The Story of My As-Yet-Unverified Impact Crater 250
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."
Sinkhole sounds plausible; impact crater not. (Score:4, Informative)
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.
Cut it! (Score:5, Informative)
Cut the stone with angle grinder, polish the cut, show us the picture. Meteorites have quite distinctive texture.
Carbonates (Score:5, Informative)
[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.
Sinkhole (Score:4, Informative)
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.
Have studied Geomorphology (Score:5, Informative)
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.
Re:Looks like a karst depression (Score:2, Informative)
When you say "react with", you mean "dissolve, usually quite slowly, in".
Sorry, that is not what he means. Most carbonates will react (not dissolve) with chlorinated tap water and acidic ground water.
Re:Cut it! (Score:4, Informative)
As someone posted earlier, "Jamie Want Big Boom."
Meteorwrongs (Score:5, Informative)
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!
Maybe yes, maybe no, hard to say from here... (Score:4, Informative)
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
Re:never heard of metorites reacting with water (Score:2, Informative)
Not so, the alkali earth metals (calcium, for example) will also react with water on a clean surface, but much less violently. Calcium still evolves gas at a visible rate...
Re:Cut it! (Score:4, Informative)
Maybe he should cut it with a cut-off wheel instead of a grinding wheel, unless his goal is to produce sand.
Personally I use a miter saw with a grinding wheel to cut stuff that isn't wood, so I don't have to hold anything steady.
Acids vs. bases (Score:3, Informative)
> 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.
Re:It looks like an impage crater... of sorts (Score:4, Informative)
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 can help you with determination (Score:2, Informative)
Re:never heard of metorites reacting with water (Score:4, Informative)
If he was holding it in a frangible container 6 inches from his face with no protection while submersing it in water, then yes...he could get injured by an Alkali metal. They actually react quite slow in comparison to many other explosives, and have a very limited amount of power. In fact, several grams of Sodium wasn't even enough to break a soda bottle for me. It just filled with some nasty smoke/gas and distended the bottle.
Also, take into account that if he just found them lying there, there is almost zero chance they are alkali metals. They would long ago have disappeared thanks to rain and atmospheric humidity. A simple carbonate is the most likely answer.
Jesus. (Score:5, Informative)
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!
Re:Have studied Geomorphology (Score:2, Informative)
I'm not from USofA and thus have no idea if You will need to $$ to get it.
You don't always need to pay for a topo map. They can be found online here [msrmaps.com] for free. I use these at work all the time and they are decent if not really out of date sometimes. All you need is the coordinates (can be had from google earth or maps).
Also I agree with previous poster RWarrior(fobw) it is probably a ferrous carbonate such as siderite or something similar and you have most likely found a sinkhole. Now if they are uncommon in your area you may have something special there.
Re:Carbonates (Score:2, Informative)
Re:Have studied Geomorphology (Score:2, Informative)
Most US Geological Survey 7.5 minute quads are available for download in PDF from: US Topo [nationalmap.gov]
With the size the OP mentions, it should show fairly well; these are 10 foot/3 meter contours and a 1200 foot "crater" should be about 0.6"/1.5 cm. Not all states are covered, yet, but there are other free USGS sources to download these.
Re:Sinkhole sounds plausible; impact crater not. (Score:2, Informative)
"new-metal" looks like a blob of zinc. Perhaps an outbuilding was in that location and burnt down? I've seen a lot of zinc-head nails, and a haymow burning would melt all the zinc on top of a corrugated roof sending it down in rivulets to solidify on the ground.
It's really hard to take you seriously when you talk about the "vibe" of the place. That says you've already decided to believe things not in evidence. That greatly reduces your usefulness as a source of information.
Re:Jesus. (Score:4, Informative)
I don't know where you got the idea that there haven't been meteorites (meteor remains) found at Meteor Crater. There have been, thousands of fragments, totalling over 30 tons [wikipedia.org], collected from the region, including a 600kg specimen.