Upper Geyser Basin in Yellowstone National Park has the highest concentration of geysers anywhere in the world. This section of the UNESCO World Heritage-listed park is often overlooked because many people concentrate on Old Faithful, but it’s definitely worth walking through. There are a good number of geyser groups in the basin making for a good few miles of walking. This entry focuses on the Giant and Daisy Groups and describes only a few of the geysers and pools in the area.
The Giant Group starts very near to the Grand and Castle Group. The first feature is Beauty Pool, one of the most colorful pools in the entire Upper Geyser Basin. It’s 25 feet deep and 60 feet in diameter. The lower but still scalding hot temperature of the pool allows for different color bacteria to grow inside of it.
Chromatic Pool is next to and similar to Beauty Pool. The two pools are connected. When one pool has a low water level, the other is overflowing and has more brilliant colors.
Continuing along the path takes you to a bridge over the Firehole River and Oblong Geyser. It’s not much to look at and kind of tough to make out at first (it looks like a big pool), but this geyser erupts with a high volume of water, up to 10,000 gallons. It erupts every four to 13 hours and lasts five to seven minutes. Water shoots 20 to 40 feet up into the air. It is known to go dormant for a long time. Oblong Geyser was named by the 1871 Hayden Expedition for its oblong shape.
A long walk down the boardwalk takes you to the next group of geysers. Four geysers, most notably Giant Geyser, are visible from a small observation deck at a safe distance. Giant Geyser is true to its name. It erupts with great ferocity for about one full hour and can reach heights of 250 feet. These eruptions usually occur every six to 14 days but there are long periods of dormancy as well. Its broken cone is 12 feet high.
The other three geysers interconnected with Giant Geyser are Catfish, Mastiff, and Bijou. Catfish Geyser erupts for short periods of time up to 10 feet but can reach heights of 75 feet when Giant Geyser is erupting. Mastiff Geyser is Giant’s “watchdog”. When the water level rises in the vent and stays high, Giant will erupt eventually. Bijou Geyser is in an almost continuous state of eruption, often reaching heights of 15 feet. The excitement, however, starts when Bijou stops. This means Giant Geyser might erupt. From here, the boardwalk continues on to the Grotto Group.
To the west of the Giant Group is the Daisy Group. Comet Geyser, Daisy Geyser, and Splendid Geyser are all circled by a boardwalk. Splendid Geyser has infrequent but spectacular eruptions that can reach heights of 200 feet. Daisy Geyser erupts every 120 to 240 minutes and can reach heights of 75 to 150 feet.
Comet Geyser has the largest cone of the Daisy Group. It has been fairly steady since its discovery, splashing almost continuously up to six feet into the air. Many people mistake it for Daisy Geyser, but Daisy has a smaller cone.