West Thumb Geyser Basin
The West Thumb Geyser Basin is a unique thermal area lying right on the shore of Yellowstone Lake. To reach it, drive 0.2 miles north of the West Thumb Junction, or 20.8 miles southwest of Fishing Bridge Junction on the Fishing Bridge to West Thumb section of the Grand Loop Road.
Blue Funnel Spring
A single path leaves the parking area and arrives at a T intersection. Head left, passing an area of fumaroles, and then turn right on the inner boardwalk. The first feature is the Blue Funnel Spring, a very hot, light blue spring.
The next pool is Ephedra Spring, another hot and blue hot spring.
The next in this series of springs is Perforated Pool.
Thumb Paint Pots
The boardwalk passes a few more pools and arrives at the Thumb Paint Pots area. These features are formed when the waters of a spring are more acidic than normal. They dissolve the plumbing of the hot spring and result in a watery mud pool.
The boardwalk arrives at another T intersection. Turn left to visit the back section of the basin. Bluebell Pool is on a short side path to the right.
The boardwalk follows along the shore of Yellowstone Lake, passing some lakeside geyser features. The most known of these is Fishing Cone. At present, none of these is actively erupting.
Just as the boardwalk leaves Yellowstone Lake’s shore is Black Pool, on the left. This pool used to be black from all of the bacteria mats underneath. However, the water temperature rose dramatically in 1991. Now it is a stunning clear and deep blue pool.
The last major feature of this area is Abyss Pool, one of the deepest pools in the park. It descends to a depth of 53 feet. This pool erupted to heights of 100 feet in the 1990s, but has since been quiet.