The Lower Geyser Basin encompasses nearly 12 square miles, with most of the thermal features widely scattered in small groups. Some of the groups include the Fountain Group, Firehole Lake Group, White Dome Group, Great Fountain - White Creek Group, and the Imperial Group.

The Lower Geyser Basin possess a large variety of thermal features, including mud pots, geysers, pools, springs, and fumaroles. Great Fountain Geyser is one of the grand geysers in the Lower Geyser Basin. It erupts from a large, terraced platform with massive bursts exploding up to 150 feet high. White Dome Geyser does not have spectacular eruptive displays, but it does have one of the largest pink and white streaked cones in the Park.

The Fountain Group has a large cluster of multi-colored mud pots, and nearby in Pocket Basin is the largest collection of mud pots in Yellowstone. The Fountain Group also includes several spectacular geysers. Fountain, Morning, Clepsydra and Jet geysers dominate the group with periodic and colorful displays.

QUEEN'S LAUNDRY & SENTINEL MEADOWS
Temp 192°F Dimensions 90x135 feet. Depth 26 feet. Queen's Laundry is a member of the Sentinel Meadows Group located on Sentinel Creek. It also called Red Terrace Spring, in reference to the reddish cyanobacteria terraces. It is a remote blue spring located 1.75 miles west of Fountain Flat Drive. In 1880 P.W. Norris, while constructing a road across Fountain Flats, noticed steam rising along Sentinel Creek. The construction crew discovered the large pool with a drainage channel cool enough for bathing. They strung up their brightly colored clothing on stumps and branches and the camp cooks "dubbed it the Laundry, with a variety of prefixes, of which I deemed the most appropriate adheres, and hence the name." The following year Norris constructed a two room bath house with a sod roof. This curious log cabin still remains.

SENTINEL CONE  
Temperature 202.8»F Dimensions; Cone 20 feet high, Pool 8.5x10 feet. Depth 30 feet. Sentinel Cone, also called Steep Cone, is a tall isolated cone rising 20 feet high from the flat sedge meadow. It is located 1.25 miles from Fountain Flat Drive. Sentinel Meadows and Sentinel Creek derive their name from this thermal feature named by Frank Bradley of the 1872 Hayden survey. Three similar cones- Sentinel, Flat and Mound-also project from the meadow and Bradley stated they "appear so much as if they were guarding the upper valley." The mound or cone is built of sinter and void of plant life. Perched at the top of the cone is a punch-bowl-like alkaline spring encircled by a ring or rim or silica. The spring is deep, clear and superheated, reaching temperatures above boiling point, and exhibiting periodic surges.

OJO CALIENTE
Temperature 198.5-202°F Dimensions 12x42 feet. Depth 32.5 feet. The Spanish name, 0)0 Caliente, means "hot eye," and refers to the shape of the spring. It is an isolated, superheated, alkaline spring located on the northern bank of the Firehole River. Surrounding the crater is a heavy shelf of sinter, almost concrete-like in appearance and encrusted with sulfur. On its northern end, Ojo Caliente constantly boils, rising 12-20 inches high. It has erupted as high as two to three feet. The hot spring discharges approximately 100 gallons per minute.

POCKET BASIN MUD POTS 
Temperature 188-200°F Dimensions area size 1300x700 feet. Pocket Basin, on the eastern edge of a thermal crater, formed by a hydrothermal explosion. This steam explosion resulted from overheated ground water that exploded into steam, leaving a crater-like basin. Pocket Basin is in an isolated area along the Firehole River a quarter mile east of Ojo Caliente. It is the largest mud pot concentration in the Park. Steam works its way through silica-bearing silt, producing bubbling mud pots in white to light-brownish-gray. This area is very fragile and delicate. It is an extremely dangerous area and no designated walkways exist.

IMPERIAL GEYSER
Temperature 200°F Interval seconds to 2 hours and occasional dormancy. Duration seconds to 3 minutes. Height 6-80 feet. The geyser became active in 1927. In 1929 a contest among visiting newspaper men named this popular new thermal feature. The eruptions during that year were so violent-reaching 80 to 150 feet high- that its plumbing system may have been damaged creating steam and pressure leakage. The geyser went into dormancy until 1966 when it began a near constant eruption. In 1985 Imperial again went into dormancy, but continues to boil and churn. The 75x100 feet alkaline pool is known for its clear, blue-colored water. The discharge has been estimated at 500 gallons per minute. In 1988 a wildfire swept through this area and even burned logs, projecting from the pool, to the water line.

SPRAY GEYSER
Temperature 199°F Interval 1-5 minutes. Duration 3-10 minutes. Height 10-25 feet. An old and popular small geyser, Spray has had regular eruptions since its early discovery. It has the same energy source as Imperial Geyser at the base of South Twin Butte. It is one of the few geysers that has a longer eruption time (duration) than the interval between eruptions. When it erupts there are two main jets of water. The main column jets at a 70° angle and both jets spray with some of the water dissipating into steam. A lush mat of chocolate-brown-colored cyanobacteria and algae cover the vent and vicinity.

OCTOPUS SPRING
Temperature 184-196°F Dimensions 27x46.5 feet. Depth 25 feet. Octopus Spring's drainage channels radiate like the arms of an octopus, hence its name. The spring sits at the base of a glacial moraine in an isolated location off the road approximately 800 feet up the White Creek Drainage from Great Fountain Geyser. Only a narrow foot trail leads to the crystal blue pool. The pool has a thin, scalloped, sinter sheet o rshelf extending 1 to2feetaround the edge and part way down the run-off channels. A steady discharge, estimated at 75 to 100 gallons per minute, feeds the extensive and colorful microbial mats. These microbial mats have had extensive study, and geometric and grid patterns in the mats are growth studies and extraction of lamination samples.

GREAT FOUNTAIN GEYSER  
Temperature 202°F Interval 8-12 hours. Duration 45-60 minutes. Height 75-150 feet. Great Fountain Geyser is one of the grand geysers of Yellowstone. It has the distinction of having the first written description recorded by the 1869 Folsom-Cook Expedition. But it remained unnamed until the 1872 Hayden Survey. The intricately terraced sinter cone is 150 feet in diameter with a 14x20 foot crater. Eruptions begin about one hour after the crater fills and the first overflow spills onto the terraces. The overflow period is longer in spring and fall. A few minutes before the eruption water violently surges and boils, starting an eruption. Bursts may reach up to 200 feet, but average 100 feet. The hour-long eruption has several phases.

WHITE DOME GEYSER
Temperature 188°F Interval 12-24 minutes, Duration 2 minutes, Height 10-30 feet. Named by the 1871 Hayden Expedition, the name is descriptive of the white-colored deposits found in the area. The sinter cone, built upon an older hot spring mound, is 20 feet high. It is an older cone built up by spray. The orifice is now less than four inches in diameter and continued internal deposits may seal it up. An eruption occurs moments after splashing begins. The eruption starts with jets of water progressing into steam and spray. The geyser is temperamental and irregular, but intervals between eruptions can occur from ten minutes to one and a half hours.

PINK CONE GEYSER
Temperature 161°F Interval 6-16 hours and occasional dormancy, Duration 30 minutes to 3 hours. Height 20-35 feet. The Hayden Survey named this feature for the beautiful shell-pink color of the cone's sinter. It stands 18 inches high. Manganese and iron oxides are responsible for the dark color. During the construction of the Firehole Lake road in the 1930s the mound was cut, and the road now passes within 13 feet of Pink Cone's crater. It has had periods of dormancy and its regularity changes too. It erupts with a steady blaster column of water with pauses and renewed vigor. There is no apparent underground connection with other thermal features.

BEAD GEYSER
Temperature 172°F Interval 25-33 minutes. Duration 2.5 minutes, Height 15-25 feet. Professor T.B. Comstock, geologist of the 1873 Jones Expedition, named present day Labial Geyser, located 130 feet north, Bead Geyser. Labial Geyser was known for its geyser eggs, small marble to egg sized sinter beads, which subsequently were collected by early tourists. However, the present day Bead Geyser is appropriately named. Its shallow 10x15 foot crater has a beautiful and intricate beaded surface. Not only does Bead have a beautiful crater, but it is perhaps the most regular geyser in Yellowstone, with little variation in its interval and duration. Bead's vent has been probed to a depth of 7.5 feet below the lip.

NARCISSUS GEYSER  
Temperature 205°F Interval 2-8 hours. Duration 5-10 minutes. Height 10-15 feet. During the 1880s The Hague Party named Narcissus Geyser after a Greek myth about a youth who fell in love with the reflection of his image in a pool. On his death the gods changed his reflection into a flower called narcissus. This geyser is isolated behind a fringe of trees 550 feet north of Pink Cone Geyser. Nodules of sinter colored a soft beige or pink line the six-foot-diameter crater. A clue to a pending eruption is a slow rise of water in the crater, and it begins to overflow one hour before an eruption. Splashing triggers jets of water 15 feet and sometimes 20 feet high. After an eruption the crater drains and empties the bowl.

STEADY GEYSER
Temperature 199°F Interval none. Duration constant. Height 2-15 feet. Named in 1871 by the Hayden Expedition for its constant action. The name changed to Black Warrior Geyser in the 1920s, but the old name reverted back in the 1930s. It is the largest constantly erupting geyser in Yellowstone and the world. Steady Geyser, located on the edge of a small lake near Hot Lake, has a dark gray-brown mound, colored by manganese oxide, built in an irregular mass of geyserite. This geyser has two vents and at times one vent may become dormant while the other continues to erupt. Steady has no known subterranean connections to other features in the Firehole Lake Group.

SILEX SPRING
Temperature 193°F Dimensions 35.5x39.4 feet. Depth 27 feet. It is unknown when or by whom this colorful blue spring was named, but the name Silex may refer to the word silica. Some believe it may refer to the Silex coffee percolator. The spring boils occasionally and, periodically large bubbles of gas rise to the surface. The 1959 earthquake caused it to erupt and increased the flow. The discharge is now 75 to 100 gallons per minute. There are underground connections to Celestine Pool, a similar nearby hot spring.

FOUNTAIN PAINT POT
Temperature 202.8°F Dimensions 80x40 feet. Fountain Paint Pots was originally named "Mud Puff" by the 1871 Hayden survey and later turn-of-the-century tourists called it Mammoth Paint Pots. But guide books referred to the area as Fountain Geyser and Pain pots and the name was adopted in 1927. The mud is composed of clay and fine particles of silica broken down by acids and grinding action. The tinting of the mud in colors of pink and gray from iron oxides is derived from the original rock. The bubbling action results in escaping steam and gases - mainly carbon dioxide and hydrogen sulfide. In the spring and early summer the mud is thin and the pots boil. By late summer and fall there is less moisture and the mud is thicker, creating unusual shapes and formations.

FOUNTAIN GEYSER
Temperature 199.2°F Interval 1-12 hours and occasional dormancy. Duration 30-60 minutes. Height 50-75 feet. Lt. G.C. Doane referred to the pool filled craters as "clear fountains" in 1870, but it was given its official name by the 1871 Hayden Expedition. Fountain Geyser, located next to Morning Geyser-the largest geyser in the group, usually has long periods of dormancy of one or more years, it was very active between 1870 and 1910 when a hotel was built nearby, but activity declined and in 1929 became dormant until after World War 11. Since the 1959 earthquake the geyser has been irregular, with periods of dormancy. During Fountain's quiet phase the water is azure blue and tranquil. About an hour before an eruption a stream of bubbles rises to the surface. The water begins to boil and churn resulting in an eruption. Following an eruption the water level drops one to two feet below the rim.

CLEPSYDRA GEYSER
Temperature 197.3°F Interval seconds to 30 minutes. Duration nearly constant. Height 10-40 feet. Professor T.B. Comstock.a member of the Army Corps of Engineers Survey, named this geyser in 1873 for its regularity "like the ancient Greek water clock." Since the 1959 earthquake Clepsydra spouts as a nearly constant geyser, erupting from four vents. Two types of eruptions characterize Clepsydra. The constant splash-type eruptions from the highest vents send jets of water and steam 10-15 feet in all directions for about three minutes. The more powerful eruptions called "wild phase" activity send steady jets 20-40 feet from all four vents for three to six hours. Clepsydra discharges nearly 675 gallons per minute.

JELLY GEYSER
Temperature 196.7T Interval 15-90 minutes. Duration seconds to 2 minutes. Height 1-10 feet. Professor Theodore Comstock of the Captain Jones Party first described this feature in 1873, but its name may be derived from geologist Walter Weed, who in 1888 described the pool as "clear-as-glass, green water." He believed algae helped in the formation of sinter from "algous jelly" to hard sinter. It has one of the largest craters in the Fountain Group, measuring 16.5x30.6 feet. The craters edge has delicate scalloped sinter. The indication of an eruption starts when the crater is full. The only warning before an eruption is a slight boiling progressing into splashing. The eruptions are small, discharging only 10 to 15 gallons per minute.