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The Story of My As-Yet-Unverified Impact Crater
tetrahedrassface writes "When I was very young, my dad took me on a trip to his parents' farm. He wanted to show me 'The Crater.' We walked a long way through second generation hardwoods and finally stood on the rim of a hole that has no equal in this area. As I grew up, I became more interested in The Crater, and would always tell friends about it. It is roughly 1,200 feet across and 120 feet deep, and has a strange vibe about it. When you walk up to it, you feel like something really big happened here. Either the mother of all caves is down there, or a large object smashed into this place a long, long time ago. I bought aerial photos when I was twelve and later sent images from GIS to a geologist at a local university. He pretty much laughed me out of his office, saying that it was a sinkhole. He did wish me luck, however. It may be sinkhole. Who knows? Last week I borrowed a metal detector and went poking around, and have found the strangest shrapnel pieces I have ever seen. They are composed of a metal that reacts strongly to acids. The largest piece so far reacted with tap water and dish-washing detergent. My second trip today yielded lots of strange new pieces of metal, and hopefully, one day the truth will be known. Backyard science is so much fun. And who knows; if it is indeed a cave, maybe Cerberus resides there."
I'm kindof afraid that your backyard is going to become the first physical place to be slashdotted.
Why does this remind so much of The Story of Barbie Head Archeology...
Could be a karst landform http://en.wikipedia.org/wiki/Karst_topography. Carbonate rock will react with water.
my guess is that you have something along the lines of calcium carbide in those rocks
Beware the Jubjub bird, and shun the frumious Bandersnatch.
How about taking a bit down to the geology department at the local university? Find out what the crater actually is. It could be important :)
are you (my fellow /.ers) sure this isn't a stalking horse for some kind of viral advertisement / alternate reality game?
Looking at that photo, sinkhole sounds plausible.
Maybe there are more holes in the surroundings, then it's clear. Also don't craters normally come with an elevated rim? Hard to see from above of course but no indication of such a rim around it.
Oh well lots of guesses will be posted here I'm sure. It's /. after all, fantasies running wild.
Indeed just take those metals to your local uni or so, have them figure out what it is. If they really react strongly to water then this must be recently exposed material (won't last long outdoors in the wet soil), so can't be from an ancient impact crater. I mean the material itself could be from whatever source but it's obviously exposed recently as you can find it easily with a metal detector so can't be there for a very long time or it would have weathered already.
Also impact craters usually have lots of glassy material from molten rock present, look up some research articles about confirmed craters on what you should be able to find there.
You know why he laughed you out of his office? Because you went in there saying "Look! I've got an as-yet undiscovered crater in my backyard! Or maybe it's a big cave or something!"
It makes you sound like some easily-impressed idiot who doesn't know the first thing about rocks, which is probably what you are - something that irregular and in soil that looks that soft is almost certainly not a crater. I mean, just compare it to a picture of an actual crater; they're nothing alike.
And then you go off about "oooh when I put water on these rocks they bubble!", like you've never heard of limestone (and it sounds like you probably haven't), and "I found weird lumps of metal!" like you've never heard of (oh I don't know) humans leaving shit around.
Seriously, you sound like the worst sort of credulous idiot. There's a reason why they say "ten hours in the lab will save you an hour in the library" - do some reading up on even the most basic geology first (and I mean fucking basic, not the awesome stuff like impact craters or mega sinkholes or what have you), then start telling people about how awesome it is. I'm sure that formation is, actually, very interesting - you don't get areas with (apparently) a lot of water and a lot of limestone without at least some neat stuff happening - but you don't need to start by making shit up!
Cut the stone with angle grinder, polish the cut, show us the picture. Meteorites have quite distinctive texture.
[My apologies for the lack of links: Google is your friend. The editor is being a bitch.]
If it reacts with acid, it's carbonate (such as calcium carbonate, CaCO2). The classic test for carbonates is to dump a 5% solution of HCl (hydrochloric acid, available as muriatic acid in any hardware store) onto the sample; if it bubbles, it's a carbonate. (I know one geologist who calls this test "barbaric.") You can also use common household vinegar.
99.99% of all carbonates on the Earth are sedimentary. Usually, they form in shallow to medium depth water when microscopic critters with calcium shells die by the kazillions and fall to the ocean floor, where they pile into layers that give us things like limestone. There is one exception, however: Oldoinyo Lengai is a volcano in Tanzania that produces carbonate lava (the only carbonate-producing volcano in the world -- all the rest produce silicates, products based on SiO2). Someday I would like to see a sample of this igneous carbonate, because while silicates are really really important in geology, they're also really really common, and thus really really boring.
A relatively inexpensive bulk chemical analysis could tell you the exact composition of your samples, and you would probably find a pretty high iron content, which accounts for the trigger on your metal detector. My educated guess is the mineral siderite, FeCO3. It is common both in hydrothermal veins and in sedimentary formations.
Sinkholes can form when subterrainian water flows dissolve minerals (such as carbonates), forming a cave that later collapses. When this happens, you get a crater. And yes, you can get a pretty big one, depending on how deep the cave is.
So yes, it's a probably a sinkhole.
Remove the caps and hold to a mirror.
Speaking as a caver, it could well be a shakehole (sinkhole). It's not the classic shape for it but they vary in shape and size. It's big, but not enormous. If it is a shakehole it certainly won't have broken any records.
As a first step, check some geological maps. If you're above limestone, I'd say: case closed, it's a shakehole. Yes, it's above a cave (or at least where a cave used to be!) The first photo of the "new metal" looks suspiciously like limestone.
Finding out a origin of such negative relief forms is a hard task.
1) Get a fine scale topographical map of it's surroundings. 1:10'000 is excellent, 1:25'000 could also work (depends on crater size). Look for any similar features around. Could this be a simple erosional form?
2) Go to nearest geological survey department and ask for surface geological map. Depending on Your location, it might be called "Quaternary sediment cover map". I'm not from USofA and thus have no idea if You will need to $$ to get it. If they offer also an geomorphological map, take that also. Those maps will help You to understand locations geological setting. You will be able to check possibility of ordinary karst or termokarst.
3) Compare craters location with known extent of Quaternary glaciations. In territories with Quaternary glaciations or close to glacial limits is possible to see termokarst depressions. They can be of variable size and form - starting from small, round crater-like forms up to large wally-like depressions filled with modern lakes.
4) If You want to describe any rock sample, You need to get a clean, fresh surface. Identifying rock samples by simply pouring an acid on it's surface might just reveal presence of calcite in soil and say nothing about rock it self.
5) Double check exact location in relief where You found those sock samples. Could there been some springs coming out or have been groundwater discharge location? Then it might be Limonite (bog ore) http://en.wikipedia.org/wiki/Limonite
6) If it's still not clear what it is - get an hand auger (soil sampler). I use One-Piece Edelman Auger. Make a profile line over that "crater" - sample on undisturbed land, on the rim, at the bottom etc. Get coordinates for exact location; photographs; describe color, wetness, anything You see or feel with hands (pebbles, sand, dust). Making correct description sill might need an training to get familiar with methods, still You will be able to tell if there's difference in soil composition on rims/bottom in comparison with surrounding territory (if crater is young enough).
Sorry form my language.
Why are you using abusive language to a complete stranger, just because he doesn't know as much geology and chemistry as you do? Perhaps you should think about attending a course on anger management.
From scarped cliff or quarried stone she cries "A thousand types are gone, I care for nothing, no not one."
We get these sorts of questions regularly on my site (www.mindat.org) and, I have to say, the vast majority of times they turn out to be of entirely terrestrial origin (meteorwrongs).
A friend at the Natural History Museum in London tells me that well over 99.9% of the items brought in as possible meteorites turn out not to be. The chances are not good.
Now, I would not want to dismiss your findings out of hand because, of course, meteorites can be found anywhere. But the first picture doesn't look like a meteorite to me at all. It looks like a very badly corroded iron pyrite nodule, which are relatively common in some limestones and other sedimentary rocks. The second one could be a meteorite, but it could equally well be a nodule.
Easy way to tell is break one open. If it has a radial crystalline structure then it cannot be a meteorite, it can only be an iron sulphide nodule.
Alternatively, post pictures and descriptions on my board where real geologists and mineralogists can help you!
Jolyon
ps. Calcium Carbide? I had to laugh!
Please read my Canon EOS tech blog at http://www.everyothershot.com
It could easily be a meteor crater or a sinkhole, or even an old quarry (depending on the quality of the rock). If it is a meteor crater that size, you really have hit the jackpot, because meteors are worth money. However, the people who buy them aren't idiots, so you won't make money pretending; you have to find out. If it was formed by a meteor, there would have been splatter in all directions, but more in one direction than the others. Get a metal detector and search not just inside but all around the periphery up to three or four hundred meters away. If it really is from a meteor, and nobody has "mined" out the many fragments it would have produced, and it was the right kind of meteor (many are nickel-iron, some are stony, nickel-iron are the ones you can find and identify with a metal detector) you will find some chunks that aren't just teensy bits, but are large, partially fused, chunks of mixed iron and rock. They are hard to miss -- their density is close to twice that of ordinary rock (specific gravity closer to five than three). As another poster pointed out, even stony meteors can usually be identified by sawing and polishing -- the origins of meteor rock are typically quite different from earthbound rocks and they have a characteristic structure. But limestone chunks are probably not going to be meteors...;-)
Anyway, if you have a real crater with lots of real meteorite fragments, bear in mind that they will sell for hundreds to thousands of dollars each, depending on size, composition, and provenance. Even tens of thousands for large bits. And yes, there are geology departments at Universities that would like very much to help you search for pieces and study the crater itself, and you should give them first dibs before making money out of it as knowledge is more important than money.
Good luck, but don't hold your breath. No matter where you are sitting, you are sitting on top of at least meteor dust as a contant rain of that drifts down from the sky every day, and fragments from tiny to small are rather commonplace. Larger fragments are increasingly rare, though, and really big impact craters (that have been identified as such) are very rare.
rgb
Even when the experts all agree, they may well be mistaken. --- Bertrand Russell.
> They are composed of a metal that reacts strongly to acids.
>The largest piece so far reacted with tap water and
> dish-washing detergent
Dish washing detergent is basic, not acidic.
http://ca.answers.yahoo.com/question/index?qid=20090106114510AAlzSKE
It is highly unlikely you have a single material that reacts _chemically_ the same way to both.
An impact crater look very differently from what happens when you toss a coin. Hint: there's a *BIG* explosion when the kinetic energy is suddenly transformed into heat.
No matter how shallow is the angle, impact craters are always nearly circular and symmetric. The material is suddenly compressed with a huge amount of energy and heats up to thousands of degrees. The resulting explosion propagates to all directions, independent of which direction the meteor came from.
I'm an undergrad student of Chemistry and I live in a karstic region, so I might help you a bit. First it would be cool if you would measure the density of the potential meteorite (displacement of water + mass, measure first mass) and also it would be nice if we could determine for example the amount of iron in it This can be done with common household chemicals (HCl, NaOH both common available accross the globe). Iron is not so rare in such karstic landscapes (if that crater is in one), but afaik is usually not in an elemental form. You used a metal detector so you've probably found a metallic element. That's also judging from a second photo from comments, where we can see the shiny metallic lustter. Also you could maybe give me your email or something ;)
This is not in Florida... And no, I won't post lat and longitude because I can see that a lot of people would probably swarm out here. I will continue detecting around the area, looking for more pieces of metal, and maybe even, god forbid go down in the bottom and dig.
For all the constructive posts, thanks. If it is a cave, I want to go in it!
I suggest you take a Geiger counter with you on your next trip to the crater before you go mucking about too much there.
9/11 Eyewitnesses to Explosive WTC Demolition 1 of 2
The thing is that on Slashdot no one knows how old you are.
If this poster is 14 or 15 he may be on the start of becoming a very good geologist.
Even 18 he still is just really enthusiastic.
I agree this is probably a sink hole of some kind and not an impact. But that is only a guess I have only a passing knowledge of geology but none of the rocks shown seem all that odd to me.
You never educate through ridicule and for all you know you just made some 16 year old girl just getting into science cry.
See my blog http://ilovecookes.blogspot.com/ for light hearted technical information.