Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Earth's Magnetic Field and Core

  1. Oct 23, 2014 #1
    Given the increase in geophysical phenomena (such as earthquakes and volcanic eruptions), it is obvious "something" IS going on with our planet. I have no trouble believing in this theory that a reversal of the earth's magnetic field may be included -- sooner as opposed to later.

    However, no one has been able to satisfactorily explain to me the following contradiction:

    It is said the earth's magnetic field derives from its iron core;

    furthermore, due to supposedly the intense pressures and temperatures at the center of the earth, this core is said to be a MOLTEN iron core;

    yet if a magnet is HEATED, it LOSES its magnetic characteristics and properties.

    "above a certain temperature ("Curie point"), iron loses all its magnetism"


    When a magnetic material reaches its curie temperature point and supposedly the magnetic moments are jumbled up no longer uniform aligned, as inter-related as magnetic and electrical fields are, it should result in corresponding jumbling of the associated electrical fields as well.

    Yet, we have the dynamo theory that is said to explain this.


    As I understand the dynamo theory, electrically conducting material, even though at or above the curie temperature and therefore having lost "internal magnetism", but still capable of "conducting electrically" produce enough electrical current activity to generate an "external" magnetic field.

    Yet, electrical current flows best at super COLD temperatures ("super conductors" due to lack of resistance), and heat INCREASES resistance to electrical flow.

    But magnetic materials, having lost their "internal magnetic" properties due to at or above their curie temperatures, are still said to realign magnetic domains under the influence of an EXTERNAL magnetic field; as applied to the planet earth, such would have to come from the sun.

    So, perhaps the earth's magnetic field is only indirectly resultant from an iron external/internal core (molten or otherwise), and more directly resultant from the solar magnetic field itself instead.

    I think a Noble prize in physics for pointing this out is in order; but I imagine someone else will get the credit and the million bucks.



    Last edited: Oct 23, 2014
  2. jcsd
  3. Oct 23, 2014 #2

    D H

    User Avatar
    Staff Emeritus
    Science Advisor

    Whoa there! What increase in geophysical phenomena?

    It looks like there are a lot more hurricanes now than 100 years ago. This is not the case. We simply observe a lot more than hurricanes than we used to. Most hurricanes never come close to land. Until we had satellites, meteorologists didn't have a clue of the number of hurricanes per year. When you look at the number of severe hurricanes that hit land, that number doesn't appear to have changed that much.

    The same pertains to much of the earth sciences. Technology has enabled earth scientists to see more stuff, and to see it more quickly. Consider the Tambora eruption of 1815, the biggest volcanic event in the last 1,000 years. New of this singular event traveled slowly because the only means of long distance communications were hand-written letters carried by ships.

    There has been one VEI 5 or higher eruption in the 21st century. There were twelve in the 20th century, one every eight years. One large eruption in fifteen years doesn't look that ominous. The same goes for earthquakes. Geologists are indeed seeing a good number more small earthquakes than in previous centuries, but that's only because modern technology enables them to detect those small earthquakes from the comfort of their offices. This increase vanishes when you look at large earthquakes.

    So what is this increase in geophysical phenomena of which you write?
  4. Oct 23, 2014 #3
    I agree that modern technology has improved our ability to measure activity and events, and modern media including the internet promotes information distribution.

    But current events indicate an increase in geophysical activity; much more volcanic eruptions (volcanoes long dormant going active) and earthquakes as well, even if they may be smaller than the major quakes of recorded history.

    In the central USA, earthquakes were so uncommon to be almost unheard of, until recently - Oklahoma has had a rash of them within the last few years/months.



    Yellowstone (on top of a major long dormant volcano) is heating up; much speculation in the media (even National Geographic magazine) has done articles speculating if it is going to blow; new geysers are erupting all over the place.


    The earthquakes in the Middle East, China, and Pacific Rim seem to be on the increase.

    But these things seem to have their cycles, and as young as the 21st century is, comparison to the 20th century or other periods of history is not totally comprehensive.
  5. Oct 24, 2014 #4
    Looking at the wiki article, it is not current through the conductive material, but convective current of magma (presumably ionized) that cause the magnetic field.
  6. Oct 24, 2014 #5
    Why should that convective current change direction from time to time? What causes that?
  7. Oct 24, 2014 #6
    After reading a few wiki articles, I would say anybody's theory would be as good as the ones listed in the articles.
    It seems there does have to be a conducting fluid - but nothing has been successfully modeled yet.
  8. Oct 24, 2014 #7


    User Avatar
    Science Advisor
    Gold Member
    2017 Award

    you seem to have a number of misunderstandings ...
    and this above is yet another one

    the iron core is not molten ... its solid and is surrounded by a "liquid" outer core
    the magnetic field is generated primarily by the interaction between the two of them
    google magneto hydro dynamics

    you really believe that ?

    then explain Venus ... its closer to the sun than us, it should have a bigger magnetic field !

    instead it has no planetary wide magnetic field. The very weak magnetic field that is present on Venus is caused by the interaction of the solar wind and the ionosphere. As the solar wind flows past the planet, the particles within the solar wind ionize the gasses in the upper atmosphere. These ionized gasses are now charged and can induce a weak magnetic field through the motions of the gas and wind around the planet.

    Yellowstone sits over a hotspot, much like Hawaii does, just isn't so regularly active. Rather it tends to do major blasts at long intervals

    again you are not reading the info.
    99% of those quakes are man induced ... google fracking - fluid injection

    they are NOT natural events

    you haven't given any evidence to support that statement

    the long term averages for moderate to large events hasn't changes significantly since seismic recording began

    http://earthquake.usgs.gov/earthquakes/eqarchives/year/eqstats.php [Broken]

    8+ .... 1 / yr
    7-7.9 ..... 15/yr
    6-6.9 .... 134/yr

    2007 was one year that did stand out from the norm with 4 events of M 8+

    Last edited by a moderator: May 7, 2017
  9. Oct 24, 2014 #8


    User Avatar

    Staff: Mentor

    Thread closed for Moderation...

    EDIT -- Thread will remain closed.
    Last edited: Oct 28, 2014
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook