2 PRELIMINARY OUTLINE 



geologic facts and principles to mining. Other similar subdivisions 

 might be mentioned. 



Dominant processes. Three sets of processes, still in operation 

 on the surface of the earth, have made much of the record on which 

 the science is based. These processes have been designated dias- 

 trophism, vulcanism (volcanism) , and gradation. Diastrophism 

 includes all movements of the outer parts of the lithosphere, whether 

 slow or rapid, gentle or violent, slight or extensive. Many parts 

 of the land, especially along coasts, are known to be sinking slowly 

 relative to the sea-level, while other parts are known to be rising. 

 The fact that sediments originally deposited beneath the sea now 

 exist in some places at great elevations, together with the fact that 

 certain areas which were once land are now beneath the sea, proves 

 that similar changes have taken place in the past. Earthquakes 

 are another illustration of diastrophism. Vulcanism includes all 

 processes concerned with the movements of lava and other volcanic 

 products, whether they issue at the surface or not. Vulcanism and 

 diastrophism may be closely associated, for many local movements 

 are associated with volcanic eruptions. Gradation includes all 

 those processes which tend to bring the surface of the lithosphere 

 to a common level. Gradational processes belong to two categories 

 those which level down, degradation, and those which level up, 

 aggradation. The transportation of material from the land, whether 

 by rain, rivers, glaciers, waves, or winds, is degradation, and the 

 deposition of the sediment, whether on the land or in the sea, is 

 aggradation. Degradation affects primarily the higher parts of 

 the lithosphere, and aggradation the lower. 



THE EARTH IN THE SOLAR SYSTEM 



Though supremely important to us, the earth is but one of the 

 minor planets which revolve about the sun. Of the eight planets, 

 four, Jupiter, Saturn, Uranus, and Neptune, are much larger than 

 the earth, while three, Mercury, Venus, and Mars, are smaller. 

 There are hundreds of asteroids, but all together they do not equal 

 the mass of the smallest planet. Jupiter, the largest planet, has 

 more than three hundred times the mass of the earth. The earth's 

 position is in no sense distinguished, for it is neither the outermost 

 nor the innermost, nor even the middle planet. In the inner group 

 of four to which it belongs, it is the largest. Its average distance 



