THE STRUCTURE OF THE EARTH 



267 



the highlands, producing a strong line of demarcation (Fig. 265). 

 Such a topographic form is called a fault-line scarp or cliff. 



Sometimes the topography of a region is determined largely by 

 faulting, resulting in steplike hills or mountains. This is well shown 

 in a portion of Oregon (Fig. 266), in the Great Basin region of 



Fig. 265. — Fault in the Scottish Highlands. The strata on the right are 

 weaker than those on the left. 



Utah (p. 354), the Colorado Plateau, and the Connecticut valley 

 of Massachusetts and Connecticut. In central Sweden the criss- 

 cross valleys and lakes of angular and zigzag outline are, either 

 directly or indirectly, due to the faulting of rhomboidal-shaped blocks. 

 The greatest example of faulting now apparent in the topography of 

 the continents is the Great Rift valley of east Africa, which consists 



Fig. 266. — Diagram of a mountain formed by faulting. The slope of the surface of 

 the original block is shown in outline. (Modified after Davis.) 



of a series of grabens (p. 263) in the bottoms of which lakes (Albert, 

 Tanganyika, etc.) are aligned. The magnitude of the displacement 

 is indicated by the depth of Lake Tanganyika, which is nearly 4190 

 feet, the bottom of the lake lying 1600 feet below sea level. This 

 great rift extends from Abyssinia southward for some 1500 miles. 

 In the Adirondacks of New York the " latticed drainage " is to a 



