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Volcanos and magnetic field

  1. Feb 6, 2009 #1
    Are there any correlations of vulcanic activity and the strength of the earth magnetic field in earth history?
  2. jcsd
  3. Feb 7, 2009 #2
    Perhaps. For the late Pleistocene, there are good records for both. Guyodo and Valet 1999 and the volcanic markers in the ice cores

    It seems that there was increased volcanic activity both during the Laschamp and Blake geomagnetic excursion around 40,000 years ago. But there have also been periods with increased volcanims without magnetic anomalities, for instance sone 12-10,000 years ago.
  4. May 2, 2011 #3


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    [PLAIN]http://thetruthbehindthescenes.files.wordpress.com/2011/05/prtscr-capture.jpg [Broken]



    Here are a screen shot and two videos of recent (April 28-30, 2011) eruptions of Sakurajima volcano. In addition to the ordinary lightning bolts seen in the eruptions there are what appear to be additional electric or magnetic peculiarities. I have no idea what it exactly means with respect to Earth's magnetic field, but it might well be tentatively filed in this thread.

    Anyway, as a fan of loud noises, stinky smoke, explosions and intense electrical events, I think I'm in good company.

    Respectfully submitted,
    Last edited by a moderator: May 5, 2017
  5. May 3, 2011 #4
    Hi Steve,

    that's interesting. Thanks for the information!
  6. May 4, 2011 #5
    Active volcanoes are typically associated with a perturbation in the magnetic field *strangely* due to the lack of any contribution from the geology. That is because magma is above the Curie temperature -- the temperature above which a material cannot hold its ferromagnetism. This is a local effect. This is an effect of the magentic field component derived from the crust. The first order dipole magnetic field is derived from the earth's outer core. Note that changes in the Earth's outer core would almost immediately be expressed in the geomagnetic field, yet it would take of the order of 100 million years for those heat perturbations to convect to the surface to cause volcanism. Therefore, if there were a correlation, on the global scale, one would expect that there would be a 100 million year lag between the phenomena.
  7. May 4, 2011 #6
    But is heat convection the only way to transmit 'changes' in the outer coure? Seismic waves take minutes. What would the transmission speed be of mechanical changes in the outer core, like changes in pressure on the core mantle boundary, maybe due to precession differences between core and mantle?
  8. May 5, 2011 #7
    The sun's magnetic streamlines get through the earth, as far as I know (and I'm not a geolist ;-)). Well, lava contains some iron and other metallic stuff. Anyway, are there any arguments, that a mangetic field (like the one caused by the sun or the earth) cannot cause movements in hot lava and it's magnetic particles? It's just an idea and not very vell reasonded!
  9. May 5, 2011 #8


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    It would appear that the degree of charge separation in magma might have something to do with the answer to Tanja's question.

    Culled from a google search for "charge separation in magma" is a reasonably solid-looking piece of research into the recent lightning activity in an Icelandic volcano eruption. It includes references to additional papers on the subject of volcanic lightning.

    The authors seem to conclude that in this case charge separation occurs in the plume and at the vent. They seem to think that water content of the plume and local atmospheric conditions may affect the quantity of lightning strokes discharged in the plume.

    It's likely more educated forum members than I would draw better insights from these science papers - and I hope they would do so.

    Respectfully submitted,
  10. May 5, 2011 #9
    Seismic waves are not a good way to transfer heat. Also earthquakes aren't generated that deep in the Earth.

    But then heat doesn't necessarily have to travel from core to mantle. Alternatively something could be heating both areas simultaneously.

    Precession effects have been estimated to contribute 10^12 W of dissipation in the core, which is supposedly enough energy alone to sustain the geodynamo. Not sure of the numbers in the upper mantle, but is it possible that precession cycles could heat the upper mantle enough to trigger volcanism? If so then you have a mechanism that may establish a possible link.

    Anyone looked at any actual data to establish if there is a link or not yet?
  11. May 5, 2011 #10
    Undoubtedly this is an effect.

    Just to review the outline of the discussion:

    It appears that we have magnetic effects related to volcanism at various scales.

    (1) Local, during an eruption. Lightning in the ash cloud would be associated with strong local magnetic field changes.

    (2) Local, over the active lifetime of a volcano. Magma in the magma chamber would cause a local anomaly.

    (3) Global, over geological time. Changes in the outer core cause changes in the global magnetic field; changes in the upper mantle cause changes in volcanism.

    Effects (1) and (2) are fairly well understood. The third one is arguably the most interesting.
  12. May 6, 2011 #11
    "The sun's magnetic streamlines get through the earth, as far as I know..."

    IIRC, the Earth's own magnetic field usually blocks them. They may only do so during magnetic reversals, in the regions between the multi-poles...
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