Several complex polar and continental movement hypotheses have been proposed to explain paleomagnetic data. Each hypothesis: (1) contradicts some fundamental geological-geophysical data, (2) fails to explain the many separated polar movement curves, and (3) assumes that the dynamo theory of the earth’s magnetic field is essentially correct. The last involves two corollary assumptions: (a) that the geomagnetic and rotational poles always have coincided approximately and (b) that the dynamo theory applies to all geological history. “Contouring” of the geomagnetic polar positions which have been determined from rocks of different ages in many areas suggests strongly that the present axial dipole field has developed since latest Precambrian time, and that this dipole field did not become dominant before late Mesozoic time. This would imply that the dynamo theory is not applicable to pre-late Mesozoic time. If this conclusion is correct, complex polar and continental movement hypotheses may be unnecessary. A new earth model then would be needed to explain: (1) the behavior of the earth’s magnetic field prior to late Mesozoic time and (2) the mechanism of growth of the present axial dipole field.

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