Download Polar wandering curve

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Continental drift and paleomagnetism
Magnetized minerals in rocks
Show the direction to Earth’s magnetic poles
Provide a means of determining their latitude of origin
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Figure 19.9 Earth’s magnetic field
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Remanent Magnetism
Figure 19.10 Inclination of dip needles at different places on the Earth’s surface
Def: The component of a rock’s magnetism induced by the
Earth’s magnetic field, when that rock is formed
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Thermoremanent Magnetism
TRM: igneous rocks
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Depositional Remanent Magnetism
DRM: sedimentary rocks
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“Polar wandering”
1950’s Runcorn and others
magnetic alignment of lava flows of different ages varied
significantly
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“Polar wandering curve”
Line on a map connecting the apparent positions of the magnetic poles through time
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“Polar wandering”
The term “Polar wandering” is a misnomer, since it’s the continents that are
“wandering”, not the poles!
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Polar wandering curve for the South Pole
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The scientific revolution begins
Fig. 19.11, p. 526
Harry Hess in the early 1960s
“Essay in Geopoetry”
Seafloor spreading hypothesis
Continents and ocean crust move together, and are parts of larger
plates
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The scientific revolution begins
Discovery of the mid-oceanic ridge system
parallel to continental margins
High heat flow and volcanism
Deep-sea trenches paralleled the continents
The ocean floor was no older than ~160 Ma
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Fig. 19.12, p. 527
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Geomagnetic reversals
Earth's magnetic field periodically reverses polarity
Fig. 19.13, p. 528
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Fig. 19.14, p. 528
Mapping of the ocean floor
During the 1950s and 1960s
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Geomagnetic reversals
Geomagnetic reversals also recorded in ocean crust
In 1963, Vine and Matthews combined
ocean floor magnetic stripes
+ Hess’ seafloor spreading
= PLATE TECTONIC THEORY
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Fig. 19.15, p. 529
Fig. 19.16, p. 530.
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Plate Tectonics
Def.: A theory that explains the behavior of the Earth’s lithosphere in terms of several moving plates.
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