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View Diary: DKos Special Supplement: Plate Tectonics And The World’s Changing Geography (Part 2 of 2) (68 comments)

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  •  The magnetic field of Earth is present because of (2+ / 0-)
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    RiveroftheWest, mightymouse

    the iron-nickel liquid outer core. The magnetic field does vary in intensity over time and undergoes reversals in polarity 3-4 times per million years. These reversals have been preserved in the iron-bearing minerals found in lava flows. Detection of the record of polar reversals in sea floor basalts provided one of the first compelling pieces of evidence for the plate tectonic theory.

    I am not aware that the current rate of magnetic variation is anything but ordinary.  

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