Product Synopsis

This historic book may have numerous typos, missing text, images, or index. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. 1922. Not illustrated. Excerpt: ... CHAPTER XVI THE EARTH'S CRUST AND THE SUN A LTHOUGH the problems of this book may lead far / afield, they ultimately bring us back to the earth j and to the present. Several times in the preceding pages there has been mention of the fact that periods of extreme climatic fluctuations are closely associated with great movements of the earth's crust whereby mountains are uplifted and continents upheaved. In attempting to explain this association the general tendency has been to look largely at the past instead of the present. Hence it has been almost impossible to choose among three possibilities, all beset with difficulties. First, the movements of the crust may have caused the climatic fluctuations; second, climatic changes may cause crustal movements; and third, variations in solar activity or in some other outside agency may give rise to both types of terrestrial phenomena. The idea that movements of the earth's crust are the main cause of geological changes of climate is becoming increasingly untenable as the complexity and rapidity of climatic changes become more clear, especially during post-glacial times. It implies that the earth's surface moves up and down with a speed and facility which appear to be out of the question. If volcanic activity be invoked the problem becomes no clearer. Even if volcanic dust should fill the air frequently and completely, neither its presence nor absence would produce such peculiar features as the localization of glaciers, the distribution of loess, and the mild climate of most parts of geological time. Nevertheless, because of the great difficulties presented by the other two possibilities many geologists still hold that directly or indirectly the greater climatic changes have been mainly due to movements of the ea...