Re: [meteorite-list] Largest Crater in the Sahara Desert and LDG -- ONE MORE ...
Hola Sterling, and thank you for the gracious email. Hopefully this gas cooled down; I won't go for another round on this one now, I promise. I pray the tektite debate won't continue until after we are dust, but in some places, probably you are dead right there. I've always thought that one of the great advantages of American education's system is the frequently criticized postal service and open communications in research, plus the Universities' quickness to pay for the postage of its faculty members without too many questions, and the researchers desire to share their work with other professionals and neophytes alike. I'm really sad you don't have the access level you'd like, it reminds me of our situation in Mexico - So far from God, but so near to the USA. Thankfully, ten-year old Meteoritics full text articles are usually available from the Harvard NASA Smithsonian ADS service, so at least you can see et. al. including Dr. Koeberl's original article there: http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992Metic..27R.298Tl ink_type=GIFdb_key=AST Oops wrong one. This particular article is a provocative one though for another thread, with much more application that it ever dreamed and a lively subject for discussion where some meteoritical forensics can actually weigh in on these disputes. So that you are properly armed and dangerous next time, here's the right link to Dr. Koeberl's article we discussed: http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1991Metic..26...41Md b_key=ASTlink_type=ARTICLE As far as Guy Heinen's book, your second hand source, all I can say is that it is a superb collection of information under one roof, but as you can see, despite all their efforts, the translation probably has some issues, and as you found out, the table and conclusions were not very clear. And the paper actually was more of a study of the Zhamanshin Crater, its source rock, and tektite-like Irghizites and then a suggested path to pursue bigger problems. Amazing, considering Dr. Koeberl helped edit the book, but I promised not to get into this, and the researchers are all good ones. At least I can take solace now in the fact that the cosmo- and geochemists weren't really in a conspiracy to get me*, it was just a very motivated amateur astronomer who teaches elementary school in his paid time. He sounds like he could be a very welcomed asset to out discussion group, though I don't know him personally!! I completely agree with you regarding the clues in Fluorine, whether alone or with Boron, so I can't really add anything to what you've already said there, other than clues being relatively common, but true conclusions and generalizations are so darned elusive. *Did I mention I am a lowly physical chemist? Lowly, because at least here in Mexico, we can't seem to get much respect from the geologists. It is really a sad situation but there is a distinct bias you could cut with a knife. And even the most prolific and one of the most distinguished Geologist of our State University's Geology Department is actually a Chemist like me, and he still get's a Rodney Dangerfield... Saludos and best wishes, Doug __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Largest Crater in the Sahara Desert and LDG
Hi, Mike, The hypervelocity impact has always been in the running for The Tektite Source, off and on. The worse case would be a comet with an orbital eccentricity of .99 in a retrograde orbit. In other words, a first-timer falling out of the Oort Cloud from 10,000 AU or 20,000 AU out that's traveling like the proverbial bat out of hell by the time it gets to the inner Solar System that would then smack into the Earth when we're headed right for it. All the bad luck in the world. A comet's still bound to the Sun's gravity, so we can figure its velocity at the Earth's orbital distance, sum up all the bad-luck velocities, and get a maximum possible impact velocity of about 73.4 km/sec. That for any object gravitationally bound to the Sun (not an alien spacecraft under power), but comets are the only likely ones. The average impact velocity we'd get from a NEA would be 15-20 km/sec, so the retrograde comet hit would be about four times faster. Back to the bad luck department: the energy depends on the square of the velocity, so the bad-luck comet hit would deliver sixteen times the energy per pound than the usual mass-extincting disaster. Ouch x 16. So, it's really nice that the odds of a collision with a long-period comet are so low... (To figure those odds, calculate the area of a sphere with a radius equal to the Earth's orbital distance, divide by the cross-sectional area of the Earth's disk, and you have the odds of any one long-period comet, which could come from any direction, hitting the Earth.) When all is said and done, the chances are from one hit per 2,000,000,000 years to one hit per 500,000,000 years, depending on how frequent long-period comets are (argument in progress). Really nice, because such a comet could just as easily be up to 100 miles across or more, or like the recent Hale-Bopp. (Was it only 40 or 60 miles across?) Getting hit by an object this size, at any speed, makes the Big Kill All The Dinosaurs Asteroid (10 miles across) look like a kid's fire- cracker, a puny firecracker at that. Getting hit by a 100 mile object is just plain unthinkable. Are there other big objects? Chiron, the Centaur (which is both Comet 95P and Minor Planet 2060) between Saturn and Uranus and is about 160 miles across, was deflected there by Jupiter (most likely). All the Centaur objects (all pretty big, over 100 of them!) are orbitally unstable on a 100,000 year time scale and have about a 20% chance of escaping inward (and 80% outward). Root for them to head outward, please. But comets in general have more eccentric orbits than asteroids, which means higher impact velocities in general, so their impacts are likely to be more energetic (by the square, a mere 44% increase resulting in double the punch). But even mildly big objects, 500 meters or 1000 meters, are not bothered by our atmosphere one bit, even at a 30 degree angle. Air provides great protection against small and medium bodies but once you get up to the large size impactor, it doesn't even slow it down. A 500 meter body that would achieve 15 km/sec might only lose less than 1 km/sec of that velocity, not a big help. A 1000 meter (and up) body would lose even less speed. A 10,000 meter body wouldn't slow down at all. There are other reasons for suspecting a comet- tektite connection, but I'm saving it for another post to the List. Stay tuned. Sterling K. Webb - - Original Message - From: Mike Fowler [EMAIL PROTECTED] To: meteorite-list@meteoritecentral.com Cc: Mike Fowler [EMAIL PROTECTED] Sent: Saturday, March 04, 2006 11:11 AM Subject: [meteorite-list] Largest Crater in the Sahara Desert and LDG This is actually a more general point: there are lots and lots of impact craters but very few tektite producing ones; why? Sterling K. Webb Why not very high velocity comet impacts, at a near vertical angle. Maximum cometary velocities would be about 10 times more than average asteroidal impacts. Near vertical would reduce the atmospheric column that the explosion has to punch thru to the minimum. Looked at from this point of view, perhaps only 1 in 100 crater producing impacts would qualify, which might explain why there are many large craters, but few tektite strewn fields. Mike Fowler Chicago __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Largest Crater in the Sahara Desert and LDG
Sterling W. writes: Doug, the actual language Kroeberl uses is that the F/B ratio of tektites should tend toward 1.0. This is Professional Science Speak for too complex to model exactly, but most of the cows ought to stampede in this direction... Hola Sterling, I asked you where you got the moldavite value for boron. You are now a primary source on the Internet saying that moldavites have this content and some tektite man at some place like lpi may believe you... It is very tedious to measure boron apparenty by spectrophotometric methods - it would be a fair question to ask you how you got it...Slap me, call me insulting, do I really deserve it because it sure sounded to me you might have invented the typical value of Boron=30 ppm in moldavites and pass it off as a typical number for moldavites because you got caught up in a roll fitting numbers to produce a 1.0 ratio you were trumpeting - when you had no such data. If I am wrong please forgive me enough to be on speaking terms, and if I am right, please come clean. Let me say I am much more comfortable with this last post you made than the prior last off-the-wall statements about tektite formation at 34,000 degree (you really did say this, I read all of your posting) plasma-formed tektites miraculously being heated in microseconds to the point where first fluorine is driven off to a theoretical identical level as boron, and then they diffuse out at identical rates ignoring petty chemical differences. We could start with considering that at the temperature you quoted being reached, neither water, nor silicon dioxide the base material of tektite glass would survive, so I think you are confusing tektites with theoretical particle physics over a few pitchers in the Athenaeum. I mean this in the nice way, and need to state it as it is the heart of my disagreement on the sloopy use of the data. I am really entertained by your posts generally - you are probably my favorite poster! But you have have mixed speculation with data here and taken liberties to mix them and present them labeled as fact. While Dr. Koeberl (please check the proper your spelling of your sources' surname) may have used the word tend as you state above, did it occur he just meant that the average of a few measurements was in a ballpark of 1? Let's not turn this incredibly simple issue into a greased pig with talk of cows stampeding and so forth. I don't need to sort it out with Dr. Koeberl as you suggested, I think his paper was self explanatory, well done though not one of his better ones, though it would have benefitted by someone proofreading better the English as to not give rise to such ambiguities in interpretation. Also, as I asked you to kindly clarify, and you did, the sample size as I asked you to clarify was tiny - I'm not gonna let you off the hook on that yet. And you're right; he didn't analyze that many samples. I wish he had more data. Well, let's do better here: the paper has five tektite samples for which both fluorine and boron were determined. He found one ivorite with a F/B ratio of 0.40 (means more boron than fluorine). Yes, he did. And you can't discount it. It was one of only five samples. Call it an outlier if you wish. But it totally nukes your wishful morphing-random walking diffusion plasmoid theory and imaginative mechanisms which you presented as fact. Most results were 0.8 to 1.2, which indeed is a 'tendency toward 1.0, if you think numbers have tendencies. I don't think the numbers have tendencies in the sense you used them to build an astounding physicist view. I think numbers are cold and cruel. Let's look at the tektite numbers in the paper excluding the Muong Nongs as the authors suggest: [F]/[B] ratios Thailandite 1 1.2 Thailandite 2 1.5 Bediasite 1 0.8 Ivory C. tek. 1 1.2 Ivory C. tek. 2 0.4 Tending to 1.0? Professional science speak huh? No, no, no and no. Sorry, but no. I'd go for Settle in the ball park of 1.0, provided no one uses Sterling's logic to shove Fluorine and Boron into one ball, and provided that no one saying and implying that these molecules or elements coordinate themselves to reach equal levels in time to loose their identies only to regain them again... Degreasing the pig, let's grab a hold of it and cut to the throat of the issue. You originally argued that LDG's were extremely hot like tektites pointing to this fluorine-boron thermometer and told us without references that the fluorine and boron values were 7 ppm each in LDGs, arguing that this made them comparable to heat for tektites, and that the low absolute ppm numbers (which were lowers than most tektites, btw). You said that geochemists were behind this, not friendly physicists, and that all of this is established protocol for geo- and cosmo-chemists. You pointed to your theories of formation of tektites and then said this whole thing was not hatched by you.
Re: [meteorite-list] Largest Crater in the Sahara Desert and LDG -- ONE MORE TIME!
and their tektites do not match well for all elements in ways hard to explain. Paradoxically, the target rocks DO produce impact glasses at the same time and place; there are many varieties of impact glasses at Ries, in addition to the famous tektites, same for other sites. The chemistry of these impactites do not match the tektites from the same location. Hmm. b) Tektites are all the same because they are formed entirely from one specific type of impactor (of which, for some reason, we have no other samples, and not at all from the local target rocks. End of story. Anyone want to shave this puppy, or is that greased pig, with Occam's Razor? Koeberl? Nah, let's just read his paper to get it in writing: The low F and B contents in LDG and Aouelloul impact glasses are most probably due to low contents in the precursor materials. Koeberl's most probably due sounds suspiciously like he didn't test the source rock, or look it up either. I translate most probably due as I guess. Doesn't sound like hard data to me. He doesn't say, Since Rock X has F/B vaues of xxx/yyy... or even The report of Messrs, A, B, and X give xxx ppm for... He doing the bread-and-butter thing, writing a paper; if you have data, you use it. But beyond that, arguing away some parts of the results as due to characteristics of the source rock ASSUMES that the source rocks are the source of tektites, but that's one of things we're trying to find out, isn't it? Well, isn't it? Oh, and BTW, lighten up, Doug. People will still be arguing about tektites long after we're both dust, you know. Sterling K. Webb - - Original Message - From: [EMAIL PROTECTED] To: [EMAIL PROTECTED]; [EMAIL PROTECTED] Cc: [EMAIL PROTECTED]; [EMAIL PROTECTED]; Meteorite-list@meteoritecentral.com Sent: Monday, March 06, 2006 2:47 PM Subject: Re: [meteorite-list] Largest Crater in the Sahara Desert and LDG Sterling W. writes: Doug, the actual language Kroeberl uses is that the F/B ratio of tektites should tend toward 1.0. This is Professional Science Speak for too complex to model exactly, but most of the cows ought to stampede in this direction... Hola Sterling, I asked you where you got the moldavite value for boron. You are now a primary source on the Internet saying that moldavites have this content and some tektite man at some place like lpi may believe you... It is very tedious to measure boron apparenty by spectrophotometric methods - it would be a fair question to ask you how you got it...Slap me, call me insulting, do I really deserve it because it sure sounded to me you might have invented the typical value of Boron=30 ppm in moldavites and pass it off as a typical number for moldavites because you got caught up in a roll fitting numbers to produce a 1.0 ratio you were trumpeting - when you had no such data. If I am wrong please forgive me enough to be on speaking terms, and if I am right, please come clean. Let me say I am much more comfortable with this last post you made than the prior last off-the-wall statements about tektite formation at 34,000 degree (you really did say this, I read all of your posting) plasma-formed tektites miraculously being heated in microseconds to the point where first fluorine is driven off to a theoretical identical level as boron, and then they diffuse out at identical rates ignoring petty chemical differences. We could start with considering that at the temperature you quoted being reached, neither water, nor silicon dioxide the base material of tektite glass would survive, so I think you are confusing tektites with theoretical particle physics over a few pitchers in the Athenaeum. I mean this in the nice way, and need to state it as it is the heart of my disagreement on the sloopy use of the data. I am really entertained by your posts generally - you are probably my favorite poster! But you have have mixed speculation with data here and taken liberties to mix them and present them labeled as fact. While Dr. Koeberl (please check the proper your spelling of your sources' surname) may have used the word tend as you state above, did it occur he just meant that the average of a few measurements was in a ballpark of 1? Let's not turn this incredibly simple issue into a greased pig with talk of cows stampeding and so forth. I don't need to sort it out with Dr. Koeberl as you suggested, I think his paper was self explanatory, well done though not one of his better ones, though it would have benefitted by someone proofreading better the English as to not give rise to such ambiguities in interpretation. Also, as I asked you to kindly clarify, and you did, the sample size as I asked you to clarify was tiny - I'm not gonna let you off the hook on that yet. And you're right; he didn't analyze that many samples. I wish he had more data. Well, let's do better here: the paper has five tektite samples for which both fluorine
Re: [meteorite-list] Largest Crater in the Sahara Desert and LDG
Sterling W. writes: I don't know the values for the Nubia Sandstone, but the range of sandstones is fluorine 180 to 450 ppm and boron about 10 to 85 ppm. The figures for LDG is fluorine 7 ppm and boron 7 ppm, so you see how the ratios shift as the content drops. As the temperature rises (microsecond by microsecond), the fluorine content drops much faster than the boron content. At some very high temperature (variable for each source rock), both fluorine and boron levels become the same, but at a higher level than in the final product. After that point, both are driven out of the melt plasma at the same rate, their petty chemical differences totally overwhelmed by the energy available. So, fluorine goes faster until that point is reached, after then, they drop together. Hola Sterling, Petty chemical differenceshm.overwhelmed at moment x when they behave identically (this is the cartoon and then a miracle happens and we get the desired solution)...I hope you can do better than this! This last paragraph has pegged my bogometer and the needle broke as I see physical laws being bent to accomodate your interesting and provolking speculations. It's either the most unfounded, unscientific argument and counterintuitive I've ever heard you seriously make - or - you speak about this thermometer as if you actually were there watching the impact and taking notes by the microsecond on how Boron and Fluorine behave under singular circumstances and states that are poorly defined to start with! I didn't dispute the use of [F]:[B] to compare different forms from the same source rock (a reasonable use of the thermometer), that is not what you are doing. I hope you can see how you are pulling numbers from out of the air which are all over the map and cooking pretty conclusions out of them. To answer my question, I'd back up and ask for the following modest data: 1. reference - Where you got moldavites bottoming out at [B]=30 ppm (for [F]=30 ppm, at least)? 2. Based on how many samples is your typical value [F]:[B] of Ivory Coast tektites and what was the low end for the ratio? Was it a lot less than 1? How would your physics' scheme explain a value below 0.5 for the ratiosince you have re-enforced the point I most object to by saying they magically reach the same concentration and then decrease equally... 3. Without the respective values of F,B in Nubian sandstone near the crater, my question isn't anywhere near answered:( !! You mentioned: It looks like LDG had a very hot forming event, so the high water content is a real puzzle. It's only a real problem puzzle in this context because you have read too much into and extrapolated much too far with the halogen thermometer concept. The water, rather than being a problem to explain, might be telling you that the F:B interpretation and extrapolations are all wet..., there is also a failure to consider different resident times for the measureables in the melt as yet another additional consideration. Not to mention of course the alternative or coincident possibility that LDG's have that content due to the low or surface altitude at which they formed... And this: ALL terrestrial rocks have a F/B ratio greater than 5.0 (often 20 or 30). but all impact glasses, even the weakest dirtiest just barely melted impact glasses have a F/B ratio less than 5.0 -- the result of a few thousand degrees of heating. ALL is a very encompasing term. Are you sure it wasn't mentioned principally regarding a total of two dozen tektite samples and three events for which the craters are known, weighted grossly in favor of Indochinites - rather than the whole wide world? Sure, 5 quite possibly is the minimum in unimpacted sediments worldwide but I'd need more than an arbitrary statement to believe it after reading the other assertations...are we still refering to Dr. Koerbel's work? Bedtime, I have a date with a comet in a couple of hours:), 'Night,Doug __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Largest Crater in the Sahara Desert and LDG
Gee, Doug, For once, I am not creating a crackers theory of my own. I am merely explaining how a certain geochemical test procedure works. Not being a geo- or a cosmo- chemist, I am taking the word of Matthies, D. and Kroeberl, C., Fluorine and Boron Geochemistry of Tektites, Impact Glasses, and Target Rocks, Meteoritics, 26 (1991), 41-45, both of whom AM geochemists. Also, see K. H. Wedepohl, Handbook of Geochemistry (1978). Blah, blah. Think about it. You gotta rock. Mixture of complicated crystals. Many elements. Huge heating event. Rock melts. Rock vaporizes. Molecules dissociate. Now it's a plasma, composed entirely of elements, too hot to form compounds. The volatile elements in this plasma escape from the plasma faster than the less volatile, which in turn escape faster than the refractory (who are stubborn and hang around). The plasma continues to heat. Volatiles go faster and faster. At a high enough temperature, the mean free path of atoms and their rate of escape is pretty much totally determined by the thermal energy of the plasma and the mass of the atom and the chemical characteristics of the substance matter not at all. It's physics now, not chemistry. Element 5 (mass 11) and element 9 (mass 19) are both moving like there was a 38,000 degree plasma on their tail (and there is). They now escape at a similar rate. Get the literature. Look at the pretty graphs that show how it works. There's some chemical reason why this happens about the time they're at the same concentration, but I forget it. It's chemistry. Me, when I look at things like equilibrium condensation diagrams or the reverse of same, my eyes start to glaze over... So I just take their word for it. But as a physical phenomenon, it fits my intuition. Look at the other light atoms. Not many of them hanging around either. Makes silly hand gestures, points to self. I no chemist. Physicist. Like big things (universe, stars, planets, rocks the size of countries). Like little things (quarks, leptons, cute little bosons, petite atoms). Don't like things inbetween. That's why God made chemists and botanists. Let them sort it out. They like that sort of thing for some reason... In 1962, when the number of elementary particles officially went over 200, Enrico Fermi, getting old and cranky, yelled, Look at this f***g zoo! If I wanted this mess, I'd have become a botanist! (He was right; how can you have more elementary particles making up elements than there are elements? Maybe it means that making elements is hard.) Crusty old physicists. Show me String Theory when you can put the whole thing on ONE PAGE. Otherwise, go back and work on it some more. Deep breath. The F/B ratios for ALL terrestrial rocks comes from Kroeberl and Company (all of this does). That's for the bulk compositional analyses of crustal rocks everywhere that geologists have made 100,000's of for the last century or so. Boring... Boron's just not as common as fluorine. The ratios run 10:1, 20:1, 30:1. Earth rock just isn't (in bulk) boronic. That crusty stuff in Death Valley doesn't count... If boron was common, would they have send Ronald Reagan and those 20 mules into Death Valley? (Old TV referrence.) If you think this is all hooey, complain to Kroeberl and Co. Also Wedepohl, who publishes thick books full of endless tables of bulk elemental compsitions. Lemme know what happens. Seriously, I am miffed. I don't think this stuff is whacky enough to be one of my whacky notions, and I'm insulted that anyone should think so... Obviously, I'm not being whacky enough. I'm quiting. It's late enough that I could go out and wave at that comet myself. Sterling K. Webb -- - Original Message - From: [EMAIL PROTECTED] To: [EMAIL PROTECTED]; [EMAIL PROTECTED]; [EMAIL PROTECTED]; Meteorite-list@meteoritecentral.com Sent: Sunday, March 05, 2006 2:34 AM Subject: Re: [meteorite-list] Largest Crater in the Sahara Desert and LDG Sterling W. writes: I don't know the values for the Nubia Sandstone, but the range of sandstones is fluorine 180 to 450 ppm and boron about 10 to 85 ppm. The figures for LDG is fluorine 7 ppm and boron 7 ppm, so you see how the ratios shift as the content drops. As the temperature rises (microsecond by microsecond), the fluorine content drops much faster than the boron content. At some very high temperature (variable for each source rock), both fluorine and boron levels become the same, but at a higher level than in the final product. After that point, both are driven out of the melt plasma at the same rate, their petty chemical differences totally overwhelmed by the energy available. So, fluorine goes faster until that point is reached, after then, they drop together. Hola Sterling, Petty chemical differenceshm.overwhelmed at moment x when they behave identically (this is the cartoon and then a miracle happens and we get the desired solution
Re: [meteorite-list] Largest Crater in the Sahara Desert and LDG
Sterling: Sounds good to me (though I study big rocks that you can see with a telescope). It sounds like it is time for me to start reading up on tektites too! As a novice, would you basically say that tektites come from volatilized material that has recondensed while an impactite derives from melted material that never got hot enough to vaporize. Obviously, you would have ranges of materials (hotter vapor or hotter and more devolatilized liquid). Larry PS Did you see the comet? Never been clear enough and no access to a telescope where I am. Quoting Sterling K. Webb [EMAIL PROTECTED]: Gee, Doug, For once, I am not creating a crackers theory of my own. I am merely explaining how a certain geochemical test procedure works. Not being a geo- or a cosmo- chemist, I am taking the word of Matthies, D. and Kroeberl, C., Fluorine and Boron Geochemistry of Tektites, Impact Glasses, and Target Rocks, Meteoritics, 26 (1991), 41-45, both of whom AM geochemists. Also, see K. H. Wedepohl, Handbook of Geochemistry (1978). Blah, blah. Think about it. You gotta rock. Mixture of complicated crystals. Many elements. Huge heating event. Rock melts. Rock vaporizes. Molecules dissociate. Now it's a plasma, composed entirely of elements, too hot to form compounds. The volatile elements in this plasma escape from the plasma faster than the less volatile, which in turn escape faster than the refractory (who are stubborn and hang around). The plasma continues to heat. Volatiles go faster and faster. At a high enough temperature, the mean free path of atoms and their rate of escape is pretty much totally determined by the thermal energy of the plasma and the mass of the atom and the chemical characteristics of the substance matter not at all. It's physics now, not chemistry. Element 5 (mass 11) and element 9 (mass 19) are both moving like there was a 38,000 degree plasma on their tail (and there is). They now escape at a similar rate. Get the literature. Look at the pretty graphs that show how it works. There's some chemical reason why this happens about the time they're at the same concentration, but I forget it. It's chemistry. Me, when I look at things like equilibrium condensation diagrams or the reverse of same, my eyes start to glaze over... So I just take their word for it. But as a physical phenomenon, it fits my intuition. Look at the other light atoms. Not many of them hanging around either. Makes silly hand gestures, points to self. I no chemist. Physicist. Like big things (universe, stars, planets, rocks the size of countries). Like little things (quarks, leptons, cute little bosons, petite atoms). Don't like things inbetween. That's why God made chemists and botanists. Let them sort it out. They like that sort of thing for some reason... In 1962, when the number of elementary particles officially went over 200, Enrico Fermi, getting old and cranky, yelled, Look at this f***g zoo! If I wanted this mess, I'd have become a botanist! (He was right; how can you have more elementary particles making up elements than there are elements? Maybe it means that making elements is hard.) Crusty old physicists. Show me String Theory when you can put the whole thing on ONE PAGE. Otherwise, go back and work on it some more. Deep breath. The F/B ratios for ALL terrestrial rocks comes from Kroeberl and Company (all of this does). That's for the bulk compositional analyses of crustal rocks everywhere that geologists have made 100,000's of for the last century or so. Boring... Boron's just not as common as fluorine. The ratios run 10:1, 20:1, 30:1. Earth rock just isn't (in bulk) boronic. That crusty stuff in Death Valley doesn't count... If boron was common, would they have send Ronald Reagan and those 20 mules into Death Valley? (Old TV referrence.) If you think this is all hooey, complain to Kroeberl and Co. Also Wedepohl, who publishes thick books full of endless tables of bulk elemental compsitions. Lemme know what happens. Seriously, I am miffed. I don't think this stuff is whacky enough to be one of my whacky notions, and I'm insulted that anyone should think so... Obviously, I'm not being whacky enough. I'm quiting. It's late enough that I could go out and wave at that comet myself. Sterling K. Webb -- __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list -- Dr. Larry A. Lebofsky Senior Research Scientist Co-editor, Meteorite __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Largest Crater in the Sahara Desert and LDG
the impact site, goes right out the window. The high speed re-entry of an immense swarm of glassy rubble (and when I say immense, I mean many billions of pieces) could produce a rain of glass vapor cooling to molten microspheres in the last moment before landing, and then another swarm, and another. Would that necessarily happen adjacent to the crater? No. There are ocean finds of layered tektites off the Caribbean coast of South America. That's a long way from the Chessy Crater. Of course, they could also be found closer to the crater, like in Georgia (they are), but they could be anywhere in the strewn field. That's the point. This just takes an already headache level, very complicated mystery and boosts it way up the Migraine Scale to what-is-going-on-here? It produces the paradoxical result that, while ordinary tektites may be superheated droplets of melt that didn't quite vaporize, the Muong Nongs may be the product of droplet condensation from a vapor, a conclusion that is pretty much completely backwards from the way most people conceptualize the formation of tektites. There's that headache factor again... Why do the layers tend to alternate colors? Shut up; I have a headache... As for Darryl's analysis of the micro-voids in Muong Nongs, I don't know if he ever published or even communicated it. We were talking about it the week he died. Somebody want to section a Muong Nong and look? By the way, there are layered tektites from three of the four major strewn fields, all but the Ivory Coast. (But, then, ivorites are very rare, with few examples compared to other falls.) So, it's probably a universal outcome of the Tektite Event, whatever that is. While I always worried about the asteroid hit, or the stray comet hit, the usual cosmic catastrophe, a straightforward impact event, I was so fascinated by tektites that I never thought to worry that much about the event. But after envisioning clouds of rock vapor and repeated fiery rains of molten droplets over hundreds of miles, I wonder if we ought to worry more than we do. Or at least, figure out what they are... Sterling K. Webb -- - Original Message - From: Norm Lehrman [EMAIL PROTECTED] To: Larry Lebofsky [EMAIL PROTECTED]; Sterling K. Webb [EMAIL PROTECTED] Cc: [EMAIL PROTECTED]; [EMAIL PROTECTED]; [EMAIL PROTECTED]; Meteorite-list@meteoritecentral.com Sent: Sunday, March 05, 2006 9:13 AM Subject: Re: [meteorite-list] Largest Crater in the Sahara Desert and LDG All, Thanks for the fabulous discussion. I had to take time out from the discourse to wash, size-sort, cull, and count 10,000 tektites for an order I'm supposed to ship tomorrow, and all of this gave me a lot to mull over. And it did a lot to reinvigorate the wonderment of the puzzle that first drew me to tektites. For any of you on the list that may be new to the subject, this discussion serves as an appetizer for the much larger array of puzzles posed by tektites. On the more immediate topics; Doug, I very much like your thought of an aerial thermal event like a mega-Tunguska for Muong Nongs and maybe Edieowie also. And Sterling, I to find the F/B story intuitively comfortable and rational. Larry, your comment regarding something like a plasma condensate for true tektites as opposed to simple splash glass impactites feels good. Pieces are beginning to fall into place in new combinations for me. More after I get the counting finished--- Norm http://tektitesource.com --- Larry Lebofsky [EMAIL PROTECTED] wrote: Sterling: Sounds good to me (though I study big rocks that you can see with a telescope). It sounds like it is time for me to start reading up on tektites too! As a novice, would you basically say that tektites come from volatilized material that has recondensed while an impactite derives from melted material that never got hot enough to vaporize. Obviously, you would have ranges of materials (hotter vapor or hotter and more devolatilized liquid). Larry PS Did you see the comet? Never been clear enough and no access to a telescope where I am. -- Dr. Larry A. Lebofsky Senior Research Scientist Co-editor, Meteorite __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Largest Crater in the Sahara Desert and LDG
like oceanic microtektites do. A rock (or big tektite) is a great piece of packaging to preserve the original composition within. A concretation of 50 micrometer particles is not. They fell (repeatedly) as tiny particles on dirt, water, plant life, big tropical bugs, perhaps the occasional hapless hominid, incorporating a lot of junk. Then, the tiny spheres of the more porous tektite started soaking up gases, water vapor, losing silica content, and so forth, a kind of weathering their more solid cousins are immune to. Oceanic microtetites decay this way and are believed to decay to clays eventually. Muong Nongs are layered, sub-layered, and sub-sub-layered, the result of many rains of fire over some short time scale. Fiery rain, fiery rain, fiery rain, and after that, fiery rain. So, again the simple impact scenario -- boom, melt, plop! -- fails. There's only one impact, hence there would be only one plop! In fact, with this composition, the one thing everybody seems certain of, that they are found near the impact site, goes right out the window. The high speed re-entry of an immense swarm of glassy rubble (and when I say immense, I mean many billions of pieces) could produce a rain of glass vapor cooling to molten microspheres in the last moment before landing, and then another swarm, and another. Would that necessarily happen adjacent to the crater? No. There are ocean finds of layered tektites off the Caribbean coast of South America. That's a long way from the Chessy Crater. Of course, they could also be found closer to the crater, like in Georgia (they are), but they could be anywhere in the strewn field. That's the point. This just takes an already headache level, very complicated mystery and boosts it way up the Migraine Scale to what-is-going-on-here? It produces the paradoxical result that, while ordinary tektites may be superheated droplets of melt that didn't quite vaporize, the Muong Nongs may be the product of droplet condensation from a vapor, a conclusion that is pretty much completely backwards from the way most people conceptualize the formation of tektites. There's that headache factor again... Why do the layers tend to alternate colors? Shut up; I have a headache... As for Darryl's analysis of the micro-voids in Muong Nongs, I don't know if he ever published or even communicated it. We were talking about it the week he died. Somebody want to section a Muong Nong and look? By the way, there are layered tektites from three of the four major strewn fields, all but the Ivory Coast. (But, then, ivorites are very rare, with few examples compared to other falls.) So, it's probably a universal outcome of the Tektite Event, whatever that is. While I always worried about the asteroid hit, or the stray comet hit, the usual cosmic catastrophe, a straightforward impact event, I was so fascinated by tektites that I never thought to worry that much about the event. But after envisioning clouds of rock vapor and repeated fiery rains of molten droplets over hundreds of miles, I wonder if we ought to worry more than we do. Or at least, figure out what they are... Sterling K. Webb -- - Original Message - From: Norm Lehrman [EMAIL PROTECTED] To: Larry Lebofsky [EMAIL PROTECTED]; Sterling K. Webb [EMAIL PROTECTED] Cc: [EMAIL PROTECTED]; [EMAIL PROTECTED]; [EMAIL PROTECTED]; Meteorite-list@meteoritecentral.com Sent: Sunday, March 05, 2006 9:13 AM Subject: Re: [meteorite-list] Largest Crater in the Sahara Desert and LDG All, Thanks for the fabulous discussion. I had to take time out from the discourse to wash, size-sort, cull, and count 10,000 tektites for an order I'm supposed to ship tomorrow, and all of this gave me a lot to mull over. And it did a lot to reinvigorate the wonderment of the puzzle that first drew me to tektites. For any of you on the list that may be new to the subject, this discussion serves as an appetizer for the much larger array of puzzles posed by tektites. On the more immediate topics; Doug, I very much like your thought of an aerial thermal event like a mega-Tunguska for Muong Nongs and maybe Edieowie also. And Sterling, I to find the F/B story intuitively comfortable and rational. Larry, your comment regarding something like a plasma condensate for true tektites as opposed to simple splash glass impactites feels good. Pieces are beginning to fall into place in new combinations for me. More after I get the counting finished--- Norm http://tektitesource.com --- Larry Lebofsky [EMAIL PROTECTED] wrote: Sterling: Sounds good to me (though I study big rocks that you can see with a telescope). It sounds like it is time for me to start reading up on tektites too! As a novice, would you basically say that tektites come from volatilized material that has recondensed while an impactite derives from melted material that never got hot enough to vaporize. Obviously, you would have ranges of materials
Re: [meteorite-list] Largest Crater in the Sahara Desert and LDG
- - Original Message - From: [EMAIL PROTECTED] To: [EMAIL PROTECTED]; [EMAIL PROTECTED]; Meteorite-list@meteoritecentral.com Sent: Friday, March 03, 2006 7:15 PM Subject: Re: [meteorite-list] Largest Crater in the Sahara Desert and LDG Hola Norm, so it seems we actually agree on most of the points, including the most important one: the subjectivity of the definition. You are just wanting to be more liberal...and me more stoodgy...I wasn't dodging the layered tektite issue when I said not to bring it up (which you unfortunately did:)). Clearly layered tektites are closer to impact glasses in the continuum and I was just trying to cleanly conceptualize. The definition of 'tektite' is a human classification which like most, depends on a clear understanding of a concept, not a recipe. The Muong Nong glasses (vs. tektites) as many experts also call them deserve a category by themselves so if you want to point to experts calling them tektites as support for calling the LDG's also tektites, all I can say is we are pushing the concept even further. You do mention the meteoritic content of Indochinites (=Australasian tektites). Yes a small component of iron has been detected, but this is very rare, and no where near the content in LDG which can approach a 0.5%. You didn't mention that the partial pressure of the air in the bubbles of the Indochinites corresponds to the upper atmosphere, and that in LDG I am assuming it corresponds to the surface. This shouldn't be a surprise as the water should not be linearly independent - thus they ought to track similarly. Good point on the desert weathering, but is there a real strewn field defined for LDG's, as we find with other conceptually true-to-form tektites (pun:))? If any evidence could be found, your argument would be more solid, as a of evidence isn't any proof of anything. Try checking nobel gas ratios and I bet the tektite concept will be even further away... Where I must really agree with you and put all grammatical gymnastics and opinions aside, is where you make the best point of the whole discussion, imho. That maybe our definition of tektites whatever that concept may be is based on faulty ideas. With liberty taken, that maybe it will change as we learn more. Yes, I buy that, I believe that is a distinct possibility. Things were so much simpler when we all agreed they were blasted from the Moon and the aerodynamic shapes and low water content actually meant something more to the experts of that time. Gor the time being, I be conservative on the definitions for the distinctions mentioned. Show me one aerodynamically shaped LDG besides one sculpted by a Neanderthal, and I'll recommend you for a Harvey award which would be quite fitting:), and definitely a nobel prize in the meteoritical community...for the moment we think there is a crater now, well, we already called them impact glasses, and now we have all these years of human transport mucking it up for these highly prized special glasses. Perhaps little Norm and little Doug in the 100th century will follow in our footsteps. Norm will say, Doug, look at all the chondrites in the USA, and there are none in the Sahara. Looks like the major strewn field is into North America and then a minor one into Europe. And Doug will say, I don't know, they weren't witnessed falls Jokes aside, the concepts are pretty clear --- high energy, less meteoritic content, water content too low for earth's surface under all available explanations, aerodynamic shapes, minimal nobel gas concentration typical of higher atmosphere, upper atmosphere pressures(=low)...where does LDG have a positive? A crater in the same environment///I'll sit this one out on the fence...but note it duly with curiosity and opportunity... Saludos, Doug Norm L. wrote: Doug, Good points all, but if you want to raise the water/purity issue, you can't dodge the Muong Nong issue. (The best answer is that they shouldn't be called tektites, BUT, they ARE so called by all authorities). With LDG, it can be reasonably argued that flight-related morphology has been erased by ventifaction. In the area where this stuff is found, it is literally reasonable that ALL of the material has seen the wind and its entrained sand. LDG is pretty fine, clean glass, albeit with a higher water content. (So, here again, people have dodged the issue by calling them Muong Nongs---) As for inclusion of impactor material in LDG, you've got to remember that iron spherules are found in Australasian tektites. Good chance that's impactor condensate. I truly have no argument with the water content criterion. That's probably the best definitional parameter we have. But it makes me a bit nervous to turn the whole matter over to such a narrow definition. Are we positive, given all that we don't know about tektites, that there can't be any wet ones? Should we now start calling Pyrex another variety
Re: [meteorite-list] Largest Crater in the Sahara Desert and LDG
Sterling W. writes: Crustal rocks have 5 or 10 times more fluorine than boron. Tektites should have a ratio of 1.0, indicating that they were heated to temperatures high enough to drive off most of the fluorine and leave the two halogens at identical levels (however low the absolute amount), and indeed tektites have values that float around 1.0 (like 0.8 to 1.2). The tested LDG F/B ratio is 1.0. Norm, Sterling, Mark, Tracy, list, I'm still on the fence about Libyan Desert Glass and how it fits into the puzzle and I wanted to thank Norm for the motivation to reconsider some of it based on the additional support that that LDG may have actually been tossed a significant (lateral?) distance to its resting point. Norm, my thoughts on the difference in the mechanism of formation here are basically along the lines pursued by Wasson, that Muong Nongs (and probably LDG's) result from a different conceptual and physical event: that while they may be clearly or partially impacted and have received a portion of their formation from that, that importantaly also: a major source of the energy that led to their formation was being broiled by an overhead explosion perhaps of a manyfold-Tunguska type, or by the same clould of incredible enery flux that formed some of the true-to-form tektites. This is why I am on the fence - because I feel more comfortable with that scenario to fall back upon. Just want to hold on to a concept, of what tektite means to me as Norm originally asked. While Norm argued to liberalize the definition to include LDG's, I'm playing the conservative interpretation here like Sterling is also joining to do. I don't disagree, just ask for one positive indication in my preferred set of rules. Norm might just be right if we play by his rules and accept that LDG's were chucked a good distance and thus call them tektites based on that criterion. At minimumn LDGs are more important now as we glean more information from them and maybe an additional piece of the endless puzzle. I am really not quite sure why Sterling mentions the F and B assays would tend to identical levels in tektites, and I while it may be my turn to split hairs, I think this is an interesting research point, but presented inside out. Yes, Fluorine is generally more volatile and probably preferentially driven off, though we should verify this is true for the source matrix solubility before being 100% convinced. The major problem I have here is that there is nothing magic about having them with the same concentration level as you imply, I think this is just a coincidence on what has been looked at so far, possibly related to the temperatures and residence times (determined by physical constraints) in the liquid state of formation too, yes, of course, but that is as far as I would go. That is why I think it is too great a leap of faith to discuss why they would be perfect tektites based on these measurements. Putting this [F]:[B] further under the microscope, it is also of academic interest to compare this to the source rock - but I would never flip that around to discuss why [F] and [B] should be identical or at a particular ratio without knowing the initial values in the source rock, since I cannot fathom any mechanism that would insist that tektites should have these levels identical, and the range you quote and attribute some special meaning to, anyway for tektites floating goes below 1.0 anyway, and as a matter of fact the tektites could easily have much lower values for this ratio than you quote, has Dr. Koerbel and colleagues ever fired up their special Boron sensitive electrode to check these numbers for moldavites lately? Basically, Sterling is making a big assumption by saying that the source rocks of the sandstone are in the range of 5 - 10 for a [F]:[B] ratio, and I think frankly that is a poke in the dark or leap of faith at minimum. I would much rather see someone actually go measure the [F] and [B] numbers for relatively unaltered sandstone near the excitingly discussed crater just to check that the ratios didn't happen to start out at values much closer to equal ... there is significant variation on the earth. The bottom line in my view is that the interpretation of the Fluorine and Boron concentration numbers and ratios is meaningful for an apples to apples comparison when the situation of the crater is not known if and only if we had tektites (or some other glass type) formed from the LDG event then we could measure (at least Dr. Koerbel and his colleagues could) and compare the tendencies with the series (e.g.,LDG, hypothetical button, hypothetical splashform,etc.) which I consider the more appropriate interpretation of this. Not take it out of context and generalize for the whole planet and say they should be perfect tektites. So there are not enough numbers put on this pig, in my opinion, and wish my disagreement on that split
Re: [meteorite-list] Largest Crater in the Sahara Desert and LDG
all. I wonder what they thought when the sky dropped millions of pieces of hot glass on them, to fall with a sizzle into the still water below? First, everything floods and we have to move up into these stinking FEMA treehouses, and now there's hot glass falling from the sky... The world is going to hell. Doug, did I answer your question? Sterling K. Webb - - Original Message - From: [EMAIL PROTECTED] To: [EMAIL PROTECTED]; [EMAIL PROTECTED]; [EMAIL PROTECTED]; Meteorite-list@meteoritecentral.com Sent: Saturday, March 04, 2006 4:05 PM Subject: Re: [meteorite-list] Largest Crater in the Sahara Desert and LDG Sterling W. writes: Crustal rocks have 5 or 10 times more fluorine than boron. Tektites should have a ratio of 1.0, indicating that they were heated to temperatures high enough to drive off most of the fluorine and leave the two halogens at identical levels (however low the absolute amount), and indeed tektites have values that float around 1.0 (like 0.8 to 1.2). The tested LDG F/B ratio is 1.0. Norm, Sterling, Mark, Tracy, list, I'm still on the fence about Libyan Desert Glass and how it fits into the puzzle and I wanted to thank Norm for the motivation to reconsider some of it based on the additional support that that LDG may have actually been tossed a significant (lateral?) distance to its resting point. Norm, my thoughts on the difference in the mechanism of formation here are basically along the lines pursued by Wasson, that Muong Nongs (and probably LDG's) result from a different conceptual and physical event: that while they may be clearly or partially impacted and have received a portion of their formation from that, that importantaly also: a major source of the energy that led to their formation was being broiled by an overhead explosion perhaps of a manyfold-Tunguska type, or by the same clould of incredible enery flux that formed some of the true-to-form tektites. This is why I am on the fence - because I feel more comfortable with that scenario to fall back upon. Just want to hold on to a concept, of what tektite means to me as Norm originally asked. While Norm argued to liberalize the definition to include LDG's, I'm playing the conservative interpretation here like Sterling is also joining to do. I don't disagree, just ask for one positive indication in my preferred set of rules. Norm might just be right if we play by his rules and accept that LDG's were chucked a good distance and thus call them tektites based on that criterion. At minimumn LDGs are more important now as we glean more information from them and maybe an additional piece of the endless puzzle. I am really not quite sure why Sterling mentions the F and B assays would tend to identical levels in tektites, and I while it may be my turn to split hairs, I think this is an interesting research point, but presented inside out. Yes, Fluorine is generally more volatile and probably preferentially driven off, though we should verify this is true for the source matrix solubility before being 100% convinced. The major problem I have here is that there is nothing magic about having them with the same concentration level as you imply, I think this is just a coincidence on what has been looked at so far, possibly related to the temperatures and residence times (determined by physical constraints) in the liquid state of formation too, yes, of course, but that is as far as I would go. That is why I think it is too great a leap of faith to discuss why they would be perfect tektites based on these measurements. Putting this [F]:[B] further under the microscope, it is also of academic interest to compare this to the source rock - but I would never flip that around to discuss why [F] and [B] should be identical or at a particular ratio without knowing the initial values in the source rock, since I cannot fathom any mechanism that would insist that tektites should have these levels identical, and the range you quote and attribute some special meaning to, anyway for tektites floating goes below 1.0 anyway, and as a matter of fact the tektites could easily have much lower values for this ratio than you quote, has Dr. Koerbel and colleagues ever fired up their special Boron sensitive electrode to check these numbers for moldavites lately? Basically, Sterling is making a big assumption by saying that the source rocks of the sandstone are in the range of 5 - 10 for a [F]:[B] ratio, and I think frankly that is a poke in the dark or leap of faith at minimum. I would much rather see someone actually go measure the [F] and [B] numbers for relatively unaltered sandstone near the excitingly discussed crater just to check that the ratios didn't happen to start out at values much closer to equal ... there is significant variation on the earth. The bottom line in my view is that the interpretation of the Fluorine and Boron
Re: [meteorite-list] Largest Crater in the Sahara Desert and LDG
Bernd list, This is indeed exciting, and may finally justify LDG being recognized as a true tektite rather than a simple impactite. Although the article doesn't give us much for location beyond at the northern tip of the Gilf Kebir region, that's close enough, as the LDG strewn field is immediately north of the Gilf Kebir. The 28.5 ma date for LDG should be a good number (fission track). The 100 million year sandstone mentioned as the crater target rock is perfect. For years it has been argued that the Nubia group sandstones are the geochemically perfect precursor for LDG. Interestingly, this raised a problem for researchers looking for a local LDG source crater as there are good geological arguments that the Nubia sandstones were covered by younger formations in the LDG strewn field at 28.5 ma and would not have been available as target rocks. With the revelation that this newly recognized crater did indeed impact the sandstones, we're almost there. Now, all we have to do is eject the LDG a hundred km or so northwards and the picture works fine. (The long axis of the strewn field is roughly N-S). Where is the dividing line between impactite and tektite? I'd like to hear what others may understand, but my impression is that it fundamentally hinges on distance the glassy material is ejected from the crater. Material found only in and immediately around the source crater is impactite. Stuff blasted tens to hundreds of km or more crosses the definitional boundary into tektites. If this is the criterion, LDG was already home free in my book insofar as the known strewn field has a long axis of at least 150 km, so even if there was a now-erosionally removed crater at one end of the strewn field proper, some of the glass would've already required over 100 km ejection distance. Now, I'm guessing we may be talking a couple hundred km, maybe more. Is that sufficiently far to legitimize LDG as a true tektite? (From Ries-Norlingen to the Czech moldavite fields is about 300 km). Cheers, Norm http://tektitesource.com --- [EMAIL PROTECTED] wrote: Hi Ron and List, Like so many others, I was eagerly flying over the lines in search of a hint to LDG (Libyan Desert Glass),and, there it is (of course ;-): since its shape points to an origin of extraterrestrial impact, it will likely prove to be the event responsible for the extensive field of 'Desert Glass'-yellow-green silica glass fragments found on the desert surface between the giant dunes of the Great Sand Sea in southwestern Egypt. But: may have been formed by a meteorite impact tens of millions of years ago. How many *tens* of millions of years ago ??? If current age estimates are correct, LDG has an age of ~28 Ma. Any thoughts out there, ... Norm? Cheers, Bernd __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Largest Crater in the Sahara Desert and LDG
Norm L. writes: Where is the dividing line between impactite and tektite? I'd like to hear what others may understand, but my impression is that it fundamentally hinges on distance the glassy material is ejected from the crater. Material found only in and immediately around the source crater is impactite. Stuff blasted tens to hundreds of km or more crosses the definitional boundary into tektites. If this is the criterion, LDG was already home free Hola Norm, yet again here's another one of those awkward definitions that when overyly analyzed starts falling apart. I think the distance criterion is not THE criterion, but rather a tektite differs from an impact glass in that the tektite has actually been exposed to general conditions of enough kinetic and thermal energy to create a greater melt uniformity where the original impactor has transmitted that energy cleanly, and in such a great quantity that the energy is also enough to propel tektites into the upper atmosphere and have them re-enter ablating like meteorites. These are a bunch of hand-waving concepts, but as we know, it seems the one factor that really distinguishes tektites is the low water content. LDG's have at least 5 times the typical water content of the cleaner tektites, and they contain inclusions including those of the impactor, and aerodynamic shapes are not really known I believe. In fact the water content of LDG's at the low end of 5 times the amount of the cleaner tektites actually goes practically as high as obsidian. They don't usually look very aerodynamic and they have meteorites inside them. They deserve some distinction, they are dirty glass. Now all of this about water content might be just an academic distinction, except for one exception. One of the greatest mysteries of tektites is derived from the mystery of exactly what physical laws were twisted to get that low water content and this more than anything else is the criterion as much as the mystery. Plus they are generally clean (OK, they have smalled fused cuartz. etc., but there there tends to be a bimodal distribution between clean tektites and impact glasses as far as inclusions = so far you have clean ones and dirty ones) Please don't bring up layered tektites I don't want the definition system to fail even more... But practically speaking, you would have to be right that there is a continuum, just like in the definition of a planet, etc., the world tends towards complexity just when you get it all figured out...and soon we will come to know of the impektite that bridges tektites, water and all, with LDGs and other impact glasses. Better yet how about just saying they are all impact glasses - which they are no matter who starts talking about flying - and that tektites just had a higher energy/diffusion/flux melt event which is witnessed in the record by water content...If cats could only talk they could tell us how long we have erred on visible light as they see into the near UV, don't they? What's the use of going at it with a cat over the definition of visible light?:) My 2 centavos...Doug __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Largest Crater in the Sahara Desert and LDG
Doug, Good points all, but if you want to raise the water/purity issue, you can't dodge the Muong Nong issue. (The best answer is that they shouldn't be called tektites, BUT, they ARE so called by all authorities). With LDG, it can be reasonably argued that flight-related morphology has been erased by ventifaction. In the area where this stuff is found, it is literally reasonable that ALL of the material has seen the wind and its entrained sand. LDG is pretty fine, clean glass, albeit with a higher water content. (So, here again, people have dodged the issue by calling them Muong Nongs---) As for inclusion of impactor material in LDG, you've got to remember that iron spherules are found in Australasian tektites. Good chance that's impactor condensate. I truly have no argument with the water content criterion. That's probably the best definitional parameter we have. But it makes me a bit nervous to turn the whole matter over to such a narrow definition. Are we positive, given all that we don't know about tektites, that there can't be any wet ones? Should we now start calling Pyrex another variety of tektite? Clearly, we are including some process-related factors (even if just inferred) in our definition. It is very much like the planet issue. I keep thinking that there have been a lot of grade-school kids that got marked down on tests for answering the question: How many planets are in our solar system? wrong according to the erroneous wisdom of a given time. How many tektite-producing impacts have there been? I get weary of qualifying my answers with, Well, depending on whether or not you count LDG Cheers, Norm http://tektitesource.com --- [EMAIL PROTECTED] wrote: Norm L. writes: Where is the dividing line between impactite and tektite? I'd like to hear what others may understand, but my impression is that it fundamentally hinges on distance the glassy material is ejected from the crater. Material found only in and immediately around the source crater is impactite. Stuff blasted tens to hundreds of km or more crosses the definitional boundary into tektites. If this is the criterion, LDG was already home free Hola Norm, yet again here's another one of those awkward definitions that when overyly analyzed starts falling apart. I think the distance criterion is not THE criterion, but rather a tektite differs from an impact glass in that the tektite has actually been exposed to general conditions of enough kinetic and thermal energy to create a greater melt uniformity where the original impactor has transmitted that energy cleanly, and in such a great quantity that the energy is also enough to propel tektites into the upper atmosphere and have them re-enter ablating like meteorites. These are a bunch of hand-waving concepts, but as we know, it seems the one factor that really distinguishes tektites is the low water content. LDG's have at least 5 times the typical water content of the cleaner tektites, and they contain inclusions including those of the impactor, and aerodynamic shapes are not really known I believe. In fact the water content of LDG's at the low end of 5 times the amount of the cleaner tektites actually goes practically as high as obsidian. They don't usually look very aerodynamic and they have meteorites inside them. They deserve some distinction, they are dirty glass. Now all of this about water content might be just an academic distinction, except for one exception. One of the greatest mysteries of tektites is derived from the mystery of exactly what physical laws were twisted to get that low water content and this more than anything else is the criterion as much as the mystery. Plus they are generally clean (OK, they have smalled fused cuartz. etc., but there there tends to be a bimodal distribution between clean tektites and impact glasses as far as inclusions = so far you have clean ones and dirty ones) Please don't bring up layered tektites I don't want the definition system to fail even more... But practically speaking, you would have to be right that there is a continuum, just like in the definition of a planet, etc., the world tends towards complexity just when you get it all figured out...and soon we will come to know of the impektite that bridges tektites, water and all, with LDGs and other impact glasses. Better yet how about just saying they are all impact glasses - which they are no matter who starts talking about flying - and that tektites just had a higher energy/diffusion/flux melt event which is witnessed in the record by water content...If cats could only talk they could tell us how long we have erred on visible light as they see into the near UV, don't they? What's the use of going at it with a cat over the definition of visible light?:) My 2 centavos...Doug
Re: [meteorite-list] Largest Crater in the Sahara Desert and LDG
Hola Norm, so it seems we actually agree on most of the points, including the most important one: the subjectivity of the definition. You are just wanting to be more liberal...and me more stoodgy...I wasn't dodging the layered tektite issue when I said not to bring it up (which you unfortunately did:)). Clearly layered tektites are closer to impact glasses in the continuum and I was just trying to cleanly conceptualize. The definition of 'tektite' is a human classification which like most, depends on a clear understanding of a concept, not a recipe. The Muong Nong glasses (vs. tektites) as many experts also call them deserve a category by themselves so if you want to point to experts calling them tektites as support for calling the LDG's also tektites, all I can say is we are pushing the concept even further. You do mention the meteoritic content of Indochinites (=Australasian tektites). Yes a small component of iron has been detected, but this is very rare, and no where near the content in LDG which can approach a 0.5%. You didn't mention that the partial pressure of the air in the bubbles of the Indochinites corresponds to the upper atmosphere, and that in LDG I am assuming it corresponds to the surface. This shouldn't be a surprise as the water should not be linearly independent - thus they ought to track similarly. Good point on the desert weathering, but is there a real strewn field defined for LDG's, as we find with other conceptually true-to-form tektites (pun:))? If any evidence could be found, your argument would be more solid, as a of evidence isn't any proof of anything. Try checking nobel gas ratios and I bet the tektite concept will be even further away... Where I must really agree with you and put all grammatical gymnastics and opinions aside, is where you make the best point of the whole discussion, imho. That maybe our definition of tektites whatever that concept may be is based on faulty ideas. With liberty taken, that maybe it will change as we learn more. Yes, I buy that, I believe that is a distinct possibility. Things were so much simpler when we all agreed they were blasted from the Moon and the aerodynamic shapes and low water content actually meant something more to the experts of that time. Gor the time being, I be conservative on the definitions for the distinctions mentioned. Show me one aerodynamically shaped LDG besides one sculpted by a Neanderthal, and I'll recommend you for a Harvey award which would be quite fitting:), and definitely a nobel prize in the meteoritical community...for the moment we think there is a crater now, well, we already called them impact glasses, and now we have all these years of human transport mucking it up for these highly prized special glasses. Perhaps little Norm and little Doug in the 100th century will follow in our footsteps. Norm will say, Doug, look at all the chondrites in the USA, and there are none in the Sahara. Looks like the major strewn field is into North America and then a minor one into Europe. And Doug will say, I don't know, they weren't witnessed falls Jokes aside, the concepts are pretty clear --- high energy, less meteoritic content, water content too low for earth's surface under all available explanations, aerodynamic shapes, minimal nobel gas concentration typical of higher atmosphere, upper atmosphere pressures(=low)...where does LDG have a positive? A crater in the same environment///I'll sit this one out on the fence...but note it duly with curiosity and opportunity... Saludos, Doug Norm L. wrote: Doug, Good points all, but if you want to raise the water/purity issue, you can't dodge the Muong Nong issue. (The best answer is that they shouldn't be called tektites, BUT, they ARE so called by all authorities). With LDG, it can be reasonably argued that flight-related morphology has been erased by ventifaction. In the area where this stuff is found, it is literally reasonable that ALL of the material has seen the wind and its entrained sand. LDG is pretty fine, clean glass, albeit with a higher water content. (So, here again, people have dodged the issue by calling them Muong Nongs---) As for inclusion of impactor material in LDG, you've got to remember that iron spherules are found in Australasian tektites. Good chance that's impactor condensate. I truly have no argument with the water content criterion. That's probably the best definitional parameter we have. But it makes me a bit nervous to turn the whole matter over to such a narrow definition. Are we positive, given all that we don't know about tektites, that there can't be any wet ones? Should we now start calling Pyrex another variety of tektite? Clearly, we are including some process-related factors (even if just inferred) in our definition. It is very much like the planet issue. I keep thinking that there have been a lot of
Re: [meteorite-list] Largest Crater in the Sahara Desert and LDG
Doug, I do enjoy your contributions. Always stimulating. I have no fundamental disagreements. Just a few hair-splitting points. Re: the partial pressures in Australasian bubbles. It has been argued that our numbers are bogus. As atmospheric water is absorbed into the hydrating tektite selvage lining a bubble, internal pressures can be considerably reduced, giving the false appearance of high altitudes. I have never seen anything about partial pressures in LDG glass. I'm not sure anything has ever been found sufficiently large to measure. Lacking such data, this argument is conceptual, not real. However it is a great research suggestion. With modern micro-techniques LDG bubbles should be revisited! As for a real strewnfield defined for LDGs as we find with other conceptually true to form tektites, yes, the finding area is quite sharply delimited at about 150 km X 50 km. If anything, the LDG area is atypically WELL defined relative to other tektites (I don't know much about Ivory Coast distribution. It may be comparable or smaller). I must admit, I have never seen anything even remotely resembling an erosionally-modified aerodynamically- shaped Libyan Desert Glass form. If you started with the typical morphologies of Australasians and sand-blasted them within an inch of their existence, we would still recognize some traces of original morphology. I must decline any hope of the Harvey Award on this matter. You are totally correct. LDG shows absolutely no hint of aerodynamic ablation modification. Deep enough, Norm http://tektitesource.com (a great place to view a huge selection of prime Libyan Desert Glass!) --- [EMAIL PROTECTED] wrote: Hola Norm, so it seems we actually agree on most of the points, including the most important one: the subjectivity of the definition. You are just wanting to be more liberal...and me more stoodgy...I wasn't dodging the layered tektite issue when I said not to bring it up (which you unfortunately did:)). Clearly layered tektites are closer to impact glasses in the continuum and I was just trying to cleanly conceptualize. The definition of 'tektite' is a human classification which like most, depends on a clear understanding of a concept, not a recipe. The Muong Nong glasses (vs. tektites) as many experts also call them deserve a category by themselves so if you want to point to experts calling them tektites as support for calling the LDG's also tektites, all I can say is we are pushing the concept even further. You do mention the meteoritic content of Indochinites (=Australasian tektites). Yes a small component of iron has been detected, but this is very rare, and no where near the content in LDG which can approach a 0.5%. You didn't mention that the partial pressure of the air in the bubbles of the Indochinites corresponds to the upper atmosphere, and that in LDG I am assuming it corresponds to the surface. This shouldn't be a surprise as the water should not be linearly independent - thus they ought to track similarly. Good point on the desert weathering, but is there a real strewn field defined for LDG's, as we find with other conceptually true-to-form tektites (pun:))? If any evidence could be found, your argument would be more solid, as a of evidence isn't any proof of anything. Try checking nobel gas ratios and I bet the tektite concept will be even further away... Where I must really agree with you and put all grammatical gymnastics and opinions aside, is where you make the best point of the whole discussion, imho. That maybe our definition of tektites whatever that concept may be is based on faulty ideas. With liberty taken, that maybe it will change as we learn more. Yes, I buy that, I believe that is a distinct possibility. Things were so much simpler when we all agreed they were blasted from the Moon and the aerodynamic shapes and low water content actually meant something more to the experts of that time. Gor the time being, I be conservative on the definitions for the distinctions mentioned. Show me one aerodynamically shaped LDG besides one sculpted by a Neanderthal, and I'll recommend you for a Harvey award which would be quite fitting:), and definitely a nobel prize in the meteoritical community...for the moment we think there is a crater now, well, we already called them impact glasses, and now we have all these years of human transport mucking it up for these highly prized special glasses. Perhaps little Norm and little Doug in the 100th century will follow in our footsteps. Norm will say, Doug, look at all the chondrites in the USA, and there are none in the Sahara. Looks like the major strewn field is into North America and then a minor one into Europe. And Doug will say, I don't know, they weren't witnessed falls Jokes aside, the concepts are pretty clear --- high energy, less
Re: [meteorite-list] Largest Crater in the Sahara Desert and LDG
Maybe they're just kryptonite! Occam's razor. Think about it. ;] http://theages.superman.ws/Encyclopaedia/kryptonite.php While I only have one small sample in my collection, reading the bantering about tektites on this List is always an interesting education for a rookie! Cheers, Pete From: Norm Lehrman [EMAIL PROTECTED] To: [EMAIL PROTECTED], [EMAIL PROTECTED],Meteorite-list@meteoritecentral.com Subject: Re: [meteorite-list] Largest Crater in the Sahara Desert and LDG Date: Fri, 3 Mar 2006 18:23:29 -0800 (PST) Doug, I do enjoy your contributions. Always stimulating. I have no fundamental disagreements. Just a few hair-splitting points. Re: the partial pressures in Australasian bubbles. It has been argued that our numbers are bogus. As atmospheric water is absorbed into the hydrating tektite selvage lining a bubble, internal pressures can be considerably reduced, giving the false appearance of high altitudes. I have never seen anything about partial pressures in LDG glass. I'm not sure anything has ever been found sufficiently large to measure. Lacking such data, this argument is conceptual, not real. However it is a great research suggestion. With modern micro-techniques LDG bubbles should be revisited! As for a real strewnfield defined for LDGs as we find with other conceptually true to form tektites, yes, the finding area is quite sharply delimited at about 150 km X 50 km. If anything, the LDG area is atypically WELL defined relative to other tektites (I don't know much about Ivory Coast distribution. It may be comparable or smaller). I must admit, I have never seen anything even remotely resembling an erosionally-modified aerodynamically- shaped Libyan Desert Glass form. If you started with the typical morphologies of Australasians and sand-blasted them within an inch of their existence, we would still recognize some traces of original morphology. I must decline any hope of the Harvey Award on this matter. You are totally correct. LDG shows absolutely no hint of aerodynamic ablation modification. Deep enough, Norm http://tektitesource.com (a great place to view a huge selection of prime Libyan Desert Glass!) --- [EMAIL PROTECTED] wrote: Hola Norm, so it seems we actually agree on most of the points, including the most important one: the subjectivity of the definition. You are just wanting to be more liberal...and me more stoodgy...I wasn't dodging the layered tektite issue when I said not to bring it up (which you unfortunately did:)). Clearly layered tektites are closer to impact glasses in the continuum and I was just trying to cleanly conceptualize. The definition of 'tektite' is a human classification which like most, depends on a clear understanding of a concept, not a recipe. The Muong Nong glasses (vs. tektites) as many experts also call them deserve a category by themselves so if you want to point to experts calling them tektites as support for calling the LDG's also tektites, all I can say is we are pushing the concept even further. You do mention the meteoritic content of Indochinites (=Australasian tektites). Yes a small component of iron has been detected, but this is very rare, and no where near the content in LDG which can approach a 0.5%. You didn't mention that the partial pressure of the air in the bubbles of the Indochinites corresponds to the upper atmosphere, and that in LDG I am assuming it corresponds to the surface. This shouldn't be a surprise as the water should not be linearly independent - thus they ought to track similarly. Good point on the desert weathering, but is there a real strewn field defined for LDG's, as we find with other conceptually true-to-form tektites (pun:))? If any evidence could be found, your argument would be more solid, as a of evidence isn't any proof of anything. Try checking nobel gas ratios and I bet the tektite concept will be even further away... Where I must really agree with you and put all grammatical gymnastics and opinions aside, is where you make the best point of the whole discussion, imho. That maybe our definition of tektites whatever that concept may be is based on faulty ideas. With liberty taken, that maybe it will change as we learn more. Yes, I buy that, I believe that is a distinct possibility. Things were so much simpler when we all agreed they were blasted from the Moon and the aerodynamic shapes and low water content actually meant something more to the experts of that time. Gor the time being, I be conservative on the definitions for the distinctions mentioned. Show me one aerodynamically shaped LDG besides one sculpted by a Neanderthal, and I'll recommend you for a Harvey award which would be quite fitting:), and definitely a nobel prize in the meteoritical community...for the moment we think there is a crater now, well, we already called them impact glasses, and now we have all these years of human
Re: [meteorite-list] Largest Crater in the Sahara Desert and LDG
Perhaps, rather than falling like a dead rat into the division between tektites and impactites, LDG is an indicator of more of a continuous spectrum. We already admit that there are anomalies where Muong Nong tektites and some aspects of australites don't fit comfortably within tektite parameters. The meteorite community acknowledges that almost every meteorite classification has its odd ducks that show characteristics more appropriate to other groups, or fit no existing group (that's how we get new classifications!) Could there conceivably be in between stages, where the irregularities of things like LDG actually indicate a median? Neither fish nor fowl, Tracy Latimer Hola Norm, so it seems we actually agree on most of the points, including the most important one: the subjectivity of the definition. __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
