West Yellowstone 

West Yellowstone includes the Lower, Midway and Upper Geyser Basins , all of which are situated along the aptly named Firehole River.  This region contains the majority of the world's active geysers and Upper Geyser Basin has the highest concentration in the world. As well as geysers, three other hydrothermal features exist here: mudpots, fumaroles and colourful hot springs.

Lower Geyser Basin

The geysers of Lower Geyser Basin.

Clepsydra Geyser erupts almost constantly from several vents - its steam can be seen from almost anywhere in the basin.

Clepsydra Geyser

Colours of Clepsydra.

Midway Geyser Basin

Hot water overflowing from hot springs runs into the Firehole River.

Hot water flows from Grand Prismatic Spring providing an environment for Thermophiles as it cools.  Thermophiles are heat-loving micro-organisms, like bacteria, which can survive in water up to 75ºC (167ºF) and form ribbons of colour and bacterial mats in a variety of colours from orange to rust through to brown.

Orange and rust toned thermophilic algae thrive in the waters flowing from the Grand Prismatic Spring.

Ribbons of thermophiles and bacterial mat.

Colours of Grand Prismatic Spring.

Upper Geyser Basin

Old Faithful, a true American 'icon', hurls up to 8,500 gallons of boiling water into the air to heights reaching 184 ft. A 'fountain' type geyser, its eruptions can last 5 minutes or more, followed by a steam phase. Old Faithful puts on this spectacular display approximately every 90 minutes or so and is reputed to be every bit as good as it was in the 19th Century.

Old Faithful in its steam phase, nearing the end of an eruption.

Castle Geyser is a 'cone' type geyser. Its cone is formed from sinter and is one of the largest of its type in the world, it is also thousands of years old.  It erupts every 14 hours or so and water can reach heights of up to 75ft during its 20 minute long eruption. This is followed by a steam phase which may last up to 40 minutes.

Castle Geyser in its steam phase, with a rainbow.

Grand Geyser lives up to its name and hurls boiling water upwards at heights
often in excess of 200ft.  A classic fountain type, Grand Geyser often erupts in up to four bursts and can last as long as 12 minutes.

Beauty Pool's water is cooler where it is shallowest, providing habitat for the brown and orange toned thermophiles.

Chromatic Pool is hotest where the water is blue. Beauty Pool and Chromatic are related and lie next to each other.

Morning Glory Pool was named because of its likeness to the American wildflower, but that was in 1888 when its waters must have been much hotter and its colours more blue. In recent years it has cooled due to debris (such as coins, sticks and stones) being thrown into the water, these objects became embedded in the sides and vents restricting the flow of water. The brown and yellow bacteria are an indication of cooler water.
Lion Hill

Colorful run off from Chromatic Pool

Black Sands Basin

Morning on the Firehole River

Trees in Mist, Firehole River Valley

Antelope Flats Geysers

Great Fountain Geyser

Old Faithfull

Old Faithful erupts against a darkening sky.

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