Palæomagnetic evidence relevant to a change in the earth's radius

INTEREST in the hypothesis that the Earth's radius has increased during geological history has been renewed in recent years because of several sets of independent observations and interpretations. From studies of the deformation of mountain ranges and the distribution of faults and oceans, Carey¹ proposes an increase in the Earth's area of 45 per cent since the Palæozoic era. Heezen² similarly interprets submarine topography as indicating that the oceans may be immense rift valleys formed by a pulling apart of the continents as the Earth expanded. Using a different approach, Egyed^3,4 infers a rate of increase of the Earth's radius of 0.4–0.8 mm. per year. This calculation is based on a decrease in the total amount of continental area covered by oceans during the past 400 million years, as determined palæographically. Egyed⁴ has also pointed out the desirability of using palæomagnetic data to test this hypothesis.