Pyramid Lake is on the Pyramid Indian Reservation, about 48 km northeast of Reno and lies along the Walker Lane, a major right-lateral strike slip fault zone in western Nevada. The Needle Rocks are at the northeast corner of Pyramid Lake (Sec. 12, T26N, R20E and Sec. 6, 7, T26N, R21E), along north-northeast-striking faults that are presumed to be part of this Walker Lane fault zone (Bonham, 1969). Warm springs are also present at Pyramid Island (Sec. 3, T24N, R22E) and on Anaho Island (Sec. 16?, T24N, R22E); both localities are also within the Walker Lane fault zone.
Both the Needle Rocks and Pyramid Island are spectacular masses of tufa that were deposited in Pyramid Lake when its level was higher than at present. The collection of tufa into needles, spires, and pyramids is believed to be related to underwater warm springs (Russell, 1885), and divers reported that underwater hot springs are present near the Needle Rocks and The Pyramid.
Springs at the Needle Rocks are reported to range from 58°C (Benson and others, 1995) or 66°C (Grose and Keller, 1975b) to a maximum of 98°C (Waring, 1965), which is near boiling for that elevation. A number of the springs are shown on the Needle Rocks 7.5minute Quadrangle map. In the early 1960s Western Geothermal, Inc. drilled three geothermal wells at the Needle Rocks. The deepest of these was 1,795 m, and another was about 1,220 m deep. The maximum recorded temperature was about 116°C. From examination of drill cuttings from the deepest well, it is believed that Tertiary basaltic andesites overlie Mesozoic metamorphic rocks at about 1,540 m (H.F. Bonham, written commun., 1964). This well flowed continuously after its completion, but geysered or pulsed, a complete cycle taking about 1 minute. A 35-second eruption, with hot water reaching 10 m in height above the well, was followed by 32 seconds of diminished activity. During this period the well flowed at a rate of about 450 L/min. A thin film of siliceous sinter (geyserite) collected on the well casing during this time; a slight odor of H2S was also noted (H.F. Bonham, Jr., written commun., 1964). Mariner and others (1974) reported that their best estimate of the thermal reservoir temperature is 137°C, using the silica (adiabatic) geothermometer. Na-K-Ca geothermometer temperatures are higher; a sample considered reliable yielded a Na-K-Ca estimated temperature of 213.9ºC and a K-Mg estimated temperature of 228.3 (GeothermEx, 2004). Benson and others (1995) reported a temperature of 85.3°C for water flowing from the Needles well.
Photos
Western Geothermal Inc Needles No. 1 well at The Needle Rocks, Washoe County, shortly after drilling in 1965.
Needle Rocks geothermal well.
Airphoto
Western Geothermal Inc. Needles No. 1 well at The Needle Rocks, Washoe County, in 1971.
Flowing well at the Needle Rocks, north of Pyramid Lake.
Flowing well at the Needle Rocks, north of Pyramid Lake.
The Needles - Western Geothermal, open well.
Tufa formations at Pyramid at low water.
The Needle Rocks.
The Needle Rocks.