Page 162 - 1915, Springs of CA.

146 SPRINGS OP CALIFORNIA.
The analyses show that the waters are of the same general primary-
saline and primary-alkaline type, though that of the warm spring is
more concentrated and contains a less proportion of secondary bases
than that of the spring near Black Point. The relatively greater
proportion of silica and the higher magnesium-calcium and chloride-
sulphate ratios of the warm spring are also noteworthy.
South of Mono Lake there is an area of prominent volcanic craters
that are composed largely of fragmental material. These craters are
considered to be of very recent geologic age. Their presence and the
fact that the hot water on Paoha Island issues directly from lava
furnish good evidence that the heat of the springs is derived from
underlying lava that has not yet cooled to the normal temperature
of the surrounding rocks.

CASA DIABLO HOT SPRINGS (MONO 15).
In the southwestern part of Mono County, near the base of the
Sierra, hot water rises at several localities. The principal group,
known as Casa Diablo Hot Springs (PL X, B, p. 140), is situated on
lava slopes bordering Hot Creek, about 200 feet above open meadow
land and at the base of steeper slopes of lava. One main spring here
forms a pool about 15 feet in diameter, in which the water is in vio-
lent ebullition and is thrown to a height of 12 to 18 inches. The dis-
charge is only about 15 gallons a minute, however, so the vigorous
action is probably due largely to steam or other gas. Near the edge
of the pool a temperature of 194° was recorded, which is only about
4° below the boiling point at this elevation (about 7,350 feet), and the
water is probably at the boiling point in the center of the pool. The
water is rendered very turbid by pink clay. Small amounts of vapor
rise in half a dozen small pits that have been dug a few yards south
of this pool. At a distance of 60 to 100 yards north of the main pool
there are a dozen or more pools 2 or 3 feet in diameter in which ob-
served temperatures range from 115° to 187°. They discharge from
one-half gallon to 5 gallons a minute each, and the water forms a
small marshy area, at the edge of which a small bathhouse has been
erected. A log cabin has stood near by for a number of years, for the
springs have long been visited by white people as well as by the
Indians for relief in rheumatic and kindred troubles. Other small hot
vents about 50 to 75 yards northeast of the bathhouse supply a shal-
low pool that discharges perhaps 5 gallons a minute. A quarter of a
mile northeast of these springs there is still another group which
supplies a pool measuring about 20 by 60 yards that discharges 15
gallons of scalding water a minute. In this pool the water rises
mainly from a conical basin. A small pit in the bank near its margin
forms a "paint pot" in which pink mud is kept in motion by bubbles
of steam or other gas. In this material a temperature of 198° (proba-
bly the boiling point) was recorded.