earthquakes 3

earthquakes 3 - paleomagnetism: works on magnetic field....

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paleomagnetism: works on magnetic field. earth's magnetic field looks similar to an magnetic iron bar - due to dynamo action because of the iron in earth's core. certain types of minerals in rocks that have particular iron atoms that at certian temperatures, they become aligned. -at a temp above curie point, magnetic domains are randomly oriented with no net magnetization. - magnetic mineral grain has cooled to a temperature below the curie point in the presence of the earth's magnetic field. magnetic domains hten line up according to the earth's field. - works with sediments or lava. studied to tell earth's magnetic field in different times and measure changes by going down the core to measure the orientation. recent measurements of field always point to north pole and estimate site latitude. - very small changes around the current north pole. - as we studied older rocks (200 million years), the north geographic pole is far far far away. paleomagnetic studies of some older rocks suggest pole positions have 'changed systemically over time. - either continents have moved OR north pole has moved.
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earthquakes 3 - paleomagnetism: works on magnetic field....

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