Thinking About A Sinkhole

[KarstRanger]

So I live near the suwannee river in FL and there is this old sinkhole not far from my property. It is about 500 feet from the river and is on some vacant land and is about 30 ft. across and 3 to 5 feet deep. There are 50 yr. old trees in it but that is the age of trees in all this area, and the remnants of an old cypress, so it not a recent sink -- but hopefully it is much older.

Is there a way to pound a 3" pvc pipe or something like that down into the ground and see if this just might be an ancient sink hole? Any ideas other than a back hoe would be welcome.

[Auspex]

Pounding PVC into the ground sounds like a frustrating way to not make a hole. I'd try sterner stuff at least, and still not have high hopes for the desired outcome. The question isn't whether there's a sinkhole there, but whether it has collapsed and/or filled. Is good old fashioned digging out of the question? Even a post hole digger would at least allow you to sample the fill to some depth.

[PrehistoricFlorida]

I wouldn't waste my time with it... stick to finding sink holes with water in them.

[Guest solius symbiosus]

If it is a sink, it is definitely ancient. The amount of time that would be required to dissolve the limestone would dictate antiquity.

[PrehistoricFlorida]

No, we have plenty of recent sinkholes. Several new ones form each year.

[Guest solius symbiosus]

I would think that the sink would have to be there, and then the regolith is eroded away. Dissolution of limestone is accomplished by weak carbonic acid in rain water that forms as it falls though the atmosphere.

[Guest N.AL.hunter]

Many a great find has come from old sink holes and old river channels/oxbow bends that can be seen in remote imaging pictures. The question is how deep would you have to dig? It could be very deep and practically impossible to do manually. If real curious, you could try to dig a post hole or drive a 8' long grounding rod into it to see if you hit something solid within that depth. I wouldn't use the PVC.

[KarstRanger]

In talking to local farmers, it seems the sinks we have around here are usually a collapse in the roof of an underground aquifier chamber of some type, and they tend to be dry and just a pit (that I hope would collect bones over the years). There is one sink nearby which I understand is called a karst window, named Cow Springs near Luraville which some of you divers may be familiar with. It is a deep sink full of clear spring water with no surface outflow, and is like a hole in the top of an underground river.

I will try the ground rod idea and see if I hit anything. I am worried I won't get deep enought, however, as the local power company was regrounding their power poles here last summer and they said that they had to go down through about 30 ft. of sand to properly ground the poles into limestone. Stay tuned