G. K. Gilbert—Earthquakes of the Great Basin. 51 
sloping mass called the foot-slope, or colloquially the “ bench.” 
When an earthquake occurs, a part of the foot-slope goes up 
with the mountain, and another part goes down (relatively) 
with the valley. It is thus divided, and a little cliff marks the 
line of division. A man ascending the foot-slope encounters 
here an abrupt hill, and finds the original grade resume 
beyond. This little cliff is, in geologic parlance, a “ fault- 
scarp,” and the earth fracture which has permitted the moun- 
tain to be uplifted is a “fault.” In the course of time the 
same slow process of erosion and deposition which originally 
formed the foot-slope restores its shape and obliterates the fault- 
scarp. When a mountain ceases to grow, its fault-scarp soon 
disappears ; and conversely, when we find a fault-searp at the 
ase of a mountain, we are assured that the uplifting force has 
not ceased to act. Fault-scarps have now been found at the 
bases of so many ranges of the Great Basin, that it is safe to 
Say that the subterranean forces are generally active in this 
region, and this is especially true of all the large mountain 
masses. The Wasatch is a conspicuous example, and residents 
of this city need not go far for ocular demonstration. A fault- 
scarp, thirty or forty feet high, divides the powder houses north 
of the Hot Spring, so that some of them stand above and some 
elow it, and considerable grading was necessary to lead the 
road to the upper magazines. With one exception, all the 
lime kilns between the powder houses and the Warm Springs 
are built in the face of the fault-scarp, the lime rock being con- 
veniently delivered to the kilns from the upper level, and the 
lime as conveniently drawn out at the lower level. At the 
mouth of Little Cottonwood Cafion, a smelter has been built 
on the edge of the upper bench for the convenience of dump- 
ing its slag over the fault-scarp. At the mouth of Spanish 
Fork Cafion, the D. & R. G. Railroad encounters the scarp, and 
the engineers have started an embankment a long way back to 
climb it. Similar features may be seen, with rare intervals, all 
along the mountain base from Nephi to Willard. 
he fault-scarps of the Wasatch follow the western base. 
Those of the Sierra Nevada follow the eastern base; and it 
number of feet below their previous positions, and one tract, 
Several thousand acres in extent, was not only lowered, but 
carried bodily about fifteen feet northward. The ground was — 
cracked in various directions, and several springs permaneatly ae 
isappeared. All houses of adobe or stone in the immediate 
