CHAPTER XII 



THE CRUST OF THE EARTH 



283. Lithospheric Changes. In the Abysmal Area 

 the hydrosphere protects the solid rock beneath, by the 

 extremely slow formation of a covering of red clay or ooze. 

 In the Transitional Area, where the hydrosphere is stirred 

 more forcibly by solar energy, the formation of deposits is 

 accompanied by the wearing away of rocks. All our know- 

 ledge of the substance and structure of the lithosphere is 

 obtained by studying the processes of change going on in 

 the Continental Area, which alone is open to our inspection. 

 It is subject to much greater changes than the other areas on 

 account of the strong action of solar energy, which through 

 various agents is always crumbling down the heights and 

 carrying the resulting detritus to the sea-margin. In the 

 course of time this action, termed erosion, would, if not 

 counterbalanced, reduce the whole Continental Area below 

 sea-level. 



284. Elevation and Subsidence. The attention of 

 tourists along the steep coasts of Norway and Scotland is 

 often attracted by lines of horizontal terraces running par- 

 allel to each other at various heights above the shore. These 

 when examined are found to be shelves or notches cut out 

 of hard rock or soft ground, sometimes covered with pebbles 

 and sand often containing sea-shells. Behind the terrace 

 the cliffs are sometimes perforated by caves, which show 

 every mark of having been excavated by wave action ( 266). 

 The terraces are in fact raised beaches, and their position 



