Biscuit Basin is a geothermal area located inside Yellowstone National Park in Wyoming. It was named after biscuit-like sinter deposits that once surrounded the bright blue Sapphire Pool in the basin. Even though the biscuit deposits barely exist today, various other colorful pools and interesting formations are worth a visit.
Part of Upper Geyser Basin, this thermal group is located about 4 miles northwest on Grand Loop Road from Old Faithful Geyser. It is accessible via a footbridge across Firehole River, and a short 1/4 miles boardwalk provides a safe walking trail to observes the features of this basin.
There are many large and small, prominent and unnamed geysers across the basin. These are some of the features that can be easily spotted from the boardwalk.
Black Opal Spring:
Black Opal Spring is a large blue pool and features bright orange communities of bacteria on one end. Last powerful eruptions occurred in 1953 and it has remained quiet since.
Black Diamond Pool:
Black Diamond is one of the three closely located pools, the others being Black Opal and Wall Pool. Though its neighbors have remained inactive since the 1950s, Black Diamond has had powerful eruptions throwing rocks and debris as high as 50 feet. Its last recorded eruptions were in 2016.
Wall Pool is the third neighbor and its activity is similar to that of Black Opal. No known eruptions have occurred since the 1950s.
Black Pearl Geyser:
Black Pearl is a small dark hole with colorful bacteria growing on its walls and bright green algae around its rim. It has been dormant since the 1960s and its activity now is reduced to only steaming.
Biscuit Basin was named after biscuit like deposits around Sapphire Pool. A 1959 earthquake caused Sapphire Pool to erupt violently and as a result biscuit deposits around its rims were destroyed and the crater doubled in size. Sapphire Pool retains its crystal clear blue color and boils violently with occasional bursts.
Sapphire Pool Run-off:
Sapphire Pool has a colorful run-off that flows a long way to the other side of the boardwalk. The green and bright orange colors are a result of algae and bacteria that thrive in warm temperatures and wet conditions. These bacteria are called "Thermophiles", and their colors are determined by the temperature, different colored bacteria grow in varied temperatures. These colorful run-offs can be seen in all the basins across the park.
Thermophiles are microorganisms that thrive in heat. They live in hot waters of geysers and their run-offs, adapting to iron-rich and acidic conditions. The number of Thermophiles living in a ten-inch square can exceed total human population on earth.
The 1959 earthquake made Avoca Spring an active geyser. It is part of the Silver Globe geyser complex. With no set duration or intervals, it continuously churns water within its crater and has strong eruptions.
Silver Globe is a group of 6 geysers of different sizes. The one seen in the photo below is close neighbor to Avoca Spring. It is the weakest and most dormant geyser of the complex.
It is a small green steaming pool filled with crystal clear water and bright yellow bacterial rim. It is a dormant geyser and eruptions are extremely rare.
Jewel Geyser, which was originally named Soda Geyser, was then renamed for the beaded sinter formations around its vent. It is a frequent and regular spouter with a series of medium to large bursts. It erupts at regular intervals of about 8 minutes.
Mustard Spring East:
Mustard Springs East and West are a group of geysers 50 feet away from each other. They received their names for the mustard colored deposits around their vents. East Mustard Spring is more active among the two.
Sinter deposits around its crater resembling a clam shell gives this geyser its names. Shell Spring has very irregular eruptions. Water fills up in its crater, boils and churns vigorously before erupting and as it subsides the water drains back.
Similar to Black Pearl, Coral Geyser has been dormant since the 1960s and its activity now is reduced to only steaming.