Biscuit Basin is a group of geysers and pools in Yellowstone National Park’s Upper Geyser Basin. This section of the UNESCO World Heritage listed park has a loop trail around the main features of the group. At the end of the loop is another trail that leads to Mystic Falls and an overlook. This entry focuses on just a few of the geysers and pools in the Biscuit Basin.
The first features I encountered were Black Opal Pool, Black Diamond Pool, and Wall Pool. Black Opal Pool is the pool to the east. It has very rare but powerful eruptions and was formed by one in 1925. Black Diamond Pool is the central pool, formed by an explosion in 1918. Wall Pool is the oldest pool and the one to the west. It was formed between 1902 and 1911 but its origins are unknown.
Around the Boardwalk
The land the boardwalk passes over around these pools is like something out of an alien landscape. Deep reds, browns, and oranges make up the majority of the colors.
Next is Sapphire Pool, named for its brilliant clear blue water. The water in the pool is a very hot 202°F but was once cooler and calmer. A 1959 earthquake doubled the size of the pool and caused it to erupt as a geyser roughly every two hours, shooting water 150 feet into the air. In 1968, the geyser stopped functioning and it became a pool again. The runoff from the pool creates a stunning stream of yellow bacteria that flows under the boardwalk as you approach the pool.
After Sapphire Pool, the boardwalk turns into a loop. Staying to the left in a clockwise motion, the first geyser on the loop is the fun-to-watch Jewel Geyser. It’s the star of the Biscuit Basin, erupting every five to ten minutes at a height of up to 30 feet. Eruptions last 60 to 90 seconds. Its original name was Soda Geyser.
Further up to the left is Shell Geyser. It’s shape has the appearance of a shell. Eruptions are irregular and last between 20 and 90 seconds. Water can reach heights of up to eight feet. Later is Silver Globe Geyser and behind it Silver Globe Cave Geyser.
Continuing around the path at the junction of the offshoot to Mystic Falls is Avoca Spring. It was originally a spring but has been a regular geyser since the 1959 earthquake. It shoots water 10 to 20 feet high in eruptions that last about 20 to 30 seconds. Eruptions occur every one to 18 minutes.
Walking a bit along the extension to Mystic Falls is West Geyser, which has extremely rare eruptions.
The Mustard Springs
Back along the main loop are East and West Mustard Springs, separated by 50 feet. West Mustard Spring is just a spring while East Mustard Spring is a geyser, but in the past their roles were reversed. East Mustard Spring erupts every five to ten minutes for about five minutes at a height of up to six feet.
Coral and Black Pearl Geysers
The last two geysers around the loop are Coral Geyser and Black Pearl Geyser. Both are dormant with their last eruptions occurring in 1967.