The heart of Biscuit Basin is Sapphire Pool. Sapphire pool used to be surrounded by biscuit like rock formations, which is how Biscuit Basin got its name, however an earthquake in 1959 caused the pool to begin to erupt. It continued to erupt for several years cresting up to 150 feet in the air. These eruptions doubled the size of the pool and in the process destroyed the biscuits surrounding it. Eventually the eruptions subsided and it returned back to a pool.
Avaco Spring was named by the Hague Expedition back in the late 1800s. At that time it was just a simple spring but the earthquake of 1959 brought it to life. Today it is a fountain style geyser with 10 to 30 second eruptions every 1 to 20 minutes.
The Mustard Springs are actually a pair of springs that are tied to each other through subterranean tunnels. The two springs are similar in size and shape and both have mustard colored bacteria growing around their lining, which is how they get their name.
The Mustard Springs are separated by around 50 feet. Currently the East Mustard Spring, shown above, is in geyser status while the West Mustard Spring is a dry spring. This was not always true however, the West Mustard Spring used to be more active until a tremor in 1983 reversed this.
Shell Geyser is so named because of the rock formations in the lining that resemble the shell of a bivalve molluscs. Shell geyser is a small geyser that erupts at irregular intervals.
The largest geyser in the Biscuit Basin is the Jewel Geyser. It was originally named Soda Geyser by the Hayden Expedition, but was renamed in the early 1900s to Jewel Geyser because visitors believed that the rock formations in the lining resembled pearls.