Fly Geyser, also known as Fly Ranch Geyser is a small geothermal geyser located on private land in Washoe County, Nevada, about 20 miles (32 km) north of Gerlach. Fly Geyser is located near the edge of Fly Reservoir in the Hualapai Geothermal Flats and is approximately 5 feet (1.5 m) high by 12 feet (3.7 m) wide, counting the mound on which it sits. The geyser contains thermophilic algae, which flourish in moist, hot environments, resulting in multiple hues of green and red, coloring the rocks.
The source of the Fly Geyser field’s heat is attributed to a very deep pool of hot rock where tectonic rifting and faulting are common.
The first geyser at the site was formed in 1916 when a well was drilled seeking irrigation water. When geothermal water at close to boiling point was found, the well was abandoned, and a 10–12-foot (3.0–3.7 m) calcium carbonate cone formed.
In 1964 a geothermic energy company drilled a second well near the site of the first well. The water was not hot enough for energy purposes. They reportedly capped the well, but the seal failed. The discharge from the second well released sufficient pressure that the original geyser dried up. Dissolved minerals in the water, including calcium carbonate and silica, accumulated around the new geyser, creating the cones and travertine pools.
The geyser has multiple conic openings sitting on a mound: the cones are about 6 feet (1.8 m), and the entire mound is 25 to 30 feet (7.6 to 9.1 m) tall.