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Posted

it is good that you no longer drink then. I have done silly things, but I never loose controle. I just don't drink that much.

 

checking out link now [big Grin]

 

[ 10-19-2002, 11:30 PM: Message edited by: Muffy The Wanker Sprayer ]

Posted

Most basalt is columnar, meaning it has vertical cracks. As the basaltic lava cools it must contract. It's quite easy for it to contract in the vertical direction, the flow merely gets "shorter" or thinnner as it cools. However, in the horizontal dimensions it cannot "shrink" because the flow is too large to overcome the shear stresses at it's base, therefore it cracks into collumns to accomodate the contraction due to cooling. Why these things crack into such perfectly polygonal shapes is not understood, and rather counter-intuitive when thought about from the perspective of fracture propogation (i.e. once a fracture starts propogating it should continue indefinitely in the direction that it initiated until intersecting a barrier).

 

The second link I gave outlines the SJ Gould article rather well, but it's not nearly as well written. I'm leaving it up to Fern to find a copy of the original. I'm tired and going home.

Gonna stop in my office to lock up and say good-night then I'm outta here.

Posted

thanks for all the great info [big Grin] and my education continues... have a great night [big Grin]

 

BTW I am still reading about the great flood. Interesting... about the "uninformation" makes one stop and think about alot of things, no?

Posted

I believe columnar basalt cracks in hexagonals mirroring the underlying crystal lattice structure formed from Si MG and O2. Microscopic structure reconstructed at the macro level. Just got back from climbing on some slightly andesitic basalt (beacon baby beacon!) [Razz]

Posted

and now it's off to glisse and ice climb on some crystallized H20 on a chossy dormant stratovolcano, but first breakfast at T-line (salmon hash salmon hash salmon hash!)

Posted

quote:

Originally posted by iain:

I believe columnar basalt cracks in hexagonals mirroring the underlying crystal lattice structure formed from Si MG and O2. Microscopic structure reconstructed at the macro level. Just got back from climbing on some slightly andesitic basalt (beacon baby beacon!)
[Razz]

Nice try, Iain but, it's not. The mineralogy of Basalt is totally random (and primarily Ca-Feldspar anyway, which isn't hexagonal). Columnar jointing has nothing to do with the macroscopic expression of the internal micro-structure. But I can see how people might think so.

 

[ 10-20-2002, 12:09 AM: Message edited by: E-rock ]

Posted

Hehe I know I am just talking out my ass at this late hour and am still slightly enibreated. [big Grin] Believe it or not from that last post, but I do have degrees in geology and biology I just choose not to use them at this juncture. [laf]

Posted

I think I should be issued a degree in child reering and laundry [Razz]

 

has anyone ever mentiond to any of you that you might be over educated??? [Wink][Razz]

Posted

Good night everyone, it's been fun (a better substitute for climbing than I had hoped).

 

And Muffy, the uniformitarian debate I think is one of the more interesting ones in scientific philosophy. One of the big questions that my old Sed-Stat professor used to like to ask was:

 

Is the sedimentary record representative of normal sedimentary events, or are only the really BIG events preserved?

 

Food for thought... The sahara desert sands are on the order of tens of meters thick. The Navajo sandstone is on the order of 100 to 1000m thick.

Posted

quote:

Originally posted by E-rock:

Food for thought... The sahara desert sands are on the order of tens of meters thick. The Navajo sandstone is on the order of 100 to 1000m thick.

So what are you suggesting, that climates were extremely different in the Mesozoic? Of course! [smile] The Navajo Erg explanation was good enough for me. (I think the Navajo tops out at 700-something meters but I'm rusty on that strata).

Posted

I am soooooooo bored!!!!!!! every one especialy iceguy should check their pm's... and log on you lurkers.... I want to know who is arround [Razz]

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