390 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 
in many parts of the Santa Cruz Mountains which can not be enumerated. There were 
also several such slides on the granite slopes of Montara Mountain, farther north in the 
San Francisco Peninsula. 
In the Coast Ranges to the north of the Bay of San Francisco, earth-avalanches were 
not so common away from the coast as they were in the Santa Cruz Mountains. There 
were, however, two notable ones which deserve mention here. The first of these is the 
Maacama slide, 6 miles east of Healdsburg. (Plate 124, B.) The slide is about 0.125 
mile wide at the top, and 0.5:mile long. The rock is a stratified volcanic tuff, and the 
slip was down the dip of the beds. The avalanche cut its way thru a fir forest and 
dammed Maacama Creek. The other is the earth-avalanche which, on May 1, 1906, 
dammed Cache Creek to a depth of 90 feet at a point 4 miles below the confluence of 
the north and south branches of the creek. The rock which fell is red sandstone. The 
width of the slide is 300 feet and its height is 500 feet. The dam thus formed broke 
one week later. This earth-avalanche can not be so directly referred to the earthquake 
of April 18 as the others heretofore described, but it was probably indirectly caused by 
the shock. 
BHARTH-SLUMPS. 
By far the most common manifestation of landslide phenomena was that here referred 
to as earth-slump. It would be wearisome to attempt to mention all the various earth- 
slumps stimulated by the earthquake, even if information were sufficiently detailed to 
make this possible. Only two of the more important slides which have come under the 
observation of geologists will be noted. 
Cape Fortunas earth-slump (F. E. Matthes).—This landslide, immediately south of Cape 
Fortunas, is by far the most extensive one on the northern coast. (See plate 127a, B.) 
In May, 1906, it projected into the ocean for about 0.25 mile, like a hummocky headland 
of irregular outline; indeed, it formed a new cape on the coast-line, but will doubtless 
rapidly be cut back by the action of the waves. Its length, in the direction of its move- 
ment toward the ocean, is estimated at little short of a mile; its width varies from 0.25 
mile to 0.5 mile. Its total descent, from the summit of the higher scarps at its head to 
the level of the sea, is probably less than 500 feet. Its surface is exceedingly irregular, 
with many large humps and hollows. Over large areas the sod is more or less rhythmi- 
cally, broken by deep cracks extending at right angles to the direction of movement. 
These cracks are only a few feet apart, and the sod-blocks between them lie mostly in 
tilted attitudes, making the area exceedingly difficult to traverse. The general aspect 
is not unlike that of a much crevassed glacier. In some places, however, the mass seems 
to have been torn apart so completely that the sod is not merely broken but almost 
swallowed up or buried, the browns and yellows of the under soil being the prevailing 
tints. Around its head are a number of steep scarps, from 100 to 200 feet high. They 
are especially prominent on the north side, and again toward the southeast; but over 
considerable stretches between these two sets, the broken surface of the slide joins the 
unbroken hillsides to the east without significant offset. Owing to this, the slide is 
easily approached from the wagon road (from Centerville to Cape Town), which passes 
close by its head. The longitudinal profile of the landslide is one of gentle slopes for 
the most part; its declivity is not at all great, and in a few places even reversed slopes 
occur. Its noteworthy feature is not its vertical drop but its great forward movement. 
In a sense it has flowed like a partially plastic mass, expanding and advancing 0.25 mile 
‘beyond the coast-line, but descending only a few hundred feet. 
In its general aspect, as well as in the nature of its movement, the Cape Fortunas 
landslide is altogether different from those observed farther south, particularly along 
the mountainous coast both north and south of Point Delgada, which, in effect, did little 
