Fountain Paint Pot - Yellowstone National Park

Thermophiles (heat-loving microorganisms such as bacteria) usually form the ribbons of color like you see here. The green, brown, and orange colors are mostly cyanobacteria, which can live in waters as hot as 167°F (75°C). At this temperature they are usually yellow-green. As water cools, different varieties of cyanobacteria appear in shades of orange, rust, or brown. Color may also change with the seasons and sunlight levels.

At Silex Spring, consider how this hot water arrived at the surface. Deep beneath your feet, heat from partially molten rock beneath the surface is transmitted up through the earth's crust. Ground water circulating through these rocks becomes heated and follows cracks upward. Where the hot water can escape at the surface, a hot spring forms.

Silex is Latin for silica, the major component of rhyolite, the primary volcanic rock in Yellowstone. Hot water dissolves silica, which precipitates as siliceous sinter along the bottom of the spring and in runoff channels.

Thermophiles thrive in the overflow of Silex Spring. They provide food for flies living in and on the hot water. The flies then become food for mites, spiders, insects, and birds.

Mats and flies don't exist in the pool or at the start of the overflow where the water is too hot (167-199°F; 75-93°C) for most thermophiles.

The activity of Silex Spring, like that of other hydrothermal features, can change. For example, after 21 years of dormancy, Silex Spring erupted many times from 2000 to 2006.

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.

At Fountain Paint Pot, what you see varies with the season. In early summer the mudpots are thin and watery from abundant rain and snow. By late summer they are quite thick. If the mud is thick today, watch out! Bursting bubbles may lob mud over the rail.

The mud is composed of clay minerals and fine particles of silica. In this area the rock is rhyolite, which is composed primarily of quartz and feldspar. Acids in the steam and water break down the feldspar into a clay mineral called kaolinite. The Crow tribe used to paint their tipis with this mud.

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.

The hiss and roar of a fumarole comes from gases—steam, carbon dioxide, and a little hydrogen sulfide—rushing from the earth through a vent. A fumarole's channel system reaches down into the hot rock masses, but it contains very little water. When water contacts the hot rock, it flashes into steam, which increases its volume 1500 times and drives the gases from the vent.

Red Spouter, which originated with the Hebgen Lake Earthquake, exhibits the behavior of all four thermal features. In the spring and early summer it is a muddy hot spring that may seem like a geyser as it splashes reddish water several feet high. As the water table lowers in late summer and fall, Red Spouter seems more like a big mudpot, and then a hissing fumarole.

Leather Pool underwent dramatic changes after the Hebgen Lake Earthquake of 1959. Prior to the earthquake, it was a warm (143°F/62°C) pool that supported leather-like thermophilic brown bacteria. After the earthquake, water temperatures rose to boiling and killed the microorganisms. Since that time, Leather Pool has cooled and again supports the brown bacteria.

Distant hills and mountains comprise a volcanic tableland, described later.

Before you descend the stairs, walk out to the viewpoint on your left to view the geysers below. From this overlook you might see half a dozen geysers erupting at the same time.

Yellowstone is one of the few places in the world where geysers occur. The essentials for geysers and hot springs exist here. Snow and rain provide water, heat from deep in the earth warms the rock and water above it, and fractures in the rock provide the "plumbing" through which the water circulates.

A geyser's channels have constrictions that prevent the water from circulating freely to the surface where the heat would escape. Pressure builds. Steam rises and is trapped by the constrictions and overlying cooler water. At a critical point the confined steam actually lifts the cooler water and causes the geyser to overflow or splash. Pressure release continues, more steam rises and forces water out of the vent. The eruption begins.

Twig Geyser is the first regularly erupting geyser on this trail. Look for it at the base of the steps on the right. Twig erupts in a series of brief eruptions 2-10 feet (0.6-3 m) high.

On your left, Jet Geyser may erupt before an eruption from Fountain Geyser. During its active period, Jet erupts every few minutes up to 20 feet (6 m).

Across from Jet, Fountain Geyser may appear empty before an eruption. When it does erupt, it is one of the most impressive geysers in the park. Eruptions reach 20-50 feet (6-15 m) and last 25 minutes or more.

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.

Behind Fountain, you can see the pool for Morning Geyser, which seldom erupts. Should you be so lucky, you will see one of the park's largest geysers. Morning's eruptions have been high (80-200 feet/25-61 m) and wide (100 feet/31 m).

Before 2006, Spasm Geyser erupted for an hour or more until Fountain erupted but now its eruptions are shorter and more frequent. Spasm's eruptions may start with bursts up to 20 feet (6 m), then splashes about 3 feet (0.9 m) high.

You will probably see Clepsydra Geyser erupting. This nearly constant performer splashes from several vents and its steam can be seen throughout the Lower Geyser Basin. Its name is Greek for "water clock," and was given because the geyser used to erupt every three minutes. Since the 1959 Hebgen Lake Earthquake, Clepsydra erupts almost without pause. Sometimes it stops near the end of or after Fountain's eruption.

Below Clepsydra you can see the vast amount of sinter deposited in this area. Sinter was first deposited by hydrothermal activity in the Firehole Valley as glacial ice retreated. It continues to accumulate at different rates depending on the water chemistry of each spring and the rate at which it erodes. The sinter mound beneath these geysers has been building for thousands of years.

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.

Temperature 196.7°F 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.

Dead lodgepole pine trees in the geyser basin are pioneers that did not survive. Establishing a toehold in thin new soil, the trees enriched the soil through natural recycling of minerals and organic material. In time the increasing humus would have nurtured a mature forest- if the trees hadn't drowned when nearby hot springs shifted. Silica also penetrated the trees and hardened their bases. Perhaps lodgepoles will one day grow again in this area. Notice the grasses and other plants starting the cycle.

Celestine Spring is the last hot spring on this trail. No documentation exists of how this spring was named—but its blue color does seem to match the deep blue of the sky.