Norris Geyser Basin, named after an early Yellow-stone Superintendent, may be the hottest geyser basin in Yellowstone. The Carnegie Institute of Washington, D.C. made test wells in 1929 to determine subsurface temperatures. One test hole was abandoned at 265 feet when the temperature reached 401 °F and the steam pressure threatened to destroy the drilling rig.

The stark, barren landscape of Porcelain Basin is the result of an acidic environment. Because of this hostile condition plants, algae and bacteria have difficulty in establishing themselves. Instead the basin derives its colors from mineral oxides, in spectrums of pink, red, orange (iron oxides) and yellow (sulfur and iron sulfates). The acidic water has also created changes in the formation of sinter deposited around vents. Silica deposits as tiny, sharp spines instead of thick, beaded deposits common in more alkaline basins.

The largest geyser in the world is located here. Steamboat Geyser has long periods of dormancy, but when it does erupt it sends jets of water nearly 380 feet high in a spectacular display.

ROARING MOUNTAIN
Temperature 198°F Geologists Arnold Hague and Walter Weed named this thermal feature in 1885. Hague stated "it takes its name from the shrill, penetrating sound of the steam constantly escaping from one or more vents located near the summit, and on a calm day, or with a favorable wind, the rushing of the steam through the narrow orifices can be distinctly heard." Roaring Mountain, located 4.5 miles north of Norris Geyser Basin, is a barren, furrowed, white ridge, rising 400 feet from the base. The mountain side is spotted with steam vents or fumaroles, and the fumaroles' vents are rimed with bright yellow, crystalline sulfur deposits. The leaching of sulfuric acid has produced the stark, barren environment.

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CINDER POOL
Temperature 196-198°F Dimensions 30 feet diameter. Depth 38 feet. Cinder Pool, once called Verma Spring, is a remote and isolated feature on the One hundred spring Plain. No trail leads to the spring and it is difficult to find. The spring is flush to the ground, with milky water and a clay edge. It is a very fragile and dangerous feature and extreme caution should be taken when approaching it. The spring boils and water pulses, but there is no visible outlet. The water is high in chloride and sulfate. On its surface, pushed to the edges, are small-BB to pea size-black, hollow sulfur beads, which are extremely fragile. No one yet knows exactly how the floating beads form. The beads are composed of sulfur, quartz, feldspar and obsidian rhyolite. When dried they bum freely.

VALENTINE GEYSER
Temperature 197°F Interval irregular (5-50 hours) to dormancy. Duration 60-90 minutes. Height 20-75 feet. Valentine geyser erupted for the first recorded time on February 14,1907 from a spring called Alcove. C.W. Bronson renamed this geyser to commemorate its birth. This geyser is very irregular, having seasons or years of dormancy. It erupts from a six-feet-high cone, located in a deep, wide alcove. The major activity of an eruption lasts only five to seven minutes jetting water up to 75 feet, but usually eruptions are around 25 feet. A steam phase follows which lasts up to 90 minutes but gradually diminishes in height. It is a quiet eruption, unlike other Norris thermal features.

LEDGE GEYSER
Temperature 199°F Interval rare to dormancy. Duration 20 minutes to 2 hours. Height 75-125 feet. J.E. Haynes named this feature in 1927 because of its position under a ledge of geyserite. It is the largest geyser in Porcelain Basin, but it is very irregular with periods of dormancy. It has been inactive since the mid 1970s, but new, boiling, active springs have sprouted below Ledge Geyser. When it is active it erupts from five vents. Before an eruption one of the small vents fills with water, splashing begins and progresses into a powerful burst of water. The main jet arches at a 40° angle and jets out 125 feet. The other vents may also play for up to 30 or 60 feet high. The main eruption lasts 20 minutes and slowly subsides after two hours. There is a rushing sound which accompanies each eruption, and the steam phase roars and rumbles.

PORCELAIN TERRACE SPRINGS
Temperature 203°F This area of Porcelain Basin is stark and barren, nearly void of plant life. Acidic and low alkaline water is responsible for creating this unique environment. Sulfur brought to the surface oxidizes to form sulfuric acid, creating an acidic environment hostile to plant life. The springs have deposited a thin layer of porcelain-like silica, stained yellow and orange by sulfur and iron oxides. The crust is fragile and new springs are constantly forming and breaking through. Old vents from extinct springs become drains for new springs and are quickly sealed over by new deposits.

AFRICA GEYSER
Temperature 120°F Interval 90 minutes. Duration minutes to constant. Height 45 feet. Africa Geyser began erupting in February 1971. It was formerly a spring in the shape of the African continent. Africa Geyser is an example of the life and death of a geyser. When it first evolved, eruptions were very regular, at nearly 90-minute intervals with plumes 45 feet high. Beginning in 1973 it was still active, discharging mostly a mixture of water and steam until Africa declined and went into dormancy. Presently, there is no indication, other than a small vent, that a geyser ever existed. Nevertheless, a disturbance or shifting thermal activity could form a new feature nearby.

WHIRLIGIG GEYSER
Temperature 190°F Interval minutes to hours. Duration 2-4 minutes. Height 10-15 feet. The Hague Party in 1904 named this feature for its whirling, puffing eruption. There are periods of dormancy during which a related geyser, called Little Whirligig Geyser, may become active; currently the smaller geyser is inactive. Whirligig Geyser begins an-eruption cycle with a sudden filling of the crater progressing into an eruption. Most activity occurs from the central vent where an angled plume sprays at periodic bursts. Like many of Morris' geysers there is a roaring, hissing sound accompanying an eruption. There are subterranean connections between Constant, Little Whirligig and Whirligig geysers.

STEAMBOAT GEYSER  
Temperature 198°F Interval days to periodic dormancy. Duration minutes-hours. Height 100-380 feet. Originally named by the 1878 Hayden Expedition for its steamboat-like spouting. There have been name changes to Fissure and New Crater geyser, but Steamboat is the preferred name. Steamboat is the world's tallest geyser. Even though it has periods of dormancy, some lasting decades, it is a spectacular geyser when it does erupt. Eruptions are difficult to predict. Before an eruption, splashing begins within the cone, building into an eruption which may spout up to 380 feet. However if there is activity it is usually only splashing or minor displays which can reach only up to 10-60 feet high. Because of the large amount of water needed for an eruption, there may be subterranean connections which tap into other thermal springs.

CISTERN SPRING
Temperature 194.1°F Dimensions 27x41 feet. Depth 31 feet. In 1966 Cistern Spring transformed from a small, gray pool to a large, colorful pool with terraces. The increased overflow engulfed trees and rapidly deposited a sinter terrace. Since 1966 the terrace has grown at an average rate of 1.5 inches a year. When Steamboat Geyser has a major eruption the water in Cistern nearly empties. After an eruption of Steamboat, Cistern Spring requires one to three days to replenish. As a water reservoir for Steamboat Geyser, it has an appropriate name. Brightly colored cyanobacteria distinguish the rounded terraces of this spring.

ECHINUS GEYSER  
Temperature 196°F Interval 30 minutes to 2 hours. Duration 3-15 minutes. Height 50-100 feet. The sinter, spine-covered crater reminded early visitors of the spiny sea urchin. Echinus derives from the Greek word for spiny. A light red-brown iron oxide deposited with silica colors this crater. It is the largest predictable geyser at Norris Geyser Basin. Before an eruption, water usually fills the basin to within two or three feet of the rim and begins boiling. Churning and splashing then trigger an eruption throwing water and steam upward in a series of explosive bursts. After an eruption the basin drains producing a whirlpool and a gurgling which sounds as if the stopper from a bath tub had been pulled.

VIXEN GEYSER  
Temperature 195°F Interval minutes to hours. Duration seconds to 50 minutes. Height 5-30 feet. Superintendent P.W. Norris named this small geyser located along the trail of the Back Basin for its temperamental, spitfire disposition. It has a pink-colored vent stained by iron oxides deposited with silica. The geyser erupts from a round, cylindrical vent. Vixen has had two types of eruptions. One is minor activity every few seconds with occasional splashing and spouting up to 15 feet high. A major eruption will last up to an hour with water jetting to 30 feet, but these are rare and unpredictable. After an eruption the crater drains and produces gurgling sounds.

PORKCHOP GEYSER
Temperature 98-162°F Dimensions 13x18 feet. Depth 2.5 feet. Porkchop is a relatively new and still changing feature in the Back Basin. Geologist Don White named this feature in 1961 for its porkchop-shaped crater. Until 1985 Porkchop remained a quiet, but erratic geyser, with occasional eruptions 15-20 feet high. In 1985 it began to erupt continuously, spouting 30 feet high from a 3-inch diameter vent. The geyser was unusual because the temperature was below boiling, around 100°F, and the water was heavily laden with silica. During the winters the cool spray from the continuous eruption built large ice cones nearly 8 feet high, which were draped with a translucent silica gel. On September 5, 1989, in view of visitors, Porkchop exploded, sending rock and debris 100 to 220 feet away. Now only a bubbling, seething pool remains.