| Abstract: | Direct measurements of the direction and strength of the earth‘s magnetic field have provided a knowledge of the field‘s form and behavior during the last few hundreds of years. For older times, however, it has been necessary to measure the magnetism of certain rocks to learn what the geomagnetic field was like. For example, when a lava flow solidifies (at temperatures near 1000??C) and cools through the Curie point of the magnetic minerals contained in it (around 500??C) it acquires a remanent magnetism that is (1) very weak, (2) very stablel, (3) paralle to the direction of the ambient geomagnetic field, and (4) proportional in intensity to the ambient field. Separating, by various analytical means, this magnetization from other ‘unwanted‘ magnetizations has allowed paleomagnetists to study the historical and prehistorical behavior of the earth‘s field. It has been learned, for example, that the strength of the field was almost twice its present value 2000 years ago and that it has often completely reversed its polarity. Paleo-magnetists have also confirmed that most oceans are, geologically speaking, relatively new features, and that the continents have markedly changed their positions over the surface of the earth. ?? 1969 The American Institute of Physics. |
| Genre: | Article |
| ProdID: | 70001684 |
| Citation Author: | Doell, R. R. |
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| Citation End Page: | 954 |
| Citation Issue: | 3 |
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| Citation Language: | English |
| Citation Larger Work Title: | Journal of Applied Physics |
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| Citation Search Results Text: | History of the geomagnetic field; 1969; Article; Journal; Journal of Applied Physics; Doell, R. R. |
| Citation Start Page: | 945 |
| Citation Volume: | 40 |
| Citation Year: | 1969 |
| Type: | citation/reference |
| Text: | History of the geomagnetic field; 1969; Article; Journal; Journal of Applied Physics; Doell, R. R. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| URL (DIGITAL OBJECT IDENTIFIER): | http://dx.doi.org/10.1063/1.1657800 |
| Date Other: | Tue, 28 Sep 2010 23:09 -0500 |
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