Continental drift is of great importance to glaciologists as it affords the only credible explanation of the Permo-Carboniferous glaciation of the now widely separated Southern Hemisphere continents. Wegener’s theory was shelved on geophysical grounds and the appearance of this stimulating book is ample proof that the geophysicists have repented. It consists of easily readable contributions by a dozen experts from quite widely different geophysical fields. In all of them, however, movements in the crust and mantle, only slightly less spectacular than those involved in continental drift, are somewhere postulated.
Recent interest in continental drift has been revived by palaeomagnetic studies which are reviewed in the first chapter by the editor who is himself a vigorous worker in this field. The palaeomagnetic data are reconciled with the palaeoclimatic data in the second chapter. The next three chapters discuss large horizontal movements in the Earth’s crust as revealed by earthquake and magnetic studies. That the search for a mechanism usually involves a consideration of thermal convection in the Earth’s mantle is largely due to the work of Vening Mcinesz who has contributed a most illuminating chapter, which is followed by one in which the theory of convection in spherical shells is developed and applied to the Earth’s mantle. Convection is also involved in some of the mountain-building hypotheses which are fully discussed (and all found wanting) by Chadwick. The two-thirds of the Earth under water are not ignored. The longest chapter deals with the deep sea-floor in which Heezen discusses the drift hypotheses. Dietz is given the succeeding chapter to present his “sea-floor spreading“mechanism. Gaskell, in the final chapter, concludes that the differences between the Pacific and Atlantic Ocean floors may well be due to drift. The book concludes with a chapter devoted to Wegener.
No specific pronouncements about continental drift are made in this book, the aim of which the editor says has been to stimulate. By taking us to the frontier in so many fields, one feels it will be stimulating for some years to come.
