1 8 PHILIPPINE AGRICULTURE 



the rocks of the earth, running water also is very active. 

 In cold countries, ice has helped to do this work. 



As is true of walls, some parts of rocks are softer than 

 others, and disintegrate more quickly. Most of the hills 



FIG. 20. Rocks standing out of the sea on the coast of Northern California 



and mountains in the world are the hard spots which 

 have been left, while the softer places around them have 

 worn away. 



KINDS OF SOIL, BY ORIGIN 



Residual Soil and Loess. While the soil was forming 

 from the rocks, some of it was carried away, and some 

 remained at or near the places where it was formed. 

 The latter kind is called residual soil. Some fine soils 

 are so light that the wind can carry them as dust. Soil 

 formed by the settling, or deposition, of fine particles 

 from the air is called loess ; it is usually a very compact 

 soil, because it is made up entirely of fine particles. 

 Dust blown into the air by volcanoes sometimes settles 

 as loess. 



