CHAPTER XX. 



CRUSTAL DEFORMATION AS THE CAUSE OF CLIMATIC CHANGES. 



We have been led to the conclusion that among the four chief hypotheses of chmatic 

 change only the solar hypothesis seems competent to explain the pulsations, large and 

 small, which have taken place from the glacial period to the present time. In the case of 

 the greatest of all climatic changes, however, this theory in its tm-n appears to be inade- 

 quate. So far as we can see, no possible change in the sun's radiation, or in volcanic 

 activity, could cause such a complete redistribution of the earth's cUmatic zones as we find in 

 the Permian and other eras. It might cause the zones to be pushed greatly toward or away 

 from the equator, to contract or expand, and to vary considerably in temperature, but it 

 could scarcely cause them to be reversed in such a way as to make the polar regions as warm 

 as the equator. The carbonic acid theory, in spite of ingenious attempts to indicate a 

 possible method to the contrary, also seems to many geologists inadequate to produce any 

 such result, and even the framers of the theory admit that this is the case. They fall back 

 upon the well-established theory of changes in the form and altitude of the lands, and 

 consequent alterations of oceanic and atmospheric circulation. Other students suggest 

 that the pecuharities of Permian times may have been due to a shifting of the earth's axis 

 of rotation, but astronomers and physicists find so many objections to this hypothesis that 

 we can not wisely lay much stress on it. 



Before discussing this matter any fm-ther and suggesting a possible relationship between 

 solar changes and crustal deformation, it will be well to review the climatic history of 

 geological times as a whole. In such a review there is much opportunity for the exercise 

 of personal judgment. In this respect it is harder to deal with geological times than with 

 the historic period wherein we can rely upon actual records, such as those of the growth 

 of trees. In order to obtain as unbiased a statement of the facts as possible, 1 have asked 

 Professor Charles Schuchert to contribute a discussion of geological cHmates. This dis- 

 cussion is probably the fullest and most authoritative that has yet appeared. It is printed 

 as the concluding portion of this volume. Professor Schuchert wrote his paper without 

 regard to the theories discussed in this book, and without definite knowledge of them. 

 His statements may be taken as representing the mature conclusions of the most advanced 

 students of geology and paleontology. Where matters are doubtful, he has clearly stated 

 the doubt, but so far as our present problem is concerned the points wherein geologists 

 disagree are not of vital importance. The student who would understand the matter 

 thoroughly is referred to Professor Schuchert's paper. In the following paragraphs I shall 

 recapitulate some of his chief conclusions, and shall see how they bear on those already 

 reached in this volume. 



The study of paleometeorology, as set forth by Professor Schuchert, leads to the 

 conclusion that the earth has passed through a considerable number of great climatic 

 changes, either glacial periods or other periods marked by a pronounced decrease in temper- 

 ature or increase in aridity. The best-known is of course the Pleistocene glacial period. 

 Equally important, though more remote and less well known in detail, is the glacial period 

 of early Permic time. Both glaciations were world-wide in their effect, and were char- 

 acterized by a change in temperature sufficient to occasion vast accumulations of snow 

 and ice, not only in polar regions and at high altitudes, but even more markedly at low 

 levels in middle or almost equatorial latitudes where the glaciation in many places reached 



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