AGENTS OF EROSION 



183 



References : 



1. 1205:56-60. 



2. 1304:51-54. 



3. 1304:66-68. 



4. 1601:15-18. 



a. 1201:23-26. 



b. 1203:108-110. 



c. 1301:257-260. 



d. 1302:57-67. 



e. 1303:245-249. 

 /. 1303 : 25&-261. 

 g. 1305 : 181. 



h. 1309:75. 

 i. 1310:85-91. 



Transportation and Erosion by Streams. 



The Load of Rivers. 



Alluvial Fans and Filling of Valleys. 



The Work of Water. 



How Erosion Exposes the Rocks to our 



View. 



Rivers and the Making of New Land. 

 Erosion of the Land. 

 Erosion. 

 Work of Rivers. 

 Development of Valleys. 

 Weathering and Erosion Defined. 

 Erosion Denned. 

 Erosion and its Effects. 



130. AGENTS OF EROSION , 



Next to rain and rivers, the wind and the ocean waves are 

 the most important agents of erosion. When the air moves 

 with a certain rapidity, it picks up sand and small pebbles 

 and hurls them against rocks and mountains, wearing them 

 away. We may consider that the wind actually becomes a 

 sand blast, each particle of sand and pebble becoming a sort of 

 chisel, which cuts off a grain here and a grain there from the 

 mountain side; but owing to the countless number of grains 

 of sand, the work accomplished is sometimes very great. In 

 sandy districts, telegraph poles and fence posts have been cut 

 through by the action of the blowing sand. 



There is another form of water erosion besides those men- 

 tioned which has a limited zone in which to work. This is the 

 wear of the waves upon the beaches and cliffs which form the 

 shore of the ocean. We have records in some instances where 

 waves have removed large areas of land. On the other hand, 



