46 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 
clear farther north. Two miles southeast of Oak Glen is Pine Bench, a mesa-like remnant 
of gravel having an elevation of about 5,000 feet. At the northern edge of this mesa, 
and upon the line of the fault, there is a regular escarpment facing the higher mountains. 
It is most reasonable to interpret this as indication of the same displacement referred 
to previously. 
To the east of the San Gorgonio River, the topography as shown upon the San Gorgonio 
quadrangle gives little indication of the presence of an important fault-line. However, 
an examination of Potrero Creek shows small transverse canyons and one broad, grassy 
flat with springs upon the line of the fault. In Stubby Canyon and other small canyons 
north of Cabazon Station, the fault is finely shown. Here, as at the point where the Santa 
Ana River issues from the mountains, the older Pleistocene gravels have been faulted 
down against the crystalline rocks. Rapid erosion of both the Pleistocene deposits and 
the crystalline rocks has given rise to steep and precipitous slopes in this section, and 
upon these the fault is clearly shown. The schists and gneisses thru a width of hundreds 
of feet adjoining the fault have been so crusht by pressure and movement that they quickly 
crumble upon exposure. Dark clay marks the plane of movement which inclines to the 
north at an angle of about 80 degrees. Later than the period of main faulting has come 
an elevation of the range as a whole, giving rise to rapid erosion upon both sides of the 
line of fracture. Remnants of gravel mesas and mature topographic forms appear in 
places. A notable example of an area of old topographic features now being destroyed 
by the modern canyons is shown to the west of Stubby Canyon and 1,000 feet above it. 
There are traces here and there of recent displacements along the Rift. These are 
of the nature of little sags without outlets and low ridges or escarpments not easily 
explainable as a product of ordinary erosion. These may have arisen as the product of 
landslides, but the landslides themselves are doubtless related to fault movements. The 
great débris fans built up along the north side of San Gorgonio Pass indicate rapid 
removal of a vast amount of rock material from the adjoining slopes of the San 
Bernardino Range consequent upon recent uplift. 
Before investigating this region it was thought that the Rift, if it continued on south- 
easterly, would be found crossing the San Gorgonio Pass in the neighborhood of Cabazon 
and skirting the eastern base of the San Jacinto Range; but this proved not to be the 
case. Instead, it was found to turn more and more easterly and finally to extend parallel 
with the pass without reaching it. The course of the Rift, then, instead of being in the 
direction of the Salton Sink, is toward the Conchilla Desert north of Palm Spring Station. 
Looking east from a point near the mouth of Stubby Canyon, the gravel mesa thru 
which the Whitewater River issues from the mountains, appears to be faulted upward, 
giving rise to a well-defined escarpment facing north toward the crystalline rocks. This 
northward facing escarpment accords in relative position with the traces of escarpments 
farther north near Oak Glen, and shows that the latest displacement has been the reverse 
of the earlier. The last seen of the Rift is in the sides of the Whitewater Canyon, where 
the gravels are faulted down against the crystallines. East of the Whitewater one enters 
upon the Conchilla Desert over which has been spread the wash of Mission Creek. For a 
distance of 6 or 8 miles, and perhaps much more, the bedrock is completely buried by 
the recent accumulations. 
The San Bernardino Range rapidly decreases in height to the southeast of Mission Creek, 
but appears to be continuous with the desert range lying north of the Salton Basin. The 
latter range of crystalline rocks appears to be separated from the lowlands of the basin by 
a more or less continuous line of barren yellow hills formed of soft late Tertiary rocks. 
Judging from a cursory examination, these yellow hills are separated from the higher 
mountains behind by a structural break indicated by a series of longitudinal valleys. 
A prolongation in a northwesterly direction of the supposed fault line indicated by these 
