paleomagnetism

Polar wandering curves for the various continents through geological time based on paleomagnetic data. The numbers refer to: 1. Precambrian; 2. Cambrian; 3. Ordovician; 4. Silurian; 5. Devonian; 6. Carboniferous; 7. Permian; 8. Triassic; 9. Jurassic; 10. Cretaceous; 11. Tertiary; 12. Quaternary. Since these curves, which describe the apparent positions of the north magnetic pole as determined from different continents, are not only colinear but also show remarkable differences of form, the only apparent explanation of polar wandering would seem to be that the continents have moved relative to each other

The study of past changes in the Earth's magnetic field (see geomagnetic field) by examination of rocks containing certain iron-bearing minerals (e.g., hematite, magnetite). Reversals of the field and movements of the magnetic poles can be charted and information on continental drift may be obtained. See also seafloor-spreading.

Related category

• GEOLOGY AND PLANETARY SCIENCE

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