Some investigations of isostasy and Earth's contraction

Abstract

1. Seismic and gravity investigations have revealed that the Earth's crust is quite different on continents and under oceans; therefore the continents and the ocean basins cannot be upheavals and subsidences due to the contraction of the Earth. So the contraction hypothesis fails in the explanation of major features of the globe. Vertical movements play the leading part in the evolution of the Earth's crust and they change sign in time. It is inexplicable from the standpoint of Earth's contractions. Continents grow laterally, evidently new portion of continental crust is being formed. No explanation for this can be given by contraction hypothesis. 2. Assuming contraction hypothesis the diminution of the Earth's surface from geological data is at least 5 per cent during each tectonic cycle. As at least 15 cycles have passed since the Earth's formation the total shortening would be half of the whole surface, which is impossible. 3. Every great circle of the Earth is to shorten equally. Nevertheless, as we see from the globe, the shortening would be very different, if it were. E. g. the circle consisting of meridians 15° W and 165° E has no indication of significant shortening, while along the circle 90° W, 90° E there was a great shrinkage (mainly on account of the mountain buildings in Asia). In general, there are too few great structures stretching latitudely on the globe. It is inconsistent with the idea of the Earth's uniform shrinkage. 4. The contraction hypothesis supposes that folded mountains are due to the squeezing a geosyncline (orogen) between two platforms