Earth s magnetic field flow in the liquid outer core

 Earth ’ s Magnetic Field ! Flow in the liquid outer core creates the magnetic field. " It is
similar to the field produced by a bar magnet. " The magnetic pole is tilted ~11.5° from
the axis of rotation.
 Magnetic Poles ! The magnetic pole moves w.r.t the Earth ’ s surface. (i.e. Geographic and
magnetic poles are not parallel.) " Magnetic poles are located near geographic poles. "
Magnetic poles move constantly.
 The Earth ’ s Magnetic Field; A compass points to magnetic N, not geographic N. ! The
difference between geographic N and magnetic N is called declination. It depends on: "
Absolute position of the two poles #Geographic north #Magnetic north " Longitude
 The Earth ’ s Magnetic Field; Curved field lines cause a magnetic needle to tilt. ! Angle
between magnetic field line and surface of the Earth is called inclination. It depends on: "
Latitude
 Paleomagnetism; Rock magnetism can be measured in the laboratory. ! The study of
fossil magnetism is called paleomagnetism. ! Iron (Fe) minerals in rock preserve
information about the magnetic field at the time the rocks formed. " Declination and
inclination preserved in rocks often vary from present latitude / longitude. " Instruments
used in paleomagnetism record changes in position. " These data are used to trace
continental drift. ! Iron minerals archive the magnetic signal at formation. ! Hot magma "
High Temp — no magnetization #Thermal energy of atoms is very high. #Magnetic dipoles
are randomly oriented.

 Iron minerals archive the magnetic signal at formation. ! Cooled magma " Low Temp —
permanent magnetization #Thermal energy of atoms slows. #Dipoles align with Earth ’ s
magnetic field. #Magnetic dipoles become frozen in alignment with field.
 Polar Wandering; ! Layered basalts record magnetic changes over time. ! Inclination and
declination indicate change in position. ->
 Apparent Polar Wandering; Polar wandering paths were
initially misinterpreted: " Not the signature of a wandering
pole on a fixed continent " The signature of a fixed pole on a
wandering continent ->
 Polar Wandering; Each continent had a separate polar wandering path. Now understood
to represent that: " The location of the magnetic pole is fixed. " The continents
themselves have moved. ! These curves align when continents are reassembled.
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 Any substance that flows is a fluid. A solid, liquid or gas can all also be a fluid!!
 Fluid vs Liquid; Solid Fluid: The asthenosphere +Mesosphere (mantle below lithosphere)
Liquid Fluid: The ocean, or the outer core Gas Fluid: The atmosphere!
 Slides courtesy of Erik Chan, postdoctoral fellow at the McGill Space Institute:
I. Electromagnetism; How a generator/motor works: ‣ A charge moving through a
magnetic field feels a force ‣ i.e., a changing magnetic field generates an electric
current ‣ A moving electric charge (e.g. an electric current) generates a magnetic
field
II. The Earth ’ s Dynamo; Earth ’ s outer core: ‣ Liquid iron (a conductor) ‣ Convecting
to dissipate heat (electric current) ‣ Generates magnetic field ‣ Shaped in part by
Earth ’