Nathaniel P. Langford, a member of the 1870 Washburn Expedition-who named many of the thermal features of the Upper Geyser Basin, later stated; "We gave such names to those of the geysers which we saw in action as we think will best illustrate their peculiarities." Those names include Old Faithful-named for its regular eruptions; Beehive Geyser-with its bee-hive shaped cone; and Riverside Geyser-named for its location on the Firehole River.

The Upper Geyser Basin, approximately two square miles in area, contains the largest concentration and nearly one-quarter of all of the geysers in the world. A variety of thermal features exist here: spouting geysers, colorful hot springs, and steaming fumaroles.

The Upper Geyser Basin is the home of Old Faithful, the most famous and celebrated geyser in the world. The 1870 Washburn Expedition camped near Old Faithful and discovered the geyser had frequent and regular eruptions over 100 feet. They dubbed the geyser Old Faithful. It erupts once approximately every 45 to 90 minutes, depending on the duration of the previous eruption. To be able to predict your own eruption of Old Faithful refer to appendix A on page 115.

OLD FAITHFUL
Temperature 199° Interval 30-120 minutes. Duration 1.5-5 minutes. Height 110-185 feet. The Washburn Expedition in 1870 named Old Faithful for its nearly regular schedule of eruptions. It is the grand old geyser of Yellowstone because of its frequent and predictable eruptions. The intervals between eruptions average between 45-90 minutes and the average duration is about four minutes. To predict the next eruption, its first continuous surge is timed until the final splash. If the total eruption is less than four minutes, the next eruption will occur in approximately 40-60 minutes. If the eruption is four minutes or longer, the next interval will be 75-100 minutes.

ARTEMISIA GEYSER
Temperature 191-202°F Interval 6-16hours. Duration 10-30 minutes. Height 10-25 feet. Geologist Walter Weed named this feature in 1883 for the sagebrush-like coloration of the deposits. Artemisia is the scientific name for sagebrush. Artemisia Geyser has the largest ornamented crater of any thermal feature in Yellowstone. The popcorn-like sinter has formed ridges by evaporation and small pools 30 feet from the 55x60 foot crater. An eruption is signaled by a sudden rise of water in the crater and heavy overflow. The water begins to boil and jets rise to 20-25 feet. After an eruption, water drops nearly two feet in the crater.

MORNING GLORY POOL
Temperature 171.6°F Dimensions 23x26.6 feet. Depth 23 feet. A deep, funnel-shaped pool with a dark blue center. The resemblance to the corolla and color of a morning glory is responsible for its name in the early 1880s. It has been a popular thermal feature and a symbol of Yellowstone. The early stagecoach and automobile road came within a few feet of this pool until 1971 when the road was rerouted. Early visitors carelessly removed the delicate scalloped border and dumped debris into the pool. In 1950 the water level was lowered by siphoning which induced the pool to erupt. Socks, bath towels, 76 handkerchiefs, $86.27 in pennies, $8.10 in other coins came up; in all, 112 different objects were removed from Morning Glory. The debris had reduced the flow of water and contributed to the decline in temperature, causing bacteria to grow in the cooler yellow and orange edges of the pool.

RIVERSIDE GEYSER
Temperature 201.2°F Interval 7 hours. Duration 20 minutes. Height 75 feet. The 1871 Hayden Expedition officially named this geyser for its location on the bank of the Firehole River. Riverside is an isolated geyser, with its own plumbing system, and it has regular, predictable eruptions. About one to two hours before an eruption water begins to overflow and surge in the crater. Forty to 50 minutes before an eruption water may boil and splash from the crater. A heavy surge or splash then triggers an eruption. The column of water arches over the Firehole River at about a 70° angle and at times spans the width of the River. The eruption peaks during the first five minutes and then begins to subside gradually, followed by a steam phase.

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SPA GEYSER
Temperature 193°F Interval Irregular (dormancy). Duration minutes to several hours. Height 20-50 feet. Geologist Walter Weed in 1887 named this thermal feature apparently after a curative mineral spring in Spa, Belgium. Spa Geyser has always had an interconnecting relationship with Grotto and Rocket geysers. Spa usually erupts during a long eruption (more than 2.5 hours) of Grotto. If it does not erupt during an eruption of Grotto the 36-foot diameter basin then usually overflows with boiling water. An eruption is characterized by a full and overflowing basin. Boiling and surging, to a height of 3-4 feet, trigger a series of explosive bursts lasting several minutes to several hours.

ROCKET GEYSER
Temperature 200°F Interval 1 hour to 2 days (usually erupts during Grotto Geyser's eruption). Duration follows eruptive pattern of Grotto Geyser, Height 3-10 feet (with major eruptions up to 50 feet). Rocket was named before 1904 and may have been named by geologists Arnold Hague and Walter Weed. The name is descriptive of its eruption. Rocket Geyser erupts in union with Grotto Geyser. During an eruption of Grotto, Rocket, located north of Grotto along an interconnecting bridge of sinter, plays in union, sending steady splashes and jets 3 to 10 feet high. Occasionally Rocket has a major eruption about 1-2 hours after Grotto starts. During a major eruption Grotto becomes silent and Rocket sends an eruptive jet up to 50 feet high.

GROTTO GEYSER
Temperature 201 °F Interval 1 hour to 2 days. Duration varies (3 hours for short mode and 9-13 hours for long modes). Height 20-30 feet. The 1870 Washburn Expedition named this unusual feature for the "winding apertures penetrating the sinter." It is an unusual shaped formation nearly 8 feet high. The club-shaped pillar and two adjoining arches formed from fallen trees. The accumulation of sinter from eruptions and evaporation has changed their original shape into eerie formations. The transfer of thermal energy from Giant Geyser to Grotto in 1955 has resulted in a productive feature. The eruptions consist of a series of powerful splashes, steam and the discharge of nearly 150 gallons per minute. Deep gurgling and splashing sounds are constantly emitted from the vent.

DAISY GEYSER
Temperature 192-204°F Interval 78-144 minutes. Duration 2.5-4.5 minutes. Height 75-150feet. It is uncertain how Daisy received its narne. Confusion exists in early descriptions of the Daisy Group, and this geyser may have originally been called Comet by Dr. F. Hayden in 1878. Daisy Geyser is the most reliable and predictable of the major geysers in the Upper Geyser Basin. Its average interval is between 85 to 100 minutes. However, wind and thunderstorms can delay an eruption up to a half hour. Atmospheric pressure moves water within the underground plumbing system much as it does in a barometer. Splashing begins approximately 20 minutes before an eruption from the larger of the two cones, and 10 minutes before in the smaller cone. Heavy splashing leads to an eruption and reaches its maximum height in 45 to 60 seconds. The water jets at a 70° angle.

COMET GEYSER
Temperature 201.6°F Interval steady (irregular). Duration steady. Height 5-15 feet. Dr. F. Hayden in 1878 originally named this geyser Spray. Due to confusion of early geyser descriptions, names of the Daisy Group became switched and the error was never corrected. Comet has the largest cone in the Group, suggesting it is a powerful geyser. However, water rarely splashes out of the crater, and rarely reaches 6 feet high. It has been a steady geyser with little change since its discovery. The only variance in its eruptive pattern is attributed to the eruptions of Splendid and Daisy geysers and Brilliant Pool. This indicates subterranean connections with others in the Group.

SPLENDID GEYSER
Temperature 199.4°F Interval infrequent to dormancy. Duration 2-10 minutes. Height 120-200 feet. P.W. Norris named this geyser in 1880 for its spectacular eruptions. Splendid was considered one of the major geysers before 1898, when it became dormant. It was dormant until 1951-with only one eruption in 1931-and active until 1959 when it became dormant again. In 1971 Splendid resumed its infrequent activity. An indication of a pending eruption is surging up to 30 feet. The water rises from the crater like a fountain and begins erupting. There is an estimated discharge of 40,000 gallons during each eruption.

PUNCH BOWL SPRING
Temperature 199°F Dimensions 12 feet diameter. Depth 30 feet. The name, descriptive of its punch bowl shape, was given by members of the 1871 Hayden survey. The crater is a raised rim of sinter about 30 inches high. Water constantly boils and bubbles around the edge resembling a large, bubbling cauldron. During the turn of the century, hot water was piped from Punch Bowl to a tent camp a quarter of a mile to the north. It is one of the few thermal features on which human tampering has had no disastrous effect. Ribbons of bright green and orange cyanobacteria line the run-off channels. No underground connections are known to exist with other springs.

MASTIFF GEYSER
Temperature 202°F Interval frequent small eruptions. Duration seconds to minutes. Height 1-30 feet. Around 1900 the Hague Party named Mastiff Geyser for its position as a watchdog close to Giant Geyser. Mastiff is located only 22 feet north of Giant, is closely related to Giant and exchanges energy with it. Before 1951 Mastiff was an inactive geyser and was considered dormant. During that year energy shifted from Giant to Mastiff and Catfish geysers and they both erupted nearly 100 feet high. By early 1952 the energy shift ceased and since then Mastiff has spring-like qualities with weak splashing from its 4 foot, bacteria and algae covered cone. The vent was probed to a depth of 11 feet below the lip.

GIANT GEYSER
Temperature 202.7°F Interval 6-14 days to dormancy. Duration I hour. Height 150-250 feet. Named by the 1870 Washburn Expedition for its size and long duration, it is one of the major geysers of Yellowstone. It has only erupted several times since 1955. Before 1955 hydrothermal activity shifted cyclically from Grotto Geyser to Giant every four to five years, but since the 1959 earthquake, energy has vented through Grotto Geyser. Giant still possesses great thermal energy. It roars, splashes, steams and has one of the hottest vents in the Basin. The cone is also impressive; broken on one side, it is 12 feet high, with an inside diameter of six feet.

OBLONG GEYSER
Temperature 196°F Interval 4-13 hours. Duration 5-7 minutes. Height 20-40 feet. The 1872 Hayden Expedition named this geyser for the shape of its crater. The greenish-blue tinted pool and elaborate sinter formations around the crater are as impressive as an eruption. Even though Oblong is not considered a major geyser, an eruption discharges a high volume of water. During the quiet interval there is a slow rise of water in the crater which can take one to three hours to fill. Eruptions are difficult to predict since there are occasional periods of turbulence and overflow. When it does erupt, a fountain of water wells up, setting off jets of water accompanied by splashing and steam. Splashing and evaporation are responsible for the elaborate growth of the sinter formations.

BEAUTY POOL
Temperature 164-175°F Dimensions 60 feet in diameter. Depth 25 feet. This spring and nearby Chromatic Pool are among the most colorful pools in the geyser basins. Their colors begin with a deep blue center radiating out to yellow, orange and red. The two pools are related. When one pool begins to overflow, the water level in the other drops. This periodic shifting in energy is accompanied by a 10°F change in temperature. In recent years the water temperature has cooled, allowing an increase in bacteria and algae growth and a resulting change in color.

TURBAN GEYSER
Temperature 197°F Interval 15-25 minutes. Duration 4-5 minutes. Height 5-20 feet. Dr. A.C. Peale, geologist for the 1872 Hayden Party, named this geyser for the resemblance "of some of the globular masses of sinter in its basin to a Turkish headpiece." Turban and Grand geysers are closely associated and have a complex functional relationship. Turban's crater has a raised sinter rim and lies north of Grand's large, shallow basin. Normally Turban erupts every 15-25 minutes, except during an eruption of Grand. Grand erupts only at the start of an eruption of Turban. The rising water in Turban's crater triggers an eruption in Grand. Turban plays constantly during Grand's eruption and for an hour after until Grand returns to normal.

GRAND GEYSER
Temperature 201°F Interval 6-15 hours. Duration 9-16 minutes. Height 140-200 feet. The power and spectacle of a Grand Geyser eruption inspired the name given by the 1871 Hayden Expedition. It is one of the few major geysers that has not changed considerably since its early discovery. This fountain-type geyser erupts from a shallow basin which slowly fills with water over a 5 hour period. Two adjoining geysers, Turban and Vent, are separated by a thin narrow bridge. Grand's eruptive cycle depends on the activity of these two geysers and West Triplet and Rift geysers. Grand only erupts at the start of a Turban active period. A slight ebb in Turban's eruption may signal an eruption of Grand with an explosion, pulsating vibration, and jets of water. During eruption Grand usually has 1 to 6 bursts lasting 1 to 10 minutes each.

SPASMODIC GEYSER
Temperature 200°F Interval hours (irregular). Duration minutes to hours. Height 3-15 feet. Dr. A.C.Peale, geologist with the 1878 Hayden survey, named Spasmodic Geyser for its erratic eruptions. This geyser plays from a collection of vents-estimated at 20-centered around two large craters. When Spasmodic is in full eruption water jets from a few inches to several feet high from the numerous vents. The two pools also erupt up to 15 feet high, with intermittent pauses and boiling, pulsating water. Spasmodic and Penta geysers, and possibly Sawmill Geyser, have subterranean connections. When the small, nearby Penta Geyser erupts, all activity in Spasmodic ceases.

SAWMILL GEYSER
Temperature 189-207°F Interval 1-3 hours. Duration 15-90 minutes. Height 5-40 feet. A topographer of the 1871 Hayden Expedition named this geyser for its whistling sound, reminiscent of a large sawmill in operation. The crater of this fountain-type geyser is empty between eruptions. A gurgling sound and then a sudden filling of the basin indicates a pending eruption. Pulsating jets of water erupt through the pool producing a puffing or whistling noise. An eruption produces a large, steady discharge of water to the run-off channel. Subterranean connections exist between Sawmill, Tardy and Penta geysers and probably Spasmodic Geyser. Sawmill's vent was probed to a depth of 13.5 feet.

CRESTED POOL
Temperature 200°F Dimensions 25x30 feet. Depth 42 feet. Dr. F.V. Hayden first described this pool in 1871 and noted its "unnatural clearness" and the "delicate tracery of pure white silica." Photographer W.H. Jackson took the first photograph of Crested Pool during the 1871 expedition. Other than the addition of a board walk, the pool has changed very little when compared to the early photograph. It is a superheated pool and the edges are in a constant state of vibration with occasional surges of hot water. It has erupted to 6 to 8 feet. Temperatures recorded near the bottom of the pool have reached 237°F. Crested Pool took the life of a young boy who unknowingly ran into the steam and the pool in the spring of 1970. A railing now surrounds the board-walk along the edge of the pool.

CASTLE GEYSER
Temperature 200°F Interval 9-11 hours. Duration 1 hour. Height 60-90 feet. Members of the 1870 Langford-Doane Expedition named this feature for the "resemblance to the ruins of an old castle." The large sinter cone is nearly 12 feet high with a diameter of 20 feet at the top. Castle was an irregular geyser, with periods of dormancy, before the 1959 earthquake. Since the earthquake, it has been a regular, easily predictable geyser. The water phase of an eruption lasts about 15 minutes and a steam phase, similar to a steam locomotive, lasting an additional 45 minutes. Subterranean connections exist between Castle and Crested Pool.

LION GROUP
Temperature 202°F Interval 2-5 hours (irregular). Duration 2-4 minutes. Height 30-60 feet. Four geysers comprise the Lion Group-Lion, Lioness, Big and Little Cub geysers-and all have subterranean interconnections. Col. P.W. Norris named the main geyser in 1881 for its resemblance, when viewed from the south, to the body and maned head of a reclining lion. Lion Geyser has the largest cone and usually has 2-4 eruptions per cycle-lasting from 4 to 36 hours-at intervals of two to four hours when it is active. Often, however, it can be 2 to 14 days between cycles. Preceding an eruption is a sudden rush of steam, like the roaring of a lion. There is a heavy discharge of water for a minute or so which declines into a steam phase for the remainder of the duration. The other features in the group also have dormant periods.

EAR SPRING
Temperature 202°F Dimensions 4x6 feet. Depth 4 feet. A small but popular spring in the shape of a human ear. In 1890 geologist Walter Weed originally named this Oyster Spring for its shape and later early tourists called it Devil's Ear. Geyserite or sinter form the ornate encrustation around its edge and along the overflow channel. It is a super-heated spring reaching temperatures of205°F, and it is usually in a state of ebullition or boiling. Surging, strong boiling and heavy discharge occur after an eruption of Giantess Geyser. After the 1959 earthquake this spring had a minor eruption and produced a heavy discharge. There are subterranean connections with nearby springs.

AURUM GEYSER
Temperature 200°F Interval 3-4 hours. Duration 60 seconds. Height 10-30 feet. A small geyser named for the soft pastel colors surrounding the vent. Iron oxides are responsible for staining the sinter its peach and golden colors. Intricate, scalloped formations and unusual and symmetric patterns have formed around the vent. In the past Aurum has had long periods of dormancy, but since 1985, with the exception of 1988, it has been a regular, active geyser. Splashing begins an eruption which usually jets 10-15 feet high. There are no known underground connections with other springs.

DOUBLET POOL
Temperature 194.4°F Dimensions 9x25 feet. Depth 8 feet. Doublet Pool is two hot springs together forming a sapphire-blue-colored pool. A sinter ledge extends over the surface of the pool and two feet below this is another ledge, indicating that the water level was lower at an earlier time. The pool produces a periodic, inaudible thumping which can be felt, more than heard, when standing close to the pool. The water also slightly pulses during the thumping process. It has erupted in the past, once during an eruption of a nearby geyser and after the 1959 earthquake. These eruptions were minor with boiling activity only two feet high. The overflow is small, discharging only one to 20 gallons per minute.

PUMP GEYSER
Temperature 199°F Interval steady. Duration steady. Height 2-3 feet. Pump Geyser, named for its descriptive sound, is a small, nearly constant geyser located in the center of Geyser Hill. It splashes, but only 2 to 3 feet high, and thumps without an apparent interval, though there are lulls. Since its discovery, this thermal feature has had no noticeable changes in activity. Even the 1959 earthquake had little effect on its function, though others around it were greatly affected. Since Pump is almost constantly in play it produces a steady flow of water which has resulted in a stable microbial community in the run-off channel. This is perhaps the richest and thickest laminated mat in the basin. It supports colonies of ephydrid flies, tiny, vermilion hot spring mites, and predator wolf spiders.

SPONGE GEYSER 
Temperature 199°F Interval 1 minute. Duration seconds to 1 minute. Height 1-2 feet. Sponge Geyser, named for its rounded, hole-ridden cone which gives it the appearance of a sponge, is the successor to an older, more active geyser. The iron-stained sinter cone is now in the process of erosion. It is one of the smallest geysers with most eruptions varying between six to nine inches and rare up wellings reaching two feet. The eruptions occur at one minute intervals and mainly consist of boiling. The water level drops and rises before another eruption.

GIANTESS GEYSER
Temperature 200.7°F Interval 0 to 41 eruptions per year (dormancy). Duration 3-43 hours. Height 150-200 feet. Nathaniel Langford of the 1870 Washburn Expedition named this feature "the Giantess, the largest of all the geysers we saw in eruption." Giantess is unpredictable with long dormant periods. When it does erupt, the first hour is generally the most spectacular. An eruption has two phases-a water and steam phase. Water periodically jets to 200 feet high during the first hour and as the water phase subsides steam begins and roars from the 15x20 foot crater, sending a large column of steam into the atmosphere. Giantess' vent has been probed to a depth of 62 feet below the lip. Subterranean connections exist between other Geyser Hill features and after an eruption, nearby Beehive Geyser may be triggered to erupt.

HEART SPRING
Temperature 201 °F Dimensions 8x13 feet. Depth 16 feet. This spring received its name because of the heart-like shape of the crater. Heart Spring has had temperature fluctuations from 150-202°F. This wide range of temperature has allowed microbial growth to form varicolored patterns. This spring is typical of many of Yellowstone's thermal springs. Nearly 10,000 thermal features exist in Yellowstone and many are alkaline hot springs similar to Heart Spring in size and appearance. One feature which distinguishes each is the bright, colorful cyanobacteria and algae which grow along the edge of run-off channels. Each spring has its unique pattern.

DEPRESSION GEYSER
Temperature 200°F Interval 3.5-5.5 hours. Duration 2-3 minutes. Height 8-10 feet. Prior to 1959 Depression Geyser was an unnamed spring and seldom erupted. It received its name because of the depressed appearance of the old sinter crater. The 1959 earthquake set this geyser into action and subsequent earthquakes have caused changes in its activity. An eruption is characterized by a strong overflow and a pulsating, splash-type eruption. Between eruptions the crater gradually fills with water colored a deep green. No underground connections are known to exist with other springs.

BEEHIVE GEYSER
Temperature 199°F Interval 7 hours to days (dormancy). Duration 4-5 minutes. Height 150-200 feet. The 1870 Washburn Expedition named this geyser after its beehive-shaped cone. The cone is three and a half feet high with a four foot diameter. Beehive, considered one of the largest active geysers in the world, erupts to a height of 200 feet. However, since its discovery, it has been unpredictable. It has eruptive intervals of eight to twelve hours, but it has infrequent eruptions as long as 3 to 10 days and dormancy of weeks to months. A small vent located a few feet east of Beehive, called Beehive's Indicator, erupts 6-10 feet usually 10-20 minutes before an eruption. An eruption begins with occasional splashing, then small surges. These progress into an eruption as the ground rumbles and a narrow, straight fountain of water jets upward.

PLUME GEYSER
Temperature 183-194°F Interval 25-36 minutes. Duration 1-2 minutes. Height 10-30 feet. Plume is an example of a newly formed geyser. It apparently formed as the result of a steam explosion in 1922, leaving a jagged opening flush to the ground. Plume flourished for several years, then became dormant until 1941 when it again became active and erupted nearly every hour on the hour. The 1959 earthquake changed its eruptive cycle and since then it has erupted on a half hour cycle with 1 to 4 bursts. In 1972 another steam explosion added and extended the vent to the west. An eruption is pending when water quickly rises in the crater and begins to overflow. The water pulses and splashing triggers an eruption. The geyser erupts at an angle directed to the west. The crater has been probed to a depth of 7.5 feet below the lip.

ANEMONE GEYSER
Temperature 200°F Interval 3-8 minutes, Duration seconds to 2 minutes, Height 3-10 feet.Turn-of-the-century tourists named this geyser after the anemone flower. The geyser erupts from two shallow basins, nearly six feet apart. The two vents, lined with sinter beads, act separately with minor eruptions occurring about every 5-10 minutes to a height of 5-6 feet. Activity shifts from vent to vent, but they seldom erupt together. This small geyser can be viewed from the boardwalk and easily demonstrates the workings of a geyser. Seconds before an eruption the throat emits a gurgling sound and the basin then fills with water. The pool begins splashing which triggers an eruption. After the eruption dies down the basin drains and emits a sucking sound as if a stopper were being pulled in a bath tub.

BLUE STAR SPRING
Temperature 192°F Dimensions 9x10 feet. Depth 6 feet. It received its name from the star-like sinter formation around the edge of the pool. Extensive ledges have formed three to four feet over the crater, creating an illusion of a small spring. The ornate scalloped border of the ledge also extends along the overflow channel. This spring has had a history of vandalism. In 1946 during cleaning, a pile of debris three feet in height by six feet in width was collected. A bison calf fell into the pool in the mid 1980s and the bones can still be seen on the bottom. No known subterranean connection exists with other thermal features. The spring discharges approximately four gallons per minute.

CHINAMAN SPRING
Temperature 200° Dimensions 28x34 inches. Depth 12.5 feet. A small spring located along the Firehole River. Chinaman has erupted 20-30 feet high, but all known eruptions were man-induced. The first incident of a known eruption occurred in the 1880s when a Chinese laundryman pitched his tent over the spring and used the hot water as a clothes boiler. The clothes were suspended in the boiling water by a wicker basket. When laundry soap was added the spring erupted for the first time and a column of water ejected the laundry and collapsed the tent.

LONE STAR GEYSER
Temperature 197° Interval 3 hours. Duration 30 minutes. Height 35-40 feet. The 1872 Hayden Expedition originally named this feature Solitary because it was an isolated geyser on the upper Firehole River. Its large, streaked sinter cone is 11.5 feet high. One large vent and several smaller apertures constantly splash during the quiet phase. This splashing is responsible for the cone growth. An eruption usually occurs in two phases. The first phase may be a short eruption lasting three to five minutes with jets reaching 25 feet. After a period of 15-25 minutes the second phase begins with splashing, then continues with a forceful jet of water which progresses into a steam phase. The second phase lasts 30 minutes.