West Thumb Geyser Basin

Click on image for larger version. Courtesy Yellowstone Association/NPS

West Thumb Geyser Basin

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, though 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, then the east vent erupts more than 100 feet.

Abyss Pool:  One of the deepest hot springs in the park, Abyss Pool descends to 53 feet.  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.”   Abyss Pool erupted for the first time in recent history in August of 1987.  It remained quiet again until September 1991, when it erupted frequently in spectacular, but short 100 foot bursts.  The next active period lasted from December 1991 through June 1992, when it erupted several times per day.  The pool’s entire body of water appeared to turn end-over-end in a turbulent boil.  Since that time, Abyss has been a quiet, distinctive feature at West Thumb.

Black Pool:  At one time, Black Pool really was black.  Lower water temperatures allowed thick mats of dark and brown thermophiles to grow in the pool, causing it to appear black.  The water temperature rose during the summer of 1991, killing the organisms.  Black Pool also erupted that summer and several times the following winter.  Black Pool is now a quiet and beautiful pool.

Fishing Cone:  Mountain men told of a geyser along an 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.  Visitors are sometimes surprised to find Fishing Cone under water.  During the spring and early summer, lake levels rise from the melting snow and cover the vent.  When exposed the temperature of the cone’s water averages just above boiling point (199 degrees F at this altitude).

Lakeshore Geyser:   Although Lakeshore 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.

Seismograph & Bluebell:  These pools used to be known as the “Blue Pools.”  After the 1959 earthquake, which measured 7.5 on the Richter Scale, the pools were renamed.  Seismograph Pool was named after naturalists noticed that slight earth tremors supposedly caused the water to become turgid and to increase in temperature.  The truth is that the pool becomes muddy from runoff from nearby mudpots, not seismic activity.

Thumb Paint Pots:  The Hayden Expedition of 1871 originally named these features the “Mud Puffs.”  Resembling a field of miniature volcanoes 3-4 feet high with steam curling from delicate mud chimneys in various shades of red.  Surrounding the cones, the mud appears to be stirred and mixed to a smooth, satiny consistency by some unseen hand.  Sometimes the mud was thrown 25 feet.  Beginning in the 1970s, the Paint Pots became less active, but recently activity has begun to increase again.

The Central Basin:  Surging Spring is true to its name.  With an average temperature of 167 F, it domes up and overflows, sending waves of water into the Lake.  Ledge Spring and Collapsing Pool fluctuate from hot, blue, and overflowing to cool, colorful, and half empty.  When it was named, Percolating Spring bubbled vigorously like a coffee pot.  Blue Funnel Spring was long known for the distinctive color around its perimeter.  When Abyss Pool began erupting during the winter of 1991/92, the water in Blue Funnel, Perforated Pool, and Ephedra Spring cooled and sank below the rim.  Then the four features appeared to exchange energy: Abyss stopped erupting at the end of that winter, while the other three rejuvenated.

SOURCESYellowstone Association Trail Guide, April, 2009. Yellowstone Place Names, 2006 (Lee Whittlesey)