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posted by Fnord666 on Wednesday January 02 2019, @05:25PM   Printer-friendly [Skip to comment(s)]
from the someone-removed-the-crust dept.

Submitted via IRC for Bytram

Earth is missing a huge part of its crust. Now we may know why.

According to the team, at intervals within those billion or so years, up to a third of Earth's crust was sawn off by Snowball Earth's roaming glaciers and their erosive capabilities. The resulting sediment was dumped into the slush-covered oceans, where it was then sucked into the mantle by subducting tectonic plates. (Here's what will happen when Earth's tectonic plates grind to a halt.)

AND

What could have wiped 3km of rock off the entire Earth?

Believe it or not, the geology at the bottom of the Grand Canyon is extraordinarily common. There, layers of sedimentary rock lie flat atop angled layers of significantly more ancient metamorphic rock. The gap there is enormous—if Earth's rocks constitute a book of the planet's history, there are about a billion pages missing. The story only picks up again around 540 million years ago in the Cambrian period, with an evolutionary explosion of complex life just as remarkable as the sudden change in the rock.

This gap can be found all around the world, and has picked up the name the Great Unconformity. Cambrian sedimentary rocks rarely rest on anything other than much older metamorphic or igneous rock, implying that whatever rock formed in the intervening time was scrubbed away by something. This erasure of a chunk of geologic history has long been an enticing mystery for geologists.

A period of intensive global erosion doesn't seem sufficient to fully explain the pattern of change in the rock. An alternative, that the formation of new rock suddenly accelerated beginning in the Cambrian, doesn't quite fit the evidence, either. So what gives?

PNAS, 2018. DOI: 10.1073/pnas.180435011  (About DOIs).


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  • (Score: 2) by Hartree on Wednesday January 02 2019, @05:28PM (7 children)

    by Hartree (195) on Wednesday January 02 2019, @05:28PM (#781094)

    That's where the space aliens deleted the evidence of the advanced civilization they wiped out so us monkey boys could take over.

    • (Score: 2) by Runaway1956 on Wednesday January 02 2019, @05:34PM (5 children)

      by Runaway1956 (2926) Subscriber Badge on Wednesday January 02 2019, @05:34PM (#781097) Homepage Journal

      But, it's still not "missing". It's right beneath our feet, in the mantle. That history you mention has been bent, folded, spindled, and mutilated, but it's still just beneath our feet!

      --
      Let's go Brandon!
      • (Score: 0) by Anonymous Coward on Wednesday January 02 2019, @05:49PM (4 children)

        by Anonymous Coward on Wednesday January 02 2019, @05:49PM (#781100)

        A large segment of that geology has been scraped out between the two layers of known geological history. The statement is that it was cleaved out by a massive ice age that ground up the crust which was then sucked between the continental plates and is somewhere in the mantle now.

        Or as someone else suggested, aliens needed to scrub out the history of the former inhabitants of Earth.

        • (Score: 2) by Runaway1956 on Wednesday January 02 2019, @06:47PM (3 children)

          by Runaway1956 (2926) Subscriber Badge on Wednesday January 02 2019, @06:47PM (#781116) Homepage Journal

          I'll repeat - it's not "missing". It has merely been made illegible to us, and it's right there beneath our feet. Remember the laws of conservation of energy and matter?

          --
          Let's go Brandon!
          • (Score: 0) by Anonymous Coward on Wednesday January 02 2019, @11:18PM

            by Anonymous Coward on Wednesday January 02 2019, @11:18PM (#781234)

            Your expansive definition means nothing material that existed once can ever be "missing."
            It kind of renders the word meaningless.

            Example: Wife leaves behind slice of chocolate cake. Parent poster steps in kitchen and eats it. Wife next morning says cake is missing. Parent poster denies it forcefully, knowing but not revealing that the cake is now in the form of a fecal slurry diluted by a factor of a billion being further destroyed by chorine disinfectant dozens of miles away at the sewage treatment plant.

            Lesson: "missing" has a real meaning that is context dependent.

          • (Score: 0) by Anonymous Coward on Wednesday January 02 2019, @11:48PM (1 child)

            by Anonymous Coward on Wednesday January 02 2019, @11:48PM (#781248)

            But the "history" we're referring to isn't energy or matter, it's information. When you scrub a hard drive, the rust is still there, but the data it previously stored is gone. It's absurd to say the data is still there, and has "merely been made illegible" -- and it's equally absurd to say that when speaking of geological history.

            • (Score: 0) by Anonymous Coward on Wednesday January 02 2019, @11:55PM

              by Anonymous Coward on Wednesday January 02 2019, @11:55PM (#781251)

              More to the point, "missing" means you know something should be there but it is not.
              It doesn't matter if the thing still exists in some form or not. "Missing" describes state of knowledge (a
              consciously incomplete knowledge) on the part of the person who declares something is missing. It declares that there is a mystery to be solved.

    • (Score: 2) by krishnoid on Wednesday January 02 2019, @09:28PM

      by krishnoid (1156) on Wednesday January 02 2019, @09:28PM (#781196)

      Wrong, wrong, wrong. Aliens or monkeys, the crust is always the most delicious part, which is why it went so long ago.

  • (Score: 2) by aiwarrior on Wednesday January 02 2019, @05:31PM

    by aiwarrior (1812) on Wednesday January 02 2019, @05:31PM (#781096) Journal

    It is amazing that through the power of deduction, not unlike a detective we can infer on effects and events that happened several million years ago, when there were not even vertebrates, much less humans.
    We are indeed the culmination of evolution in this planet and surroundings.

  • (Score: 1) by Snort on Wednesday January 02 2019, @07:47PM

    by Snort (5141) on Wednesday January 02 2019, @07:47PM (#781133)

    before the PR push.

  • (Score: 0) by Anonymous Coward on Wednesday January 02 2019, @10:03PM

    by Anonymous Coward on Wednesday January 02 2019, @10:03PM (#781209)

    Where did it go? It fell off the edge, of course. #FlatEarthSociety

  • (Score: 2) by legont on Thursday January 03 2019, @02:59AM

    by legont (4179) on Thursday January 03 2019, @02:59AM (#781347)

    They came, cleaned up the place, and seeded all the life. For whom? Well, probably for us. We, humans, are not likely from this planet. We are from a smaller planet with a dimmer star; based on our issues with solar radiation and locomotor system.

    --
    "Wealth is the relentless enemy of understanding" - John Kenneth Galbraith.
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