Tennessee Crater Inches Toward Recognition 113
tetrahedrassface writes "Slashdot carried the story of an-as-yet unverified impact crater in Tennessee a couple of years ago. After a few weeks of fairly hardcore sample taking, digging, obtaining some good images and manipulating them, I'm proud to report the first batch of evidence in favor of it being an impact site. The primary smoking gun is the presentation of an astrobleme, obtained from High Resolution Ornithographic Images taken in 2008. Also of note are the melted/deformed rocks, magnetic crater dust, and the fitment of the crater rim to a circle. A rented plane and a bunch of photographs today and it's pretty obvious that it's a crater, folks. Cheers!"
Re:Pride?? (Score:3, Insightful)
He's not proud of the crater, he's proud of all the work he's done to verify that it's a crater. Learn to think before writing and the quality of your post will increase dramatically.
Re:Pride?? (Score:5, Insightful)
Re:Gee, amateur science (Score:5, Insightful)
I'm a professional scientist with a pile of published papers, and I'm here to say that amateur science is a very good thing. Who are we to tell young Calvin to turn off his inquisitive mind when he hits puberty? The guy who wrote TFA is a *far* more interesting person than the people who're mocking him.
Now, do I believe that he's right, and this *is* a crater? Nope. I suspect it's wishful thinking. Does his work meet the standards of peer-reviewed scientific literature? Definitely not. Does his work meet the standards of Slashdot? I dunno, does Slashdot have standards? All I can say is I'd rather read articles like this than the Apple flame wars or hackneyed political debates that fill the rest of the news feed.
Re:Were you able to exclude karst? (Score:4, Insightful)
I fully intend on getting thin sections done. The gravel IS angular. There are heavily deformed Ordovician Age rocks. Unfortunately, where this area is a Karst area. You can't pick up the feature and move it to an area that makes it easier. Is this a Karst feature? I doubt it very seriously. However thin sections for shocked quartz are next on the list. I appreciate the time you took to reply. No topsoil was never pushed into the middle of this feature. Yes, a road was cut in pushing regolith into one corner and making it look a lot squarer than it is. I know the full history behind the site going back over 120 years. There is rounded material i.e. (sand) in the soil around the crater at a microscopic level because the soil is 200+ million years old and already contained HEAVILY WEATHERED ancient rock..
The investigation continues. Thin samples of severely deformed rocks are next.
Re:Were you able to exclude karst? (Score:2, Insightful)
I wouldn't worry too much about the squarish shape. It's close enough that I don't think the shape in map view is an obstacle to it being an impact crater, especially if it has experienced weathering. You mention Barringer Crater [wikipedia.org] which isn't perfectly round either, and that's a fair analogy. However, all the other issues mentioned still stand. There are an awful lot of ways to make a roughly-circular pit in the bedrock geology, especially in a karst area. Generally speaking, if we were on Mars or the Moon a crater interpretation for a roundish structure is probably the default, and other possibilities get considered only after excluding a crater interpretation. But on Earth, impact craters are rare because there are so many other processes going on. You pretty much have to exclude all those other processes first, or find something definitive such as the high-pressure phases of quartz (e.g., stishovite [wikipedia.org]), impact melt [wikipedia.org] (more to it than just "melted rocks"), shocked quartz (although there are other ways to make it), etc. Even then the case can be hard to build up.
If you want an example of just how hard making the case for an impact can be, even when you've got a structure that's "obviously round like a crater", check out the history of Upheaval Dome [wikipedia.org] in Utah. The arguments over that structure date back many decades, and it is especially tricky because a salt diapir interpretation is quite plausible (there are salt deposits in the area). I've seen the structure myself. Even standing on the edge of it, I wasn't convinced it was a crater. But apparently it is, albeit a deeply-eroded one (we're sort of looking at the deep structural deformation beneath the crater rather than the original bowl-shaped depression).
Keep at it, but be aware that you're going to have to expand your understanding of regular geological features too. If you are unfamiliar with what's "normal", geologically-speaking, it's pretty hard to tell what's "anomalous". It might be helpful to go some distance away from the proposed crater and sample some of the same Ordovician target rocks that you are confident are outside the area expected to be affected by the possible crater -- i.e. calibrate your interpretations with something that isn't impact-related. Then you can compare.