GEOGRAPHY, TOPOGRAPHY, AND GENERAL GEOLOGY. 
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mapped. The maximum vertical displacement known is 2,000 feet; 
the horizontal displacement is unknown. Hinge faults, the displace- 
ment at one end of which is opposite to that at the other, were found 
locally in the lava area. It is probable that many of the faults with 
a displacement parallel to the dip of the beds have not been mapped 
because not detected. Allowing for a considerable unknown hori- 
zontal component of displacement, there remains a probable domi- 
nance of vertical movement sufficient to indicate that the net result 
Fig. 3.— Plat of faults and iron-ore veins in the Iron Springs district. Solid lines show faults; dotted 
lines, iron-ore veins; and solid and dotted lines, faults and iron-ore vei as. 
of the faulting has been the extension of the area; in other words, the 
faults are primarily tension phenomena. 
Conspicuous in the andesite are fissures, some of them filled with 
ore, which curve, taper, branch, and parallel themselves in such a 
manner as to suggest that they are stretch fractures. In the Three 
Peaks andesite area there is a conspicuous parallel fracturing spaced 
at intervals of a fraction of an inch to a number of feet. In the 
neighborhood of ore veins they have the same trend as the veins, 
