388 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 
Inland from the coast there were numerous earth-avalanches caused by the earth- 
quake on the walls of steep canyons. One of the most noteworthy of these was on the 
north side of a short but deep canyon west of Chittenden and close to the line of the 
fault.. (Plate 1264.) The rocks composing the side of the canyon are the bituminous 
shales of the Monterey series. The slope rises very steeply for about 500 feet and was 
quite dry before the earthquake, altho it was covered with spring vegetation. Areas 
of bare rock appeared thru this vegetation. At the time of the shock several earth- 
avalanches were started, and these slid suddenly down the slope, part of the material 
filling the bottom of the canyon and part remaining on the less steep lower portions of 
the slope. The larger masses were broken off up near the brink of the canyon. There 
was apparently little or no rotation of the sliding mass. The result was to gorge com- 
pletely the lower part of the canyon with rock débris, to widen the upper part of the 
canyon, and to expose extensive surfaces of unweathered rock. 
On Deer Creek, in the Santa Cruz Mountains, an extensive earth-avalanche started 
near Grizzly Rock and moved westward down a steep, narrow canyon for about 0.25 
mile. (Plates 124p and 125a.) It then changed its course thru an angle of about 60° 
as it entered a wider canyon of lower grade, and following this for another 0.25 mile, 
finally stopt at the Hoffmann Shingle Mill, which was wrecked. <A fine growth of red- 
wood, some 200 feet in height, was mowed down, and covered to the extent of 10 acres 
or more with from 30 to 60 feet of débris. The trees were from 3 to 10 feet in diameter. 
The main canyon was filled with earth and rock for an average width of 80 yards and 
a length of 400 yards. -'The entire area of the slide‘was about 25 acres. The difference 
in altitude between the point where the slide started and the shingle mill, where it stopt, 
is 500 feet. According to Mr. G. A. Waring, the slide material has a depth of 300 feet 
and is composed of soil, clay, and shale. Mr. E. P. Carey, who examined and photo- 
graphed this interesting earth-avalanche, states that it originated in rock that broke 
away in pieces from the steeply inclined slope at the head of the gulch, leaving a large 
theater-like space, the bare, light-colored rock walls of which were in sharp contrast 
with the surrounding green vegetation. The movement was faster in the center or 
deepest part of the gorge than on the margins. The rock was in general piled up higher 
along both sides than in the center, and many pieces became entangled in the standing 
or uprooted trees. A steep-walled tributary to the southeast of the main gulch supplied 
rock material to the main avalanche, and the 2 streams joined much as confluent glaciers 
do. The material involved in the avalanche showed every gradation from powder to 
angular pieces 30 feet or more in diameter. The surface was uneven thruout. Near 
the mill a man was killed by a tree that fell as the avalanche was advancing. 
Mr. Carey also reports another earth-avalanche located on the Petty ranch, about 
4 miles southeast of the one just described. Here a huge rock mass, which embraces an 
area of about 12 acres at the headwaters of Cauley Gulch, broke away from a ledge and 
dropt, leaving a vertical scarp of 40 feet or more. The rock mass in this case was not 
shattered. It practically maintained its integrity. The narrow gulch below was un- 
favorable for free downward movement. As the block readjusted itself, its upper surface 
became nearly level, but was lower at the foot of the scarp than at its outer edge, thus 
indicating that it had suffered rotation. 
At a point about 1.25 miles west of the Mindego sink, on the ranch of Andrew Stengel, 
an earth-avalanche is reported by Mr. Albert C. Herre. It is on a small tributary of 
Alpine Creek, and about 4 miles southwest of the San Andreas fault at the point where 
the latter crosses Black Mountain into the head of Stevens Creek Canyon. The creek 
here is in a narrow, steep-walled canyon in the bituminous shale of the Monterey series. 
The soil on the canyon side was very shallow, and at the time of the earthquake it was 
shaken down into the bottom of the canyon, leaving the walls absolutely bare in places 
