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20 Cards in this Set
- Front
- Back
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What is the magnetic field determined by?
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Convection currents in the outer core
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What generates electricity in the outer core?
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Self-exciting dynamo
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Why do metals in the outer core keep their magentism?
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They are above the curie point
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Why is the Earth's magnetic field not permanent?
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Metals in the outer core are above the curie point
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What causes the poles to change?
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Run down of the self moving dynamo as convection changes
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What type of minerals allign themselves with the Earths magnetic field?
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Iron rich minerals
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As metals cool below the Curie point they retain what?
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Their magnetism
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What is the age of lavas determined by?
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Radiometric dating
Fossils in the same bedding |
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Where is remenant magnetism often seen?
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Ocean floors
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How do we identify remenant magnetism?
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Aerial surveys
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What picks up the strength of the magnetic field?
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Magnetometers
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Above the zones of reversed polarity measurements are?
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Weak
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How do we find the lattitude of a volcano at the time of eruption?
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Magnetic inclination
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Rocks in Europe and North america show what about magnetic poles?
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North pole was in 2 positions at the same time
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What are plotted to show the movement of poles?
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Polar wondering curves
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Polar wondering curves are evidence for what 2 things?
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Continental drift
Polar wandering |
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'Ancient magnetism preserved in rocks'
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Paleomagnetism
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'A value for the Earth's magnetic field that is different from the expected value'
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Magnetic anomaly
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'Angle of dip of the lines of a magnetic field. It is the angle with the horizontal made by a compass needle'
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Magnetic inclination
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'Magnetism shown by rocks due to the allignment of their magnetic minerals according to the Earth's magnetic field at the time of formation'
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Remenant magnetism
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