AND ITS INHABITANTS 75 



see the periodic rejuvenation of the lands and the renewal of 

 active erosion. During these times of crustal unrest and 

 subsequent internal readjustment the molten portions deep 

 down in the lithosphere are forced to rise as great hot tongues 

 into the cores of the mountain ranges, and in many places they 

 break through and give rise to active volcanoes. Beneath lie 

 great and highly heated masses that subsequently cool into 

 granitic rocks, and when long afterward the mountains are 

 worn away we discern among their roots these cores of granite. 

 However, during all the time of crustal rising and readjust- 

 ments the volcanoes are more or less active, spewing violently 

 or quietly into the atmosphere tremendous volumes of rocks 

 blown into volcanic ashes and of lavas, and great quantities of 

 gases that increase the volume of the atmosphere, and much 

 juvenile water Is added by them and the thermal springs to the 

 vadose water of the hydrosphere. Even though the litho- 

 sphere absorbs much vadose water through soaking and min- 

 eralization, the oceans are yet constantly growing in volume 

 through this accession of juvenile water. In the same way, 

 even though vast quantities of carbon are taken out of the 

 atmosphere by organic agency and buried in the rocks, there 

 to be transformed into natural gases, petroleum, asphalt, peat, 

 and coal, the air Is periodically resupplled by the volcanoes 

 and by the hot-water springs. 



Periodic spreading of the oceans. So far we have been 

 describing the alterations that take place In the dry land; let 

 us now turn to the realms of Neptune and note briefly the 

 areal fluctuations of the oceanic waters during the latter half 

 of geologic time. The geography of the earlier times we have 

 not as yet deciphered and therefore cannot relate the move- 

 ments of the oceans. It has been stated that when the earth 

 shrinks, the lands rise In relation to the strand-line, and that 

 this is especially true at the times of major crustal alterations. 

 It is now definitely known that at the close of all the eras the 



