SOIL FORMATION NOT A SIMPLE PROCESS 7 



Other Forces of Nature. — These weathering agencies are as- 

 sisted in rock destruction by other forces of nature, such as volcanic 

 eruptions, earthquakes, the force of gravity, etc., and to a greatei? 

 or less degree by plants and animals. Plants in their growth fre- 

 quently crack and split rocks because of root expansion, and hasten 

 rock decay through chemical action caused by certain substances 

 excreted from their roots. Man as a destructive creature has cut 

 down forests and destroyed the natural soil covering of grass and 

 shrubs. The washing away of the soil which follows very often ex- 



FiG. 3. — The •' Dutch Wedding," Monumental Park, Colorado. Sandstone rocks 

 sculptured by the erosive action of water (in past ages) and wind. New International 

 Cyclopedia. 



poses new rock surfaces to the weathering agencies (Fig. 4). Bur- 

 rowing animals also expose fresh rock surfaces, or openings made by 

 them facilitate the entrance of weathering agents to lower levels. 

 Fungi, and even the tiny bacteria lend their aid. Even after plants 

 and animals are dead they contribute further to rock decay, since 

 in their decay acids are formed which hasten the changing of rock 

 and rock particles into soil. 



Soil Formation not a Simple Process. — It is evident that soil 

 formation is not a simple process, but rather complex and slow. It 

 began no doubt as soon as the once gaseous and molten earth passed 



