West Thumb Geyser Basin - Yellowstone National Park

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West Thumb Geyser Basin - Yellowstone National Park

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Difficulty: Easy
Length: 0.7 miles / 1.1 km
Duration: 1 hour or less

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Looking Toward West Thumb of Yellowstone Lake

Overview: Lake Facts

Elevation: 7,733 ft (2,357 m)
Area: 131.7 sq mi (341 sq km)
Shoreline: 141 mi (227 km)
Width: 14 mi (23 km)
Length: 20 mi (32 km)
Avg depth: about 140 ft (42 m)
Max depth: 410 ft (125 m)
Avg summer temp: 45°F (70°C)

West Thumb Facts

West Thumb is a caldera within a larger caldera.
Active hydrothermal features exist on the lake bottom here and elsewhere in the lake.

West Thumb Geyser Basin overlooks Yellowstone Lake, the largest lake at high elevation in North America. You can best appreciate its vastness in winter when the frozen surface extends as a white sheet for miles. Summer is the season to appreciate the lake's many moods. Here you can enjoy its calm, quiet mornings or witness the wind-whipped whitecaps of afternoon storms. After storms, look for rainbows arching into the wilderness beyond, a land nearly as wild as when Native Americans and explorers experienced it centuries ago.

The surface of the lake hints of what exists below. Surveys of the lake bottom in the 1990s documented hot springs and hydrothermal vents just offshore in West Thumb. Look closely—you may see their swirling patterns in the water.

Framed on the east by the Absaroka Range, the lake may be thought of as the heart of Yellowstone. Its waters are the lifeblood for a large network of plant and animal communities. Trumpeter swans and moose thrive on the aquatic growth in shallow waters along the shore. Trout are drawn to zooplankton living in these waters. Cutthroat trout are food for pelicans, otters, eagles, black and grizzly bears, and other wild life. Unfortunately, this population of cutthroat trout is now threatened by non-native lake trout.

As you walk among the basin's superheated waters, you may wonder if the lake is warmer here than elsewhere. After all, the geyser basin pours an average of 3,100 gallons (11,733 liters) of hot water into the lake every day. But even here, the lake's average summer temperature is 45°F (7°C).

Explosive Encounter

The large circular bay of West Thumb is an excellent example of a volcanic caldera. A powerful volcanic explosion approximately 174,000 years ago caused the earth's crust to collapse, creating the West Thumb caldera. The depression produced by the volcano later filled with water to become this large bay of Yellowstone Lake.

The West Thumb caldera lies within an even greater caldera, the Yellowstone Caldera, which is one of the world's largest and encompasses the central and southern portions of the park. Much of your visit in Yellowstone may be spent within the boundaries of this huge caldera. This larger caldera, and the lava that eventually filled it, shaped much of the present Yellowstone landscape. It resulted from a massive eruption roughly 640,000 years ago. Since that time, numerous lava flows have filled the caldera.

A Bit of History

People have long been drawn to West Thumb. Native Americans favored campsites in this area as they hunted bison in the summer. The Crow people gathered medicinal herbs here. Shoshone and Bannock peoples have stories about the formation of the lake. Early scientific expeditions, which corroborated the tales of colorful hot springs mentioned by mountain men, rested here. Visitors in the late 1890s and early 1900s appreciated a refreshing boat ride to Lake Yellowstone Hotel after several dusty days on rutted roads. The rustic log cabin near the parking lot was the original West Thumb Ranger Station built in 1925; it is one of the few such stations remaining. Now it serves as a summer visitor information station and a winter warming hut.

Water Colors

The colors you see in the pools of West Thumb are created, in part, by thermophiles (heat-loving microorganisms). Generally, green and brown indicate organisms living in cooler water, orange and yellow indicate those living in hotter water. Only a few microorganisms thrive in the springs where the temperature is close to boiling, so we see the clear, blue water. In these hot springs, the water absorbs all wavelengths of light except blue, which the pool reflects.

Tips: Hydrothermal features are fragile rarities of nature. Yellowstone preserves the largest collection of hydrothermal features on the planet. You have an unparalleled opportunity to view hot springs, geysers, mudpots, and fumaroles in a natural setting.

Change takes place naturally in a hydrothermal area, but people can disrupt these processes and cause irreparable damage. Rocks, sticks, and other objects thrown into a hydrothermal feature may be permanently cemented in place, choking off water circulation and ending all activity.

For the sake of all who follow, never throw objects into any feature. Stay on established walkways for your safety and to protect fragile formations that have formed over thousands of years.

It is illegal to collect any natural or cultural objects or to remove, deface, or destroy any plant, animal, or mineral in Yellowstone's hydrothermal areas. Bring drinking water; take out all trash.

While viewing or photographing the area, protect your camera, glasses, and binocular lenses from hydrothermal heat and stray.

Toxic gases exist in Yellowstone. Dangerous levels of hydrogen sulfide and carbon dioxide have been measured in some hydrothermal areas. If you feel sick, leave the location immediately.

Help preserve Yellowstone for the future.

Points of Interest

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Fumaroles

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Twin Geysers

Twin Geysers—one geyser with two vents—has short periods of dramatic eruptions and extended periods of dormancy. After a 23-year dormancy, it began erupting again in 1998; its last known eruption was in 1999. Visitors lucky enough to witness an eruption see a two-part event. The west vent erupts 70 feet (21 meters), then the east vent erupts more than 100 feet (30 meters).

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Abyss Pool

One of the deeper hot springs in the park, Abyss Pool descends to 53 feet (16 meters). It varies from turquoise blue to emerald green to various shades of brown. In 1883, a park visitor described it as "a great, pure, sparkling sapphire rippling with heat."

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Black Pool

Not long ago, Black Pool really was black. Lower water temperature allowed thick mats of dark green and brown thermophiles (heat-loving microorganisms) to grow in the pool, causing it to appear black. The water temperature rose during the summer of 1991, killing these organisms. Black Pool also erupted that summer and several times the following winter. Like Abyss, Black Pool is now one of Yellowstone's most beautiful pools.

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Big Cone

Jutting out into Lake Yellowstone, Big Cone, a companion to Fishing Cone, is a large sinter cone, and is sometimes seen completely submerged by the lake. Eruptions from this geyser are rare, and only reach heights of one foot or less.

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Fishing Cone

Mountain men told of a geyser on the shore of a high alpine lake where one could catch a trout, swing the pole around, dip it into the boiling pool, and cook the fish without taking it off the line. This cooking-on-the-hook feat at Fishing Cone became famous after it was described by a member of the 1870 Washburn Expedition. Visitors often dressed in a cook's hat and apron to have their picture taken at the "Chowder Pot" or the "Fish Pot." Anglers often injured themselves while straddling the boiling water, and their feet damaged the geyser's cone. Fishing is no longer allowed from Fishing Cone.

DSC_4316.JPG (West Thumb, Wyoming, United States) Photo

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Lakeshore Geyser

Accounts from the 1920s and 1930s tell of Lakeshore Geyser erupting up to 50 feet (15 meters). The smaller of the two geyser vents is generally not exposed until mid to late August. Although Lakeshore Geyser boils vigorously and almost continuously, and often erupts a few feet, its last known major eruption was in 1970. One day, however, earthquake activity or other processes may cause the geyser to gain energy and begin erupting more forcefully again.

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Lakeside Spring

Lakeside Spring's blue-green pool of thermal water drains into Yellowstone Lake. The colors you see in the pools of West Thumb are created, in part, by what grows in these hot waters. Thermophiles (heat-loving microorganisms) have different colors and different temperature requirements. Generally, green and brown indicate organisms living in cooler water, orange and yellow indicate those living in hotter water.

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Seismograph and Bluebell Pools

These pools used to be known as the "Blue Pools." After the 1959 Hebgen Lake earthquake, which measured 7.5 on the Richter scale, the pools were renamed. At West Thumb, no one recorded the nature of the changes caused by the quake, but perhaps someone thought Seismograph Pool somehow "registered" the earthquakes. (A seismograph measures the intensity and time of earthquakes). These days, Seismograph is sometimes muddy—but not from earthquakes. The mud comes from the runoff of nearby mud pots.

DSC_4310.JPG (West Thumb, Wyoming, United States) Photo

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Thumb Paint Pots

Known today as the Thumb Paint Pots, the Hayden Expedition of 1871 originally named these fanciful features the "Mud Puffs." Picture a field of miniature mud volcanoes that are 3 to 4 feet (1 meter) high with steam curling from their delicate mud chimneys in various shades of red. Surrounding the cones, the mud appears to be stirred and mixed to the smoothest, most satiny consistency by some unseen hand. Mud pots vary with precipitation and groundwater levels. Sometimes they look like muddy water; other times they look as if you could build pottery with their mud.

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Surging Spring

Surging Spring is true to its name. With an average temperature of 167 degrees Farenheit (75 degrees Celsius), it domes up and overflows, sending waves of water surging into the lake.

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Collapsing Pool

Collapsing Pool, for obvious reasons, was also named for its appearance. Like Ledge Spring, this pool can sometimes be seen full and blue, or colorful and half empty.

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Ledge Spring

Named for its appearance, Ledge Spring fluctuates from hot, blue, and overflowing to cool, colorful, and half empty.

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Percolating Spring

When it was named, Percolating Spring bubbled vigorously like a coffee pot.

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Thumb Geyser

Thumb Geyser is now totally inactive and lies covered by the cool runoff of other springs like these in the middle of the geyser basin. "Dynamic" describes any geyser basin, but particularly the central area of West Thumb. These features are constantly in flux, changing from season to season—even month to month.

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Perforated Pool

Perforated Pool is one of a group of hot springs in the middle area of the basin that all seem to share a common plumbing system. When major features, such as Abyss and Black pools, are in an active phase, this secondary cluster can be drained of water.

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Ephedra Spring

Ephedra Spring, like many of the hot springs in the Central Basin of West Thumb, can vary dramatically in appearance depending on how hot or cool it is, and how much water it contains.

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Blue Funnel Spring

Blue Funnel Spring was long known for the distinctive ring of color around its perimeter. However, when Abyss pool began erupting during the winter of 1991-92, the water in Blue Funnel, and in adjacent Perforated Pool and Ephedra Spring, cooled and sank well below the rim. Then the four features appeared to exchange energy: Abyss stopped erupting at the end of that winter, while these features were rejuvenated.

Pictures in this guide taken by: burnsdye, rochejaune, ysato_JAPAN, gluecklichinkassel

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