THE SAN ANDREAS RIFT AS A GEOMORPHIC FEATURE. 41 
its upper edge, are two parallel lines of faulting, probably made at a later date than 
the bluff itself. A small lake occupies a hollow in one. ‘The slopes of one of these V- 
shaped depressions are quite steep, pointing to a comparatively recent origin. 
The people living along the Rift for 150 miles southeastward from the Cholame Valley 
tell wonderful stories of openings made in the earth by the earthquake of 1857. The 
first settler in Cholame Valley was erecting his cabin at that time, and it was shaken 
down. The surface was changed and springs broke out where there had been none before. 
In 1901 a fissure opened in the road which crosses the branch fault just described. After 
each successive shake it is reported that the fissure opened anew, so that the road had 
to be repaired again in order to be passable. 
Upon the western side of the Cholame Valley, near its southern end, the main Rift 
again exhibits an interesting bluff which cuts off the débris fans of the back-lying hills. 
This bluff faces northeasterly. Where the Rift crosses the creek as it passes out of the 
Cholame Valley, a low escarpment was formed upon the west side which must for a time 
have dammed the creek and given rise to a lake. From the outlet of the Cholame Valley 
the Rift line can be seen as it rises along the low rolling hills, and disappears over their 
tops. It is marked by a distinctly steeper slope facing northwesterly, showing that an 
uplift of 30 to 50 feet took place upon the west side. The region traversed thru the 
Cholame Valley southeast to the Carissa Plain and for some miles beyond, exhibits no 
older formation than the Miocene Tertiary, the effects of older faulting, if such has 
occurred here, being masked by recent deposits. Continuing the examination toward 
the southeast, the writer came upon the Rift at the northern end of the Carissa Plain, 
4 miles northeast of Simmler P.O., and in direct line with its course where last seen. 
Here the width of the broken country is much greater than usual, being nearly a mile. 
A number of lines of displacement can be distinguished; some nearly obliterated, others 
comparatively fresh. This is a region of light rainfall and of gentle, grass-covered slopes, 
presenting just such conditions as would preserve for hundreds of years the effects of 
moderate displacements. 
The Rift zone continues to be traceable along the western base of the Temblor Range, 
finally passing out on to the gently rolling surface of the eastern edge of Carissa Plain. 
Broken and irregular slopes, cut-off ridges, blocked ravines, and hollows which are white 
with alkaline deposits from standing water mark the Rift. Carissa Plain has a length of 
about 30 miles. About halfway the Rift begins to be marked by a low and nearly oblit- 
erated bluff upon its northeastern wall. This is at first little more than a succession of 
ridges or hills cut off on the side next to the level plains. These detached ridges finally 
become connected in a regular line of hills with a steep but deeply dissected slope toward 
the southwest and long gentle slopes toward the northeast. This ridge is clearly a fault 
block, and now separates the southeastern arm of Carissa Plain from Elkhorn Plain. It 
probably originated during some one of the earlier movements along the Rift; in fact, 
it is reasonable to suppose that it is of the same age as other important scarps which mark 
the Rift thruout its whole course, and which came into existence as a result of some 
mighty movement opening the earth for several hundred miles. 
Except for one slight bend, the ridge which we have been describing follows a straight 
course toward the southeast for a distance of nearly 20 miles, finally blending in a much 
larger mountain-like elevation. This has a height of perhaps 500 feet above the sink 
at its southern base. Its deeply dissected front is in line with the front of the ridge 
already described and the two appear to have originated together. The steeper face is 
deeply sculptured into gullies and sharp ridges, while the back slopes off gently toward 
the southern end of Elkhorn Plain. Plainly visible along the steep front of the line of 
hills described are the lesser ridges and hollows produced during the last violent earth- 
quake in this region, probably in 1857. (See plate 214, B, c.) 
