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Re: Hell Creek (long)

I regret even making comments about this issue in the first place....... I seriously HATE doing this type of thing..........

In a message dated 5/30/2002 11:34:56 AM Eastern Daylight Time, graydon@dsl.ca writes:

Except that you're citing an order of magnitude smaller impactor
diameter which is _three_ orders of magnitude less mass and which
renders the simulation pretty much useless as an indicator for the
Chixuculb impact's behavour.

Fireball geometry doesn't scale linearily with size, but there are very
some significant scale points, especially the 'fireball diameter larger
than the tropopause height' and the 'fireball diameter larger than the
atmosphere height' ones.

In a message dated 5/30/2002 10:30:35 AM Eastern Daylight Time, jrccea@bellsouth.net writes:

Pretty small compared to Chicxulub, which would likely have been measured in teratons.

When exactly did I say I was comparing these to Chicxulub?????? Since "ocean impact" was mentioned, I thought I was just making remarks about experiments done to see the effects of 2 types of smaller impactors impacting the ocean from different trajectories.......  I mean.... I don't see Chicxulub mentioned in that paragraph at all...... I could be somehow blind to the word "Chicxulub" in that paragraph I suppose..... Some type of mental quirk maybe????.....  Try as I might, I just don't see Chicxulub in that paragraph.... Oh well..........

In a message dated 5/30/2002 10:30:35 AM Eastern Daylight Time, jrccea@bellsouth.net writes:

I'll pass too, for the same reason -- though I don't really see it as a nightmare, just a waste of my personal time.

Ummm..... Nope... I'm not beneath your foot......  It's not that the math is the nightmare for me my friend...... I was referring to the work involved and the moron of a professor that made that class a living hell and the hours and hours I spent on those papers...... All things that I definitely didn't want to remember, i.e: "The nightmare is coming back".

I made them because it seemed to me that you appeared to have been arguing both sides of the coin on several issues

Well..... I wasn't..... As I said, I guess I needed to clarify when I was talking oh so generally about impacting bodies..... I didn't think that type of ABC's was really necessary since you obviously know what you were talking about...... I'll make sure I spell every single thing out the next time I go about posting something  :-)

Well, Graydon agreed with my initial position.  Initially, you didn't.  Glad to see you've changed your mind.


Yes, and his response was contrary to your initial statement that crater shape is dependent upon impact angle no matter what the size (mass....kinetic energy) of the impactor.  My original point (as his) was that craters become more circular with increasing impact energy, so that effects of approach angle become subordinate with increasing energy.

Well...... if you post the rest of what I said......... "This doesn't make sense if you throw a rock in mud.

Chicxulub wasn't directly comparable to tossing a rock in mud.  I think we've beaten this particular horse into the ground.  I've found it enlightening though.All the best, Jim

Jim,.... not that I'm a last word freak or anything....... But...... once again....... coming from a direct observation that your tetraton blast at Chicxulub made a horseshoe-like crater.... and experiments (all be it on a tiny scale) replicated the very same effect if the impactor originated from a shallow, oblique angle, ....... and observations from other planetary bodies that demonstrate that this type of impact phenomenon does indeed happen, though it is extremely rare,.... and with Graydon explaining for the most part why it is so rare..... and with you saying that you agree with Graydon and have been thinking from the beginning the very same thing that Graydon explained even though you needed to ask me a question about it..... albeit a rhetorical one..... and from the many things I have read, such as from that link I posted from Scientific American, written by that Harvard physics professor, (not that I am pulling an appeal to authority card, since as state! d,! ! I've read this type of explanation from other sources) and for which I will just post right here for all to see...

"This behavior may seem at odds with our daily experience of throwing rocks into a sandbox or mud, because in those cases the shape and size of the 'crater' is dominated by the physical dimensions of the rigid impactor. In the case of astronomical impacts, though, the physical shape and direction of approach of the meteorite is insignificant compared with the tremendous kinetic energy that it carries.

An exception to this rule occurs only if the impact occurs at an extremely shallow, grazing angle. If the angle of impact is quite close to horizontal, the bottom, middle and top parts of the impacting asteroid will strike the surface at separate points spread out along a line. In this case, instead of the energy being deposited at a point, it will be released in an elongated zone--as if our 'bomb' had the shape of a long rod.

Hence, a crater will end up having an elongated or elliptical appearance only if the angle of impact is so shallow that different parts of the impactor strike the surface over a range of distances that is appreciable in comparison with the final size of the crater as a whole. Because the final crater may be as much as 100 times greater than the diameter of the impactor, this requires an impact at an angle of no more than a few degrees from horizontal. For this reason, the vast majority of impacts produce round or nearly round craters, just as is observed."

........... If you would have posted the rest of what came after "throwing rocks into mud".... instead of stopping there and telling me that "Chicxulub wasn't directly comparable to tossing a rock in mud.".....  in which the rest of the paragraph for which that mud sentence comes from and for which I posted, says in the next sentence or two that astronomical impacts indeed are not like throwing rocks into mud..... already stating what you felt the need to state about Chicxulub as if I was saying it was like throwing rocks into mud and you were saying I was wrong....... I wouldn't have felt the need to make sure that this horse was beaten into the ground this one last time..... posting that entire excerpt so that you and all could see what someone in the field has to say about the observed situation...... wasting my free time :-)

And by the way, "Because the final crater may be as much as 100 times greater than the diameter of the impactor, this requires an impact at an angle of no more than a few degrees from horizontal." This lends to the fact as to why Chicxulub appears the way that it appears... A horseshoe... But, as you rightly questioned before, it's not a prominent-looking one.

What can I say?..... I have a nasty habit of accepting direct, concrete observations, the experiments that show that the observations are indeed correct, and a habit of accepting the word of those with the expertise who work in the field on a daily basis..... I could be wrong about this practice of course...... I don't always agree with the experts. But, I have yet to run into a major snag while practicing it.......

And yes, as you said...... this was enlightening.... But... the horse is long dead and buried..... Enough is enough...... :-)