428 W. M. Davis— Topographic Development of the 



graphic blocks. These have been tilted so as to form small 

 but extremely rugged mountain ranges, often from fifty to a 

 hundred miles in length, with a width of but a few miles." — 

 The fractures by which the blocks are separated "are of a 

 comparatively recent date, and present bold scarps, that are 

 frequently but slightly scarred by erosion, while the most 

 recent examples of all were unquestionably formed within the 

 past few years, and are yet unclothed by vegetation." . . . "The 

 exhibition of fault-scarps, tilted blocks, and sunken areas, to 

 be seen at the southern end of the Warner Lakes, is the most 

 interesting of its kind that it has ever been our privilege to 

 examine. In this narrow zone, the orographic blocks of dark 

 volcanic rock are literally tossed about like the cakes of ice 

 in an ice-floe ; their upturned edges forming bold palisades 

 that render the region all but impassable." ..." These fault- 

 scarps rise in sheer precipices that overshadow the Warner 

 Lakes throughout their entire extent. Toward the northern 

 end of the valley the great fault-scarp forming its eastern wall 

 sends off a number of branches, at quite regular intervals, with 

 a general northwest trend. The blocks thus separated pass 

 under the lake beds that floor the valley, and appear again on 

 its western border, where they form cliffs of considerable 

 height." ..." It is between the high walls enclosing the 

 southern portion of the valley that the greatest confusion of 

 the minor blocks is to be seen. Many of these fragments 

 measure a mile or so on their edges and are tilted in various 

 directions, leaving narrow rugged valleys between their up- 

 turned margins. The diverse tilting and the numerous fault- 

 scarps that rise without system into naked precipices combine 

 to make this a region of the roughest and wildest description." 

 (Fourth Ann. Eeport IT. S. G. S., 443, 445, 446.) 



It is apparent from these extracts and from others that could 

 be quoted that while southern Oregon has a more complicated 

 structure than that of the Connecticut Trias, it nevertheless 

 serves admirably as a picture of the early stages of the latter, 

 when its faults were still growing : except in the matter of 

 diverse displacement and in the amount of erosion suffered, the 

 description of these long narrow blocks might apply to those 

 of the Connecticut valley. 



The blocks in Idaho have been dislocated so rapidly and so 

 recently that they preserve their constructional topography 

 with insignificant alteration, and in this they are the best 

 examples of any region yet described. Nowhere else can we 

 find so good an illustration of a mountain system in its infancy 

 — almost in its birth. A similar constructional topography 

 probably once existed in Connecticut ; but it has long since 

 disappeared. The upper surface of the Triassic region being 



