Norris Geyser Basin is the hottest and most changeable thermal area in Yellowstone.    It is the location of the tallest active geyser, colorful hot springs, and microscopic life in one of the most extreme environments on earth.  Rainbow Colors, hissing steam, and pungent odors combine to create an experience unique in Yellowstone.  Porcelain Basin is open terrain with hundreds of densely packed geothermal features; in contrast, Back Basin is forested and its features are more scattered and isolated.  The Norris Geyser Basin is made up of two major parts: the Porcelain Basin and the Back Basin.

Porcelain Basin: This basin consists of a whitish rock-sheet that pulsates from the pressure of steam and boiling water beneath it.  A number of its geysers and other features have been born suddenly in small hydrothermal explosions.  Some features are ephemeral, their activity lasting a few hours, days, or even weeks.

The hottest of Yellowstone's geothermal features are steam vents (fumaroles).  Black Growler Steam Vent, on the hillside in front of you, has measured 199 to 280 degrees F (93 to 138 degrees C).  A plentiful water supply would help cool these features; however, steam vents are usually found on hillsides or higher ground, above the basin's water supply.  They rapidly boil away what little water they contain, releasing steam and other gases forcefully from underground.

Ledge is the second largest geyser in the Norris Geyser Basin, capable of shooting water125 feet into the air. Because it erupts at an angle, however, the water will sometimes reach the ground 220 feet away. It has at times in the past erupted at regular intervals of 14 hours. The geyser became inactive between 1979 and late 1993.   It erupted on a fairly regular cycle of every four to six days in 1994 and 1995.

A visit most times of the year will show a Congress Pool that appears pale blue in color as picture on the left.  Due to the variable nature of Norris features it  is possible to see the same pool looking muddy and boiling violently as pictured below.  At Norris, "disturbances" of geothermal activity take place annually.  No other thermal area in Yellowstone exhibits this phenomenon.  Mysteriously features throughout the Norris area undergo dramatic behavioral changes literally overnight.  Clear pools become muddy and boil violently, and some temporarily become geysers. These "disturbances" often occur in late summer and early fall but have been observed throughout the year.  Features that typically behave as geysers may display altered eruption cycles or temporarily cease erupting.  New features may be created during a disturbance, although they seldom remain long-term attractions at the basin.  Disturbances tend to last from a few days to more than a week.  Gradually, most features revert to "normal" activity.  Why this happens is not fully understood.  Further study will no doubt yield new clues that will help unravel the mystery of this phenomenon and lead to a greater understanding of the earth's hidden geologic forces.

The milky color of the mineral deposited here inspired the naming of Porcelain Basin.  The mineral, siliceous sinter, is brought to the surface by hot water and forms a sinter "sheet" over this flat area as the water flows across the ground and the mineral settles out.   This is the fastest changing area in Norris Geyser Basin, and siliceous sinter is one of the agents of change.  If the mineral  seals off a hot spring or geyser by accumulating in its vent, the hot, pressurized water may flow underground to another weak area and blow through it.  Siliceous sinter is also called geyserite.   Deposits usually accumulate very slowly, less than one inch (2.5cm) per century, and form the geyser cones and mounds seen in most geyser basins.

 Little Whirligig Geyser was named because of its close proximity to Whirligig Geyser. Whirligig was so named because while erupting its water swirls in its crater. The orange-yellow iron oxide deposits around Little Whirligig make it one of the most colorful features in Porcelain Basin.  It has been dormant for several years.

There are also other geothermal features in the Porcelain Basin of Norris Geyser Basin.  They are all different and definitely worth seeing.

Back Basin:

A hot spring's color often indicates the presence of minerals.  In a clear blue pool, the water is absorbing all colors of sunlight except one, blue, which is reflected back to our eyes.  Here in Emerald Spring's pool, another factor joins with light refraction to give this spring its color.  The 27-foot (8 meter) deep pool is lined with yellow sulfur deposits.  The yellow color from the sulfur combines with the reflected blue light, making the hot spring appear a magnificent emerald green.  Hot spring water can dissolve and transport sulfur from underground.  The mineral can deposit and crystallize at the earth's surface, sometimes in hot spring pools.

The world's tallest active geyser, Steamboat can erupt to more than 300 feet (90m), showering viewers with its mineral-rich waters.  For hours following its rare 3 to 40 minute major eruptions, Steamboat thunders with powerful jets of steam.  As befitting such an awesome event, full eruptions are entirely unpredictable.  Recently, Steamboat had one major eruption on May 2, 2000.  More commonly, Steamboat  has minor eruptions and ejects water in frequent bursts of 10 to 40 feet.

Cistern Spring and Steamboat Geyser are linked underground.  During a major eruption of Steamboat, the water in Cistern Spring's pool drains.  Normally Cistern is a beautiful blue pool from which water continually overflows.  It is quite creative, depositing as much as 1/2 inch (12mm) of grayish sinter each year. By comparison Old Faithful Geyser and many other thermal features may build at the rate of 1/2 to 1 inch (12 - 25mm) per century.  Cistern Spring's influence expands throughout the lodgepole pine forest below.  This forest has been slowly flooded with silica rich water since 1965.  The pioneering lodgepole pine forest at Norris is in constant flux, retreating here and in other areas of increasing heat while advancing in places of diminished thermal activity.

Porkchop Geyser before eruption.

Dramatic behavioral changes have characterized Porkchop Geyser during the last decade. Once a small hot spring that occasionally erupted, Porkchop Geyser became a continuous spouter in the spring of 1985. The force of the spray caused a roar that could be heard at the museum over 660 yards (603m) away. On September 5, 1989, Porkchop Geyser exploded. Rocks surrounding the old vent were upended and some were thrown more than 216 feet (66m) from the feature. Porkchop Geyser is now a gently rolling hot spring.

Porkchop Geyser after eruption.

Norris Geyser Basin offers great diversity in thermal features largely because it is at the junction of several disturbances in the earth's crust.   A major fault (rock fracture) runs south from the Mammoth Hot Springs area toward Norris.  This fault crosses another fault extending eastward from Hebgen Lake to Norris.  Both of these breaks in the earth's surface intersect with fractures radiating from the great caldera that dominates central Yellowstone.  Water from rain and snowfall percolates downward through cracks and fissures and becomes heated, rising to the surface again as a hot spring, geyser, mud pot, or steam vent.  At Norris, a rare combination of ingredients creates a landscape unique on this planet.

*Information on this page provided by the NPS.