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Dear Jackie: When they got Glacier Girl out, she was taken to Middlesboro, KY. Did you know KY has three "astroblemes"? One is near Middlesboro,Bell county.
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Carpal Tunnel
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Hi, Dr. Bill--no, I don't even know what an astrobleme is.
And stales, perhaps you can help me here, or you, CK--I'd had the idea that a chimney (vertical, narrow, yup) was something that was formed naturally--usually in rock. But I thought the fact that it was dug would qualify the opening down to the plane as a shaft. Otherwise, why don't we say, "going down the mine chimney"?
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Carpal Tunnel
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The idiot also known as Capfka ...
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Carpal Tunnel
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Dear Jackie: I thought you'd never ask! An "astrobleme" is a "star wound" where a large meteorite hit the Earth long ago, leaving an elevated ring around a crater.
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Carpal Tunnel
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Happy to oblige, Mr. Pronounces-his-t's-half-the-time!  "Star wound" = "astrobleme" = star blemish, right?
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old hand
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old hand
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A chimney in the non-building sense is always a natural feature. However, one can use the climbing technique of "chimneying" to make one's way up or down a man made structure.
A mine shaft is a vertical or subvertical opening used for transporting people, equipment or rock to and/or from the surface. The term is often used incorrectly in reference to a horizontal or subhorizontal tunnel opening out onto a hillside. The correct term is adit, the opening of which is the portal.
Horizontal tunnels throughout a mine are referred to as drives.
A couple of special case of shafts are winzes and raises (or rises, depending where you're from). Both words, like chimney, can be used as a noun or a verb.
A winze is a shaft developed (ie excavated) downwards from a drive - it is not open to the surface.
Similar deal with a raise - only it is developed upwards from the back (ie ceiling) of a drive. Purists will take exception to this because raise boring machines actually develop the raise from the top down. A mere technicality, the hole is still called a raise. Raises may be developed through to the surface, particularly if they are to be used for ventilation (hence vent raise) and/or if they are to be used as an escapeway.
stales
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addict
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You're just loving this thread, aren't you? 
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Follow me on the subject of this post? wwh suggested off board I give "astroblemes" the treatment.... I am fortunate to be friends with Drs Jenny and Alex Bevan - wife and husband - and curators of the UWA E de C Clarke Geology Museum and The Minerals and Meteorites department of the Western Australian Museum respectively. A quick call to Jenny helped answer to a very good question from wwh - namely, "How can one calculate the size of the celestial body that created an astrobleme from the size of the crater?It seems that the answer isn't simple, the crater's size depends upon a number of variables (see green text below). Frinstance, Jenny said that the Hoba meteorite, a 60 ton lump that landed in Africa, left no crater. Jenny's emailed reply was as follows: This is a useful page:
http://seds.lpl.arizona.edu/nineplanets/nineplanets/meteorites.html
The diameter of a crater should vary with the cube root of the mass of the impacting meteorite times its velocity squared, but it will depend on the nature of the body and impact site and angle of trajectory.
Impact craters less than 1cm across are found on other bodies in the solar system and are called microcraters (not on Earth, meteorites this size burn up in atmosphere).
Impact craters larger than 300km are called impact basins (again, not on Earth because they date back to early times and Earth processes have obliterated them)
Earth processes work on craters of all sizes to obliterate them. eg. a crater 20km across will be recognisable about 600 million years, whereas craters 1km across will only be recognisable for say 1 million.
An ASTROBLEME (= "star wound") is the eroded remant of an ancient impact crater eg Goss's Bluff. We tend not to use the term once we are sure about it having been a crater, and just say that it is an eroded and/or buried
crater etc., which is probably why you couldn't find a definition easily.I've checked through the site mentioned above and found it chock-full of good info. I also found a site dedicated to the Barringer Crater in the US but didn't note the URL.  It's interesting because, in the early 1900's, Mr Barringer basically did his shirt drilling the base of the crater to find and exploit the fabulous wealth of nickel, iron and diamonds he presumed lay buried. He did not take the news provided by a ballistics expert very well. This chap's experiments showed that any sizeable body travelling at cosmic velocity is completely unaffected by our atmosphere - but totally destroyed the nanosecond it impacts the Earth's surface. So Mr Barringer was looking for something that wasn't there. stales
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old hand
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doc - am I so transparent? I just hope others are enjoying it as well. Tis a sad day the day one doesn't learn something. Rest assured, I'll pipe down when I hear the moderator's bell!
Besides, it takes my mind off the cricket. [tag for CapK and Max e-]
This thread is just like my mind...full of words and ideas, interested, interesting, many themes, a bit of adventure etc!
stales
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Dear Stales: thanks for the link, which I will have to study. One more question. There have been a number of studies on very large methane hydrate deposits on seafloor reported on Internet. When I saw map of Chicxulub crater on Yucatan extended well out into Gulf of Mexico, it occurred to me that a very large amount of sea floor methane hydrate could have been vaporized and ignited, contributing a very large amount of energy to the impact. I sent an e-mail to scientist studying the crater, and he replied that the idea was new to him. I subsequently found one site not written by a scientist mentioning the possibility of methane hydrate having been ignited. It seems to me that methane hydrate might also have produced a large amount of soot that could have blocked sunlight, contributing to long winter and extinctions Please comment.
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