GEO 303 Lecture Notes - Lecture 3: North Magnetic Pole, Geomagnetic Reversal, Dynamo Theory
11 Nov 2016
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Document Summary
Careful measurements of the earth"s magnetic field have given us an idea of its variation in the past. Over the past 100 years, the magnetic north pole has moved over 1200 km: earth"s magnetic field strength. Earth"s magnetic field acts as a dipole but field weakens and strengthens over time: earth"s magnetic field reversal. Earth"s magnetic field acts as a dipole but it periodically reverses polarity. Origin of earth magnetism: the geodynamo. Normal and reversed polarity signatures are non-unique: require stratigraphic correlation and tie points. Can read the age of the ocean floor by reading magnetic stripes. Over millions of years polar wander is mostly due to continents moving. Black: path of north pole computed from north american rocks. White: path of north pole computed from european rocks. Left: assumes continents are fixed and pole movement due to polar wander. Right: assumes pole fixed and that the apparent movement of the pole is due to the movement of continents.
