SHAPING THE EARTH — BOWIE 327 



earth's surface must have been increased by approximately fifteen 

 millions of square miles. The solid crust, which at the time of the 

 birth of the moon must have been 30 or 40 miles in thickness, could 

 not have stretched over this increased surface but would have been 

 fractured and torn apart with great gaps between the crustal blocks. 

 It may be that this distortion just prior to the birtli of the moon 

 had more to do with the scattering of the remaining crustal ma- 

 terial over the earth's surface than the actual disruption. 



It is ratlier interesting to look at a globe and note that the two 

 coasts of the Atlantic are so nearly parallel that they remind one 

 of the shores of a great river. Wegener has advanced a theory 

 that Nortli and South America broke away from the rest of the 

 continental masses and moved westward during recent geological 

 times. This is a very interesting theory which has many advo- 

 cates and also many opponents. I am rather inclined to think that 

 there are difficulties in the Wegener hj^pothesis which are very hard 

 to explain away. It seems to me that tlie Fisher idea of the birth 

 of the moon gives us a rather logical explanation of the creation 

 of oceans and continents, and the strongest point of this theory is 

 that it does no violence to isostasy. 



It is certain that the earth's surface was irregular at the begin- 

 ning of the sedimentary age, for without irregularities, such as we 

 now have, the water of the oceans would have covered the whole 

 earth's surface to a depth of approximately 9,000 feet if the amount 

 of water was the same as now. With all of the land area covered 

 by water, there could have been no erosion and sedimentation, such 

 as we have had for a period of approximately one and one-half 

 billions of years. 



KNOWN FACTS ABOUT THE EARTH 



The earth should be treated like any material structure which 

 comes under our observation for explanation or analysis. No one, 

 of course, can give us the true explanation of how the earth came 

 into being or state accurately what has been going on to change its 

 surface configuration. But we have now at hand a number of facts 

 which should enable us to arrive at some logical conclusions. We 

 know, of course, the earth's shape and size, the portions of its sur- 

 face covered by land and water, its average density, and the density 

 of its surface material. We also know that the temperature increases 

 witli deptli. We know that there are many earthquakes occurring 

 annually and that there is no area which is entirely free from them. 

 Most of the quakes are extremely slight, but we are reasonably cer- 

 tain that, with few exceptions, they result from breaking rock and, 

 therefore, there must be forces within the earth large enough to cause 

 such breaking. 



