Page 87 - 1915, Springs of CA.

HOT SPRINGS. 83

springs. Shales extend from the western border of the lava to the
coast at Point Arena.1

ORRS ttOT SPRINGS (MENDOCINO 20).
Orrs Hot Springs (Pi. IV, B, p. 32) issue along the eastern edge of
the main fork of Big Biver, which here flows in a deep, wide canyon.
The locality is a resort and stage station on the road between Ukiah
and Mendocino. A hotel and two or three cottages furnish accommo-
dations for about 50 guests, and tents are erected during the summer
when needed. Five springs rise near the hotel. They range in
temperature from about 70° to 104° and have individual flows of 4 or
5 gallons a minute. One of the springs rises in a small swimming
plunge, and the others supply tub and plunge baths. Near one side
of the plunge is also a drinking spring, 85° in temperature and of
seeping flow, and at ihe edge of the stream, 250 yards below the
main group, another storing that is used for drinking issues with an
observed temperature pf 63° and a flow of about 2 gallons a minute.
A hydrocarbon gas that was formerly used for lighting issues at the
main springs, but the earthquake of April 18, 1906, apparently so
altered the points of escape of the gas that in 1909 it was no longer
used. The water is njoticeably sulphureted, but an early analysis 2
indicates that it is only moderately mineralized, though it has a con-
siderable silica content.
The rocks of the region are of the Franciscan formation and near
the springs consist of crushed sandstone with some chert. Serpen-
tine and siliceous shales were noted on the higher slopes of the
canyon.
The effect of the San Francisco earthquake on the springs sug-
gests that faults subsidiary to the San Andreas rift exist in this part
of the mountains. Local evidence of alteration in the sediments,
however, indicates tha|t crushing alone may be sufficient to account
for the issuance of warm water at this point, along the bottom of
the deep canyon.
THE GEYSERS (SONOMA 4).
The Geysers of Sonoma County have become widely known, both
for their scenic features and for their scientific interest, but it is only
proper to state that tfyere are no true geysers, intermittently throw-
ing out hot water, at this place. The locality is said to have been,
first brought to publib notice in 1846 by a party of hunters. Its
unusual character soon became of more than local interest, a resort
1 Shale cliffs at the port of this settlement form a noticeable feature from the ocean, and expose beds
that dip 40° to 65° northward. A| 4-foot bed of oil sand is also exposed near the boat landing, and somes
prospecting for oil has been done near by.
2 California State Mineralogist Tenth Kept., p. 313, 1890.