280 GEOLOGICAL HISTORY OF LAKE LAHONTAK 



The large group of hot springs near Ward's ranch, on the western 

 border of the Bhick Rock Desert, and the group at the east end of Granite 

 Mountain, are both on hnes of recent displacement. 



The fault that crosses the western border of Smoke Creek Desert differs 

 from most others in the Lahontan basin in the fact that it traverses the 

 valley at a considerable distance from the mountains. Its course is marked 

 by numerous tliermal springs, and by a low scarp which at times becomes 

 too indistinct to be easily traced. There is but little question that this line 

 of displacement is a continuation of the fault to be seen at Granite Mountain, 

 which apparently comes to view again along the borders of the Black Rock 

 Desert farther northward. The connection between these various frag- 

 mental fault lines has not been traced, and we have represented on Plate 

 XLIV only such portions as have actually been observed. The course of 

 this fault across the southern portion of Smoke Creek Desert is indicated 

 by a low and somewhat rounded scarp with a nearly east and west strike. 

 The springs along the fracture irrigate the desert sufficiently to admit of 

 the growtli of grasses and desert shrubs which mark its course by a line of 

 verdure through the absolute waste. Farther northward, in the neiglibor- 

 hood of Sheep Head Spring, the fault changes its course and becomes nearly 

 north and south in its trend; farther northward, still, it bends more to the 

 eastward, and, finally, near Round Hole Spring it has an approximately 

 east and west strike. Its course is thus nearly crescent-shaped, but it has 

 many more irregularities than we are able to represent on the accompany- 

 ing map. On the line of this fault near Buffalo Springs there are a number 

 of tufa piles rising abruptly from the desert to a height of thirty or forty 

 feet, which exhibit the three varieties of tufa that are characteristic of the 

 Lahontan calcareous precipitates. It is evident that the nuclei of these 

 deposits were formed by subaqueous springs, as described in a previous 

 chapter, thus showing that the fracture along which they are situated must 

 have existed during the time the desert was occupied by the ancient lake. 

 In a few instances the tufa piles situated immediately above the line of 

 fracture have been split from base to summit by a recent orographic move- 

 ment, and are now parted by vertical fissures two or three feet wide, into 



