Freethought & Rationalism Archive

gallo · 08-05-2003, 05:38 PM

A lurker popped out of the woodwork to ask me this question on another board.

Quote:

Anyway, I saw something pro creationism that said that granite is a genisis rock and cannot be reproduced or something like that. It also said something like even the lava or magma that hardens will never be able to form granite only a rock very similar to granite (forgot the name) and Granite cannot be melted and then hardened back into granite only the rock that is similar. Their argument was that since granite cannot be reproduced in any of these ways it would have had to be created as is, solid, and not molten rock. I was wondering if you or anyone else for that matter has an explanation for this. Thanks for any info.

Isn't this kind of like pointing to a bottle of milk with the cream separated on top and claiming that God created the cream because it is impossible for it to form from the milk?

pmurray · 08-05-2003, 06:30 PM

I'm not sure I belive this (completely unsupported) claim. Seems to me there's be no trouble making granite from molten rock ... provided you could keep it at adequate temperature and pressure long enough for the separate crystals (quartz, feldspar, mica) to grow. Mother nature manages to do this by trapping it underground. Perhaps what the origanal person was saying was that molten granite does not re-form into granite on the surface, and some creationist blew it up into this bit of nonscience.

Doubting Didymus · 08-05-2003, 06:49 PM

I really don't understand this at all.

Coragyps · 08-05-2003, 07:05 PM

I've just been in a discussion (well, almost - the other guy hasn't answered my rebuttal yet) on this very topic. Granite and rhyolite are chemically the same thing - feldspar-rich rocks - that differ, AFAIK, only in how fast they crystallized. Granite solidified slowly, below the surface, and so has large crystals, while rhyolite cooled fast on or near surface and has fine crystals. Pretty much the same as the difference between ice on a lake and snow.

Now whether anyone has ever cooled molten granite slowly enough to get the same sized crystals they started with, I don't know. It may well take a very long time, and may need pressure as well. But it's not magical just because you cant make it in an afternoon on your kitchen stove.

This is odd, too: I've been following a lot of Creationist jive for two or three years now, and I hadn't seen this until last week. I'll bet we see a lot of "granite is Creation rock!" in the months to come.

conkermaniac · 08-05-2003, 07:17 PM

Doh...not all rocks are formed by cooled lava. :banghead: Any sixth-grader could tell this guy that there are three types of rock: igneous, sedimentary, and metamorphosis.

gallo · 08-05-2003, 07:24 PM

Doubting Didymus,

Me too. That's why I asked.

Coragyps,

Snyder, Texas? I can't count the times I passed through Snyder on my way from Houston to Lubbock. My son spent 7 years in Lubbock (two bachelors degrees from Tech and 6 credits short of M.Ed.) He taught there while working on his masters. He did get a masters degree elsewhere.

Anyway, back on topic.

I've been reading various stuff on the internet and I asked Joe Meert. It seems to me that what you say is correct. I knew before that the size of the crystals was an indication of the rate of cooling. I think this is the issue that troubles creationists. Large crystal granite indicates great age, so it must have been created by gawd.

Coragyps · 08-05-2003, 07:29 PM

Quote:

I can't count the times I passed through Snyder

I'm sorry.

gallo · 08-05-2003, 07:52 PM

Ah, yes. So is my son. He got a ticket there. :boohoo: Snyder has quite a reputation with Tech students. If you speed through Snyder, you will get a ticket - it is almost as sure as death and taxes. So I asked my son if he knew the cops were going to be there, why did he speed? His answer was, "stupidity."

Calzaer · 08-05-2003, 08:32 PM

Granite is an intrusive, felsic igneous rock formed by relatively slow cooling and crystalization of magma. It's made of primarily k-spar and quartz, with a bit of muscovite mica, and smaller quantities of biotite mica and amphibole. It certainly takes a long time to crystalize, which is why it's intrusive rather than extrusive, but to say magma will *never* form into it again is a completely daft statement. It takes just as long to form granite now as it did back in the cenozoic.

Quoting from my textbook:

Quote:

Partial melting is another process by which magmas of more than once composition can form. As rocks undergo partial melting, the early-formed (low-temperature) magma [the stuff that's close to being granite - Cal] may rise (due to convection) or otherwise separate from the solid portion of the rocks to produce a body of felsic magma [the stuff required for granite to form - Cal]. At higher temperatures, however, the remaining portions of the rocks may melt to produce a higher-temperature magma of intermediate composition. This is one way to explain how granitic magmas [magmas that produce granite - Cal] can evolve from a subducting mass of seafloor basalt

In short, granite is being formed RIGHT NOW.

Although, to be fair, the distinction between granite and porphoritic rhyolite sometimes seems subjective... but if this person (who whoever this person is parroting) really knew enough about geology to be confident in this statement, they'd be claiming PEGMATITE as the genesis rock, since it has to cool even slower than granite. If granite is a genesis rock, how the hell could pegmatite exist??

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08-05-2003, 06:30 PM	#2
pmurray Regular Member Join Date: Jul 2000 Location: Canberra, ACT, Australia Posts: 288	I'm not sure I belive this (completely unsupported) claim. Seems to me there's be no trouble making granite from molten rock ... provided you could keep it at adequate temperature and pressure long enough for the separate crystals (quartz, feldspar, mica) to grow. Mother nature manages to do this by trapping it underground. Perhaps what the origanal person was saying was that molten granite does not re-form into granite on the surface, and some creationist blew it up into this bit of nonscience.

08-05-2003, 06:49 PM	#3
Doubting Didymus Veteran Member Join Date: Jul 2002 Location: East Coast. Australia. Posts: 5,455	I really don't understand this at all.

08-05-2003, 07:05 PM	#4
Coragyps Veteran Join Date: Aug 2001 Location: Snyder,Texas,USA Posts: 4,411	I've just been in a discussion (well, almost - the other guy hasn't answered my rebuttal yet) on this very topic. Granite and rhyolite are chemically the same thing - feldspar-rich rocks - that differ, AFAIK, only in how fast they crystallized. Granite solidified slowly, below the surface, and so has large crystals, while rhyolite cooled fast on or near surface and has fine crystals. Pretty much the same as the difference between ice on a lake and snow. Now whether anyone has ever cooled molten granite slowly enough to get the same sized crystals they started with, I don't know. It may well take a very long time, and may need pressure as well. But it's not magical just because you cant make it in an afternoon on your kitchen stove. This is odd, too: I've been following a lot of Creationist jive for two or three years now, and I hadn't seen this until last week. I'll bet we see a lot of "granite is Creation rock!" in the months to come.

08-05-2003, 07:17 PM	#5
conkermaniac Senior Member Join Date: Jun 2003 Location: American in China Posts: 620	Doh...not all rocks are formed by cooled lava. :banghead: Any sixth-grader could tell this guy that there are three types of rock: igneous, sedimentary, and metamorphosis.

08-05-2003, 07:24 PM	#6
gallo Regular Member Join Date: Jun 2001 Location: Houston, TX, US Posts: 244	Doubting Didymus, Me too. That's why I asked. Coragyps, Snyder, Texas? I can't count the times I passed through Snyder on my way from Houston to Lubbock. My son spent 7 years in Lubbock (two bachelors degrees from Tech and 6 credits short of M.Ed.) He taught there while working on his masters. He did get a masters degree elsewhere. Anyway, back on topic. I've been reading various stuff on the internet and I asked Joe Meert. It seems to me that what you say is correct. I knew before that the size of the crystals was an indication of the rate of cooling. I think this is the issue that troubles creationists. Large crystal granite indicates great age, so it must have been created by gawd.

08-05-2003, 07:52 PM	#8
gallo Regular Member Join Date: Jun 2001 Location: Houston, TX, US Posts: 244	Ah, yes. So is my son. He got a ticket there. :boohoo: Snyder has quite a reputation with Tech students. If you speed through Snyder, you will get a ticket - it is almost as sure as death and taxes. So I asked my son if he knew the cops were going to be there, why did he speed? His answer was, "stupidity."

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