Side note: Pure gold does not leach; hence, zero halo-effect. If the gold is alloyed......it is the alloys that will 'leach'. )))

Steve........your question is exactly 'why' I opted to initiate this post! A beat-to-death site (in Deland, FL) has always produced many early wheats (1911 - 1937)..... 1913 & 1914 Barber Dimes...and early Mercury's........... a 1912 "V" Nickel...and plenty of early Buffalo's.......never a quarter!.......and a host of other targets.
BUT.......................recently.......on one hunt: The site produced 7 Indian Heads and 1 Seated Dime (1891). Zero wheat pennies.........in the exact area that used to produce ONLY wheat pennies...and (same-era) other denomination coins. It was as if someone had 'seeded' the dirt with old-generation coins. The depths appeared to be no different (no deeper) than I had been recovering all of the other (early wheat pennies) throughout the years. Only difference/delta: Ground was hard as a brick........dehydrated/shrunk/contracted.

Nice

I guess the hot dry days of summer are more conducive to finding older coins, this bares out for me as both walking liberty halves I have found were during the dry spells in the summer in spots that had been gone over many many times. Both were found with minelab explorers by the way.

Very interesting topic. If you add higher surrounding temperatures it becomes very interesting. Also, coil high at the ground level.

Tom D. The older dates on the new found coins parallels with your phenomena. Would you have observed the shrinking soil effect if the coins you found last were Wheats? Or did the older coin dates clue you into that line of thought?

Steve........ I had a 'hunch' (gut) feeling already; yet, the older generation coins REALLY accentuated the phenomenon. There were plenty of other targets dug also....... of that same era; yet, nearly all trash. It was the 'volume' of targets that I immediately started to recover......... that primarily cued/clued me in. At first....... I thought (and always blame) silent EMI; yet, the EMI conditions were virtually identical to previous hunts at this particular site. And....... the depths of the coins were ALSO in that 9" to 10" range....... which has been the deepest that I have ever been able to ascertain (at best)....... at this particular site.

Tom I know we've discussed this phenomenon over the years here, it's always been a topic of interest.

There are sites that I have observed doing far better (deeper silver coins, deep sounds are more clear, more keepers in my finds pouch, etc) when the ground is damp/moist vs dry.

Out here many of these sites have ground like cement when the ground is bone dry in the summer. I recall hearing good targets at an old Spanish site where the ground was rock hard, it was so hard in fact that I saw sparks emanating from the tip of my shovel when trying to excavate the target. I couldn't dig the targets, the ground was just too hard.

Norm (RIP) of the Golden Olde site swore some detectors were better in dry ground than others.

HH
Mike

Brian.......... Performance is dictated by iron-lateritic soil AND/OR the VOLUME of man-made iron implements......that can dictate HOW much feedback/blowback/flyback from the ground ..... that %-of-water (moisture) will '''activate'''.
I have witnessed (time-and-time again) that moisture will enhance the detection of a silver dime..... UNLESS = higher levels of mineralization and/or: large volumes of iron implements (and especially large volumes of rust flecks/flakes) are ALSO in the 'moist dirt mix'!

Mike_Hillis Wrote:
-------------------------------------------------------
> Norm (RIP) of the Golden Olde site swore some dete
> ctors were better in dry ground than others.
>
> HH
> Mike


Yes he is correct as CZs are better in dry ground as nails do not leach into the ground as much and cause falsing.
The Whites DFX and XLT I had was the opposite as preferred moist soil it seemed.

NASA-Tom Wrote:
-------------------------------------------------------
> Brian.......... Performance is dictated by iron-la
> teritic soil AND/OR the VOLUME of man-made
> iron implements......that can dictate HOW much fee
> dback/blowback/flyback from the ground ..... that
> %-of-water (moisture) will '''activate'''.
> I have witnessed (time-and-time again) that moistu
> re will enhance the detection of a silver dime....
> . UNLESS = higher levels of mineralization and/or:
> large volumes of iron implements (and especially l
> arge volumes of rust flecks/flakes) are ALSO in th
> e 'moist dirt mix'!

That makes sense. I have a few heavy alkali desert type sites, and when the ground is wet/damp/moist, it's effectively like hunting a wet salt water beach. When I had my Impact at a particular site that had moist alkali soil it couldn't auto ground balance, but manual worked fine. It balanced the same as a wet sand ocean beach. I found that beach modes tend to work well at these types of sites for me.

There are quite a few places in Florida...... that are far from the beach..... that presents 'brackish water'.....hence; brackish dirt!!!.......and......... it is mandatory to use the "Salt" Mode and/or Ground Balance for the salt.

I hadn’t even thought of that Tom. I’ll bet I would have done better using salt/ground balance in some of those places. Great observation.

Gary........anywhere close to St. John's River is one example!
(((You will also notice major salt corrosion on recovered targets))).

Tom you say a square nail has the ability to have a 37 percent better return when the ground is moist.I have a ? what are the return ratios for a nail the same size on top of the ground compared to that same nail fused with halo in the ground i am thinking the nail in the ground well have a larger signal . sube



Edited 2 time(s). Last edit at 06/30/2022 03:54PM by subey.

subey.......... Yes. A nail (or ANY metallic target) on top of the ground will most certainly present the STRONGEST signal......... as compared to the same target that is several inches deep.
Another example: A coin on the surface of the ground will give maximum signal-strength......... compared to the same coin (say) 5" deep.,.,.,.,., regardless of moisture level(s) in the surrounding dirt.

I guess i did not word that right . 2 nails same size 5 inches deep fresh buried 1 nail no halo second nail same depth but in the ground with a halo .
What I am asking is the nail with halo orange rust around it have a bigger return than nail without halo .wet or dry conditions.
The reason I ask is I have 10 nail coin combinations buried in my test garden all coins were detected when buried after 4 years only 6 were detected at 6 years only 4 were detected and after 10 years 2 were detected. After a good rain i did not detect as many as dry conditions but over time I am detecting less and less. sube



Edited 2 time(s). Last edit at 07/01/2022 02:12AM by subey.

subey.........ok......... I understand your question now.

Yes. There is a certain percent BETTER detection of the rusty nail.......in moist ground...that has been there for 100-years. , . , . , . , . , . as compared to a freshly buried rusty nail in dry dirt (at the same depth).,.,.,.,., AND.....to include: in (equivalent) moist dirt.
The 100-year buried nail (with subsequent halo) ........ has a: better 'connect' with/to the immediate surrounding dirt.......and NOT so much to do with the rusty blood-stain, oxidized 'halo' that is surrounding/engulfing the nail.

(((Did I 'finally' answer your question)))?

Yes you did Tom and thanks .sube

Tom, in the same vein, I've considered the effect of moist vs. dry soil on the final resting state of nails (and coins). The horizontal position is the most stable end-state of a nail in soil (offers the greatest resistance to further displacement). Most nails are therefore more or less in the soil matrix in a horizontal position, as they were when dropped and subsequentially buried by soil overburden. A vertical nail at depth would indicate the soil at some point experienced mixing of some form: by liquefaction during the rainy season, or flooding, by natural mechanical forces (e.g., growing tree roots, worms, ice heaving), or by man-made mechanical mixing (digging or tilling of the soil). At some point over many years, a nail would sink in porous soil beyond the reach of these kinetic actions, say beyond 12" or so. So, a ratio of more shallow horizontal nails would indicate an area where no recent soil turnover has occurred. A deep horizontal nail and shallow horizontal nails would indicate perhaps many decades or a century of undisturbed soil.

It is assumed that coins would also tend to be found more horizontal than vertical, but if vertical at depth there was some randomization of the soil matrix in the past. A corollary thought here is that densely compacted soils may be indicative of little mechanical turnover and the expectation is that the greatest depth where nails substantially are horizontal indicates the approximate age since soil turnover. In other words, a mixed nail matrix to 6" and then mostly horizontally aligned nails at deeper depths would indicate a more recent mixing event. A hard-packed soil with vertical nails (or coins) present in summer would indicate turnover is still occurring during the winter/rainy season. The depth of the turnover relates to the soil type and regional climatology among other things. All things being equal, an old horizontal nail dug at 14" (or coin) likely survived its descent to that depth during a period where the ground was left fallow for perhaps several decades (that is, a half-century ago it was allowed to sink undisturbed and is now beyond more recent mechanical mixing actions).

John.......... well founded thoughts.

What I have experienced in my locale ........ especially with the advent of EQX with it's fairly large 11" coil......is............ there is no ratio differential between 'flat' coins, 'tilted' coins and coins 'on-edge'. I am finding coins at any random orientation. Infact........ the 11" DD EQX coil has accentuated the recovery of 'tilted' and 'on-edge' coins. This also holds true for nails ...and their respective orientation to gravity. ANY random angle/tilt/orientation ....... is the 'norm'. Many detected areas are heavy foot-travel areas......... some areas have zero human habitation/travel. It would be logical that 'turned/disturbed' dirt would cause this phenomenon; yet, plenty of data exists on behalf of the contrary.

There is a correlation of: high foot travel areas...... causing deep targets to become more shallow.....due to compacted/compressed (beaten down) dirt.

There is an area where I live where coins a particularly shallow. I have hunted four yards in close proximity to one another where the oldest coins were only 3-4" max. I was finding V nickles and IHP's, and a Barber dime just 3" inches deep in a couple of these yards. Most silver here is much deeper. Some so deep it's just a whisper. I have found no rhyme or reason for the some shallow and some deep at these places because soil composition is the same. I've also hunted many yards with for sure fill on them. For some reason these are in variably a bust even though I know the fill should not have put the coins out of reach.

NASA-Tom Wrote:
-------------------------------------------------------
> Chris & Bayard........ I'm not a strong proponent
> when it comes to 'halo effect'. I believe it to be
> a lot less than folks suspect. Halo effect has mor
> e to do with the 'plume' of leached metal IN the d
> irt......directly surrounding the extreme close pr
> oximity of the metallic object at hand. Usually...
> ... the leached/contaminated dirt that surrounds/e
> ncapsulates the metallic object......is NOT a stro
> ng enough media for any of today's modern/sensitiv
> e detectors to detect. Leave this plume to a mass-
> spectrometer to sense/detect the leached metal.
> HOWEVER; moisture on a target AND the dirt.....wil
> l help 'electrically connect' the dirt to the meta
> llic object. THIS will help with bettering the con
> ductivity of the object......so as to be more read
> ily detected by the metal detector. Yes..... this
> will increase detection range........BUT..........
> (keep in mind)........if that Seated Dime is now '
> electrically connected' to the dirt for better det
> ection; yet, is NOW 14" deep (due to swollen dirt)
> ...........it may simply be out of detection range
> . (As per example in my [above] post).
> ALSO.......... moist ground (as long as it is not
> too mineralized) helps any/all metallic objects to
> be detected at further distances; yet, NOT at a li
> near rate!!! For example: A silver dime can be det
> ected to a greater distance in moist ground (((say
> : 1.6% better detection))). But something like iro
> n (a rusty square nail).....may present 37% greate
> r detection performance in moist ground. This can
> work to your disadvantage if you are in a nail/iro
> n-ridden site. Different metallic compositions pre
> sent different (non-linear) effect.....detection r
> ates.
> Also remember........ adding water/moisture to min
> eralized ground........ is a detriment to detector
> ists. With moisture: "Lighting up" mineralized gro
> und is a NO-NO!!!
> ((( Side note: Pure gold does not leach; hence, ze
> ro halo-effect. If the gold is alloyed......it is
> the alloys that will 'leach'. )))
>
> Steve........your question is exactly 'why' I opte
> d to initiate this post! A beat-to-death site (in
> Deland, FL) has always produced many early wheats
> (1911 - 1937)..... 1913 & 1914 Barber Dimes...and
> early Mercury's........... a 1912 "V" Nickel...and
> plenty of early Buffalo's.......never a quarter!..
> .....and a host of other targets.
> BUT.......................recently.......on one hu
> nt: The site produced 7 Indian Heads and 1 Seated
> Dime (1891). Zero wheat pennies.........in the exa
> ct area that used to produce ONLY wheat pennies...
> and (same-era) other denomination coins. It was as
> if someone had 'seeded' the dirt with old-generati
> on coins. The depths appeared to be no different (
> no deeper) than I had been recovering all of the o
> ther (early wheat pennies) throughout the years. O
> nly difference/delta: Ground was hard as a brick..
> ......dehydrated/shrunk/contracted.

An extremely compiled bit of thought-provoking information that is spot on. I can personally say I've never, ever conceived this type of analysis of in ground targets. Thanks Tom.

Longbow....... I wished I could lay eyeballs on your site(s)....... so as to see what your conditions are. I too.....have found sites whereby: the old coins are only a few inches deep; yet, here in wet/boggy/soggy/tropical Florida...... shallow old coins are either from where erosion has taken place.........excavation........... sidewalks lifted......... or highly compacted dirt (that has also become very inorganic)........ to cause old targets/drops to be shallow. (There is always a reason/justification).

Mark.......you are welcome. I'm glad there still remains a few folks of whom appreciate my 'scientific-approach' data!

this is a very interesting topic ... thanks
Two summers ago, here in NY we received zero rain for the whole summer ... the grass dried and most of the areas that were once grass lawns became dirt ... I had asked a few others of my observation that my detector works better in dry dirt than wet ... this was due to the fact of finding very deep fatty indians and shield nickels, along with some older silvers ... I thought this was due to the fact that the small bits of iron no longer responded as they did when the ground was wet, unmasking so to speak ... one person suggested the iron in the grass may also make a difference ... last year we had a pretty steady rain fall ... my silver count went way up, nickels and fatties went way down ... this year we are back to the "no rain in sight" mirror of two summers ago ... my soil is not the concrete hard soil like you are speaking of ... the organic layer to about 6 inches is somewhat hard, but after that the ground is powdery ... more open and less dense than when wet ... pop the pug and you can sink a spade with no effort, unless a rock is involved. ... I guessed that if the organic layer was removed the resulting powdery layer would be as close to an air test as one could hope to get, and once the grass was gone, I gain an extra inch by running the coil right on the dirt.

Scraping off the topsoil/organic layer..... would present multiple surprises.