THE WORLD IN THE MAKING 27 



poured upon the surface only to evaporate promptly, it was so 

 hot. Gradually the surface cooled sufficiently so water could 

 remain. Then the little drops of water congregated in the 

 spaces between the rocks in the upper zone. Gradually these 

 cracks were filled with water and the water overflowed and 

 formed little pools. The pools grew into lakes, and the lakes 

 joined each other and formed oceans. 



The torrential rains washed the rock not covered with water 

 and formed rivers that carried the sediment down and deposited 

 it on the rocks under the oceans. This continued long ages. 

 In this way the ocean floors had the weight of the waters upon 

 them and the added weight of the deposited material. This 

 made them sink, deepening the ocean basins and pushing up the 

 land masses, making the continental platforms higher. 



Now, no sooner were the continental areas raised above the 

 ocean level than all the agencies of erosion were turned loose 

 upon them. The waves beat upon the land, the rain pounded 

 it, the brooks and rivers furrowed it, underground waters honey- 

 combed it, in time snowfields thrust out huge ice sheets to grind 

 down the hills and deepen the valleys, frost shattered the rock 

 cliffs, the gases of the air united with the rocks to alter them into 

 soft materials easily eroded, earthquakes rent the land, the 

 sand-laden winds, the chemical action of organisms growing on 

 the rocks — these all aided in the rock disintegration and soil 

 formation and prepared for the transportation of materials by 

 these same agencies to lower levels and finally to the lakes and 

 seas. 



This process of transportation was as incessant as erosion. 

 Ponds and lakes constantly filled up with the wash from the 

 uplands. Rivers carried immense loads of sediment into the 

 oceans. The United States Geological Survey estimates that 

 the material washed from the surface of this country and carried 

 off by the rivers annually amounts to over one-quarter billion 

 tons. And so the material that was originally rock and had 

 been eroded, transported, and deposited began to fonn rock 



