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Liquid Regions of Mantle May Underlie Plumes

  1. Jul 29, 2017 #1

    BillTre

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    A news article in Science magazine discusses seizmic ultralow-velocity zones (800 km across x 15 km tall).
    Some people think the seizmic ultralow-velocity zones could be liquid.
    They are thought to underlie rising mantle plumes.
     
  2. jcsd
  3. Jul 30, 2017 #2

    davenn

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    hmmmm a couple of new thoughts :smile: But the overall idea as said has been known for some time

    interesting contradiction ... the mantle isn't really solid

    ohhh BTW, its seismic, not seizmic :wink:


    Dave
     
  4. Jul 31, 2017 #3
    The mantle is solid dave! Otherwise how would shear waves go through? It's not rigid, and deforms visco-plastically, but it is solid!
     
  5. Jul 31, 2017 #4
    BTW, interesting topic and nice study... I will report back once I've had time to read the actual paper.

    EDIT: added a brief report.

    Ok so the seismology is very convincing. There is definitely something down there right at the base of the Iceland plume, and that something is definitely slow. Furthermore, the geometry of this feature is pretty well constrained to first order: it's a short and stout cylinder.

    The interpretation becomes a bit muddier and the authors are a bit overconfident in suggesting it to be melt.
    It could be partially molten material (imagine porous rock with a few % of melt -- don't make the common misconception of imagining it to be pure melt). Or it could be a pure solid with an iron-rich composition. Either model could explain the data equally well by making seismic waves travel slowly, and it is the author's tastes that lend them to side with the melt interpretation.
     
    Last edited: Jul 31, 2017
  6. Jul 31, 2017 #5

    davenn

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    not solid as in the crust .... it is very pliable ... I WASNT inferring it was totally liquid .... am not that stupid
     
  7. Aug 2, 2017 #6
    Dave I know you know and by no means was challenging your clearly very high intelligence! :smile:

    I just wanted to make sure, for the record, that no one came away with the misunderstanding that the mantle was in any way not a solid. It's a common misconception. I remember, I was taught in a high-school text book that the mantle was liquid and that's why you got molten lava coming out of volcanoes! Wrong wrong wrong! LOL Just want to put that myth to bed once and for all!
     
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