Soils and Soil Management 



53 



being slowly but surely converted into soil. The large 

 boulders break and fall from the cliffs, and by the weath- 

 ing of the rains, frosts and other agencies, they are 

 worn away. The finer particles are washed down the 

 hillsides into the valley below, forming the rich valley 

 soil. Soils formed in this way by the deposit of the 

 sediment from running water are called sedimentary 

 soils. In some cases the rocks break up and are not 



Fig. 33. Soil formation. Rain, frost and plants all assist in changing the moun- 

 tains of rock into soil. After Hill. United States Geological Survey. 



