CHAPTER V 

 THE BEHAVIOR OF RIVERS 



Two Opposing Forces Always at Work 



Throughout the earth two great geologic forces are con- 

 stantly at work, tearing down and building up. Wherever 

 there is land the forces of destruction or tearing down are at 

 work. Correspondingly somewhere building-up processes are 

 going on. Frost and heat, wind, and chemical agencies are all 

 the time at work breaking down the rocks, and the broken 

 particles tend to be carried away by running water. No rocks 

 are so hard that they are not affected by chemical agencies. 

 No rocks are so resistant to the action of wind and the impact 

 of running water that they are not worn and broken and re- 

 duced to particles. Then running water tends to carry the 

 broken fragments down-hill in response to gravity. Thus the 

 continents are being all the time worn down and the rock par- 

 ticles transported to the sea. On the sea bottom ultimately all 

 come to rest. Here the tiny sand grains and muds settle and 

 new sedimentary formations are built up. These tend to 

 become solidified, and new geologic formations are the result. 



Continents and seas are all the time changing. Land areas 

 are depressed and sea bottoms are uplifted. Sediments depos- 

 ited in the seas have become dry land; the muds have become 

 solid rock. Wind, frost and water all set to work again to 

 destroy the rocks, and again carry the particles to the sea. 

 This has been going on throughout all geologic time ever 

 since the land of the primitive continents first appeared above 

 the surface of the primeval ocean. Rivers have been the great 

 agency of transportation. They not only carry away the bits 

 of broken rock, but running water is a powerful agent of de- 



