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Quick Granite Formation

Posted by timothy on from the evolving-hypotheses dept.

Amphigory writes: "According to an article at Scientific American scientists now think that large granite formations could form in only a few thousands of years instead of the hundreds of thousands or even millions previously thought. This may have some really interesting implications for everything from geology to cosmology to evolution."

6 of 8 comments (clear)

  1. Yeah well... by pb · · Score: 3

    That's what happens when things get taken for granite...

    (sorry, couldn't resist!)
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  2. Let there be light by Anonymous Coward · · Score: 2

    Ah ha! The Devil thought he could make us doubt creation by burying dinosaur bones and making granite look like it took forever to form. We finally uncovered the subterfuge! 4000 years it is.

  3. Re:errrr this is not a small discovery... by tesserae · · Score: 2
    Well, except for the fact that granite is not a metamorphic rock...

    The big change is that it may not have taken millions of years for the initial granite crust to form. But since granite is the primary constituent of the crust, and the crust had to form before anything was done with it (like plate tectonics shoving it around), this just pushes the "start" line back a bit; it's not changing what the crust is made of, just how quickly it was emplaced. And considering that the oldest rocks are around 4 billion years old, this will turn out to be a change in maybe the fifth decimal place... not too serious, I think.

    Eventually the geology books will change; dunno 'bout the geography texts, though.

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  4. How profound are the implications? by hubie · · Score: 2
    It is not immediately clear to me how significant the implications of this are. Regardless of whether granite can form in such a quick manner, it still needs to be shown that the Earth's mantle did form in this manner. What do these results say about the isotopic dating calculated ages of the crust? Hopefully if one assumes that the continents formed in such a swift manner, this will point the field geologists in the right direction to look for further evidence. Any geologists care to comment?

    I am also not sure what the implications of these experiments have on cosmology. From a cosmological standpoint anything heavier than helium is not that important (unless the "missing mass" consists of blobs of granite floating around between the stars!). :)

  5. This is a middlin' small discovery. by Tau+Zero · · Score: 4
    so basically this is sending geologists back to square one in terms of how the earth's structure was formed.
    Not by a long shot. It takes geologists back a couple of orders of magnitude about how long it takes granite intrusions to move into place. It doesn't change anything about how long it takes crystals of a given size to form, nor about how long it's been since different rocks crystallized; if anything, potassium-argon dating (which depends on the decay rate of K-40 into Ar-40 and the fact that molten rocks hold potassium but not argon), uranium-lead dating, and other radiometric methods keep getting more and more solid as the confirming data piles up. If there were something wrong with the dating methods, you'd see more and more evidence of inconsistency as the data accumulated. I've heard nothing to indicate that.
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  6. Re:errrr this is not a small discovery... by Rei · · Score: 2

    This research is blatantly wrong, and I have to question either a) the researcher, or b) the accuracy of the publication in relating to the original work. When the magma that forms granite cools quickly, what you get isn't granite, but rhyolite. Granite is what you get when it cools slowly. The difference is the crystal size and structure. There are places on earth where granite is forming - they're huge, and underground (and, often harnessable for geothermal energy). Any intrusion which would allow the granite to get to the surface quickly would only produce rhyolite. Even if *all* *granite* was formed from these rapid formations, you'd still have one huge issue on your hands: cooling. Granites average about 900 degrees celcius at their peak temperature as magma (the peak temperature can be determined from the crystal structure, as evidenced in laboratory work). Granite is also a horrible conductor of heat. The initial estimates of how long it took a granite range to form were not based on the speed of magma flows, but from the size of the ranges and the temperature they were formed at. Even if they were formed in little bits from rapid movement, the total time to cool would still be in the millions of years. But, they aren't, so its a moot point ;) - Rei

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