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ROCKS AND SOIL 



The Delaware Water Gap. Are these mountains old or young? How do you 



know? 



northern United States as far as the Missouri and Ohio 

 rivers. The tremendous weight of ice, thousands of 

 feet deep, scoured and broke off projecting hilltops and 

 mountain peaks. The stone fragments moving along 

 under the ice were efficient cutting tools for grinding 

 other rocks underneath. At the front of the ice sheet 

 streams of water poured out, carrying dirt and rocks, 

 which were deposited in layers, just as material transported 

 by our rivers is being deposited today. 



How We Can Use Our Knowledge about Erosion. If you 

 were fortunate enough to take a trip across our continent, 

 you would be able to see some of the results of the various 

 agents and to interpret them as you went along. In the 

 far West you would pass through deep, rocky canyons 

 having steep, jagged sides. We recognize these and the 

 sharp rugged mountains of the West as the results of 

 quite recent erosion, as geological time goes. We would 

 see great deserts of wind-blown earth and sand and many 

 groups of fantastic rocks carved and etched by the 



