214 



ROCKS AND SOIL 



forests giving place to fertile farms instead of rocky 



slopes. 



The story of soil making goes back a long, long way 



into the past history of the earth. We must look back 



millions upon millions 

 of years to an earth 

 with no life, no soil, 

 nothing but water 

 and masses of rock. 

 It would be too long 

 a story to tell how 

 all the different kinds 

 of rocks were formed, 

 for soil was made 

 gradually from the 

 rocks. Frost and 

 heat chipped the 

 rocks, winds blew 

 particles against 

 them, glaciers gouged 

 them out and de- 

 posited the ground- 



\\Tigntfierce j. . ,-. 



A mountain stream. Why are the rocks rounded ? U P Sediment in the 



streams formed from 



their melting ice. Streams of water tore their way 

 down mountainsides and ground up particles of rock as 

 they went. All these forces slowly but effectively did 

 their work and helped make the first soil. Then after 

 plants appeared on the earth, their dead bodies decayed 

 and went to help form soil. Thus two kinds of soil 

 could be found : that made from the original rocks 

 and that containing the decayed bodies of plants and 

 animals. 



But under the layers of humus or decayed organic 

 matter and the various layers of loam, clay, or gravel, we 



