CHARACTERISTICS OF RECENT FAULTS. 283 



and meets with apparent opposition in the case of the fault along the 

 western border of Walker Lake. In this instance a depression of the 

 thrown block is indicated by the deepening of the waters of the lake as one 

 approaches the line of displacement As pointed out by Mr. Gilbert, Great 

 Salt Lake has probably been shifted to the eastward of its noi'mal position 

 by orographic movement, which we may consider, at least in part, as the 

 result of a movement of the great Wasatch fault; thus indicating that the 

 thrown side of the displacement was depressed. 



By way of a summary of this chapter we may state that the recent 

 faults of the Great Basin have the following characteristics: 



They are irregular and angular in their course, in reference to both 

 vertical and horizontal planes. 



They occur most commonly on the steeper side of the basin ranges, 

 and, so far as known, invariably hade toward the valley, i. e., the valleys 

 occupy the thrown sides of the displacements. 



Their scarps occur in alluvium and in lacustral beds, and cut the embank- 

 ments and terraces of Quaternary lakes; many times they present fresh 

 slopes of earth and gravel that are unclothed by vegetation, and but little 

 affected by erosion. Occasionally they cross stream-beds and cause rapids; 

 as is the case where the Wasatch fault crosses American Fork, Utah. 



At hundreds of localities thermal springs come to the surface along the 

 lines of fracture. 



In the majority of instances the recent movement has taken place 

 along ancient lines of displacement; the post-Quaternary fault in such 

 cases is but a small fraction of the entire disturbance. 



