A LIVING FROM THE LAND 



and breaking up of the rock as it becomes heated 

 and cooled under atmospheric influence. 



A great deal of the soil surface in many 

 sections of the country is the result of glacial 

 action. These glaciers not only eroded the sur- 

 face, thereby creating millions of rock particles, 

 but they also carried large deposits of the rock 

 particles to more distant areas and deposited 

 them over a subsoil that may be totally dif- 

 ferent in character from the surface soil thus 

 deposited. 



How Tillable Soil Is Made. The action of 

 plants themselves has a great effect in adding 

 to our supply of tillable soil. Seeds of plants or 

 seeds of trees become established in some slightly 

 weathered rock areas and begin to grow. The 

 roots penetrate wherever there is any loose 

 soil, and partly by their pressure and partly 

 through the acidity accompanying decomposing 

 plant tissue, complete a further breaking down 

 of the rock. There is a continuous process of 

 destruction of rocks and leveling off of mountains 

 and hills to fill the valleys below. 



Many groups of deep-rooted plants tend to 

 increase the depth of the surface soil by growth 

 of the roots in the subsoil and by creating 

 therein a condition approaching that which 

 already exists on the surface. The action of 

 earth worms and similar forms of life in bringing 



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