Total Pageviews

Tuesday, March 31, 2015

Slab Melting: Quite Continental!

       Plate tectonics theory has generally espoused that all continental crust, rich in silica, has been recycled. 


     Virginia Technical University geologists have published research today indicating some of that continental crust may actually be new or "juvenile" crust.

       Some of the type areas for this discovery are in Costa Rica and Panama:



The March 31, 2015, research includes this description of continental and oceanic crust:

     "The researchers used geochemical and geophysical data to reconstruct the evolution what is now Costa Rica and Panama, which was generated when two oceanic plates collided and melted iron- and magnesium-rich oceanic crust over the past 70 million years."

      "Melting of the oceanic crust originally produced what today are the Galapagos islands, reproducing Achaean-like conditions to provide the "missing ingredient" in the generation of continental crust."

     "The researchers discovered the geochemical signature of erupted lavas reached continental crust-like composition about 10 million years ago. They tested the material and observed seismic waves traveling through the crust at velocities closer to the ones observed in continental crust worldwide."



        The study continues "It raises questions about the global impact newly generated continental crust has had over the ages, and the role it has played in the evolution of not just continents, but life itself. 

        For example, the formation of the Central American land bridge resulted in the closure of the seaway, which changed how the ocean circulated, separated marine species, and had a powerful impact on the climate on the planet."




        Older names for continental and oceanic crust are SIAL and SIMA, respectively. Sial is a short for silica aluminum (or aluminum silicate) and sima is short for silica magnesium (or magnesium silicate). The sial is less dense than the sima. And now, researchers have shown that some of that sial is juvenile. 

SIAL LATER!

Steph




        

19 comments:

  1. Steph,

    This paragraph is why I never could have been a geologist:

    "This is an interesting paper that makes the case that andesitic melts inferred to derive ultimately by melting of subducted slabs in some modern arcs are a good match for the composition of the average continental crust," said Roberta L. Rudnick, a Distinguished University Professor and chair of the Department of Geology at the University of Maryland,

    Huh?

    It’s like the earth is a big ball of dough cooking in the oven. You take it out occasionally, spritz it with water, inject it with sugar and salt, shove it back into the heat, let it bake and remold itself, take it out, knead it a bit even after the crust has begun to form, reshove it ovenward, let the crust and crumb reach their doughy equilibrium…

    We are just mold on the loaf.

    LegoContinentalDrifter

    ReplyDelete
    Replies
    1. Lego, your paragraph indicates to me you'd make a great geologist! You have a good feel for earth dough.

      Delete
  2. Replies
    1. I'm not sure the monorail is such a good idea. It might be Smith's first step down the slipper slope toward becoming a Mickey Mouse school.

      L-e-g o-e-L a-m-b-d-a

      Delete
    2. Indeed, Lego. Was "slipper" slope a Freudian slip?

      Delete
    3. I think that, subconsciously, because I doubted that slipperier (slipperyer?) was not a real word, I was afraid I would misspell it. (A fear unfounded, however, because it is impossible to misspell non-existent words.) J.R.R. Toklien might have called this a Frodoan Slope, or Tolkien Trope.

      LegoFrodoBilbo

      Delete
    4. Tis a slippery slope indeed. I thought you might be heading for Ladies' Slippers, a favorite New England woodsy flower.

      By the way, two river otters have appeared on campus in Paradise Pond. A first spotting, as far as we know.

      Delete
    5. Are they a mated pair? Or are they just significant otters?

      Delete
    6. I otter know that would come up. The biologists say mated pair.

      Delete
    7. I otter know that would come up. The biologists say mated pair.

      Delete
  3. I'm having a hard time swallowing those stories, but it may just be my SIALadenitis acting up....

    ReplyDelete
    Replies
    1. Makes me salivate hearing about it, jan. . .

      Delete
  4. Steph, let me know if you're not planning to do the Cox/Rathvon acrostic in Sunday's NY Times. You wouldn't want to miss this quotation.

    ReplyDelete
    Replies
    1. After looking it over on Amazon, I don't think you'd want to miss the book from which the quotation was lifted, either.

      Delete
    2. I am not planning to do the acrostic. What's the quote?

      Delete
  5. "Three brothers inherited parcels of land from their father and wanted to combine them into one ranch. They didn't know what to name their ranch until their mother suggested: 'Focus -- it's where the mourning sons raise meat.'"

    It's from "Words Gone Wild," by Jim Bernhard, 2010. My library network doesn't have it, so I ordered a copy from Amazon.

    ReplyDelete
  6. Yawn, yawn, yawn: newest post is up!

    ReplyDelete