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Science 22 January 1971:
Vol. 171. no. 3968, pp. 248 - 254
DOI: 10.1126/science.171.3968.248
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Articles

Pacific Geomagnetic Secular Variation

Richard R. Doell 1 and Allan Cox 2

1 U.S. Geological Survey, Menlo Park, California
2 Stanford University, Stanford, California

We have considered several different types of records of long-period geomagnetic secular variation: direct measurements made in geomagnetic observatories; paleomagnetic measurements on Hawaiian lava flows with accurately known ages in the interval 0 to 200 years; paleomagentic measurements on Hawaiian lava flows with loosely determined ages within the interval 200 to 10,000 years ago; and worldwide paleomagnetic measurements of the average geomagnetic angular dispersion recorded in lava flows that formed during the past 0.7 million years. All these magnetic records indicate that, during this time, the nondipole component of the earth's field was lower in the central Pacific than elsewhere, as it is today. This, in turn, indicates that there is some type of inhomogeneity in the lower mantle which is coupled to the earth's core in such a way as to suppress the generation of the nondipole field beneath the central Pacific. With the present incomplete state of knowledge about the processes that give rise to the earth's field, it is uncertain whether undulations in the core-mantle interface or lateral variations in the composition and physical state of the lower mantle are ultimately responsible for the pattern of secular variation seen at the earth's surface.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Earthquake Waves and the Geomagnetic Dynamo.
D. J. Mullan and D. J. Mullan (1973)
Science 181, 553-554
   Abstract »    PDF »
Overtones of Free Oscillations and the Structure of the Earth's Interior.
A. M. Dziewonski and A. M. Dziewonski (1971)
Science 172, 1336-1338
   Abstract »    PDF »


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Science. ISSN 0036-8075 (print), 1095-9203 (online)