Lecture18_magnetism - 1. The Earth has not always had its...

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1. The Earth has not always had its present polarity (normal) with north magnetic pole close to the north geographic pole. 2. Rocks can record the Earth’s past magnetic field (paleomagnetism).
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Needles, which are themselves magnets, are aligned with the earth’s magnetic lines of force. The needle has a north-seeking end (black) and south-seeking end (white). No matter how complexly shaped, every magnetic line of force is a closed loop. Lines may lie both within the earth and occupy the space surrounding the earth. Fig. 21-1
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At any point and time, the Earth's magnetic field is characterized by a direction and intensity which can be measured. The parameters measured are strength and direction of the field.
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Variation in geomagnetic total intensity for the last 400 years. 1600
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Variation in geomagnetic total intensity for the last 400 years. 1700
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intensity for the last 400 years. 1800
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This note was uploaded on 07/07/2010 for the course GEO geo taught by Professor Long during the Spring '10 term at University of Texas at Austin.

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Lecture18_magnetism - 1. The Earth has not always had its...

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