182 GEOLOGY OF THE HIGH PLATEAUS. 



summit of the crest are still discernible, though now they lie at least 3,000 

 feet below them. 



Immediately south of Midget's Crest lies Dog Valley — a pleasant 

 moderately diversified platform — with an absolute altitude of about 7,500 

 feet or 1,500 feet above the Sevier at Circle Valley. It is a part of the 

 last-mentioned focus of eruptions of the second or middle epoch, but erosion 

 has leveled down most of the ancient irregularities, and left it a field of 

 rolling lulls, well covered with soil, loam, and sharp gravels. Its real history 

 might not have been suspected, were it not for the vast floods of lava which 

 spread out from it in all directions for many miles, growing thinner and 

 broader as they recede. 



Southwest of Midget's Crest the altitude of the plateau gradually 

 diminishes until its summit at last is lost in the next region. The fault 

 which originated the escarpment of the plateau suddenly becomes a mono- 

 clinal which dies out in the space of about 6 miles. This monoclinal is 

 composed of conglomerate of unknown thickness, but not less than 1,500 

 feet in the vicinity of the flexure. It turns up at an angle of 28° to 30° 

 against the diminishing wall of the plateau, but soon straightens out towards 

 the south and decreases rapidly in thickness. It is composed of basaltic 

 (doleritic) materials chiefly, quite similar to, and perhaps identical in part 

 with, the remnants of that kind of rock forming the extreme summits of the 

 salients on Midget's Crest. 



The western base of the Tushar I have seen in part only, and have 

 given that part merely a cursory examination. It is possible that there 

 exists a fault of about 1,200 feet along this base with a throw to the west; 

 a continuation of the Hurricane fault, which appears in great force about 

 15 miles south of the southwest slope of the Tushar. But I have not 

 verified the existence of such a fault in this locality, and such an occurrence 

 may not be necessary to explain the features presented, so far as observed- 

 The summit of the table, after maintaining for about 10 miles an easy slope 

 to the west, suddenly increases the descent of the profile to the broad plain 

 below. The surface contour here cuts across the ends of the lava sheets, 

 which are seen to be considerably attenuated when compared with* the 

 huge masses exposed upon the upturned eastern flank of the range. 



