Geologists up the Pole?

On Thursday, March 23, the Math, and Physics Society gathered to hear New Zealand's prominent Dr. F. F. Evison talk on "The Meaning of Rock Magnetism." Dr. Evison outlined the background of the subject, giving at fair length the growth of the different theories to explain the apparent shifting of the magnetic pole with respect to the rocks of a sample. He showed that, although most of the sampling has been carried out in Western Europe, there has been a small amount of data collected to give an overall picture of the magnetic field direction throughout history. The theories which have evolved to account for this phenomenon have included: Polar wandering, continental "drifting" and continental rotation. This collection can, as he said, account for any possible variation but as a physicist the speaker said he could not accept that whole continents just floated about all over the globe without any apparent force to move them. It was at this final stage of the evening that Dr. Evison dropped his geophysical " bombshell." He unfortunately, had not left time to develop the full extent of his astounding theory but briefly sketched it for the meeting.

He has developed the novel idea of replacing the wholesale juggling of continents under forces unknown with the gradual "plastic" flow of the continent rocks under the well known force of gravity. This apparent heresy certainly rocked the geologists present.

It was shown that allowing for a gradual spreading of the high areas of land under the effects of gravity and the building up of new areas by volcanic activity, and, sedimentation and holding, gave a much closer approximation to the experimentally observable facts. A question asked by our geologist's representative on the reason for so many intact fossils being collected instead of only sheared fragments was quickly and characteristically answered by Dr. Evison on both statistical and physical grounds. He said that geologists had told him that most of the fossils found by them were sheared and regarded as useless. However, he added, it was not unlikely that owing to the very gradual "flow" of the rock, "bubbles" of fossil bed would be left intact.

This talk showed that in Dr. Evison the D.S.I.R. Geophysics division, and indeed all New Zealand, have a lively, clear thinking physicist. It is to be hoped that this talk may spur some of our rising generation of physicists to not regard Nuclear Physics as the only field of interest for their talents.

The evening ended with supper and a lengthy although not very heated discussion in the Stage I laboratory.