Excelsior Geyser Crater, formerly known as Excelsior Geyser, is a hot spring in the Midway Geyser Basin of Yellowstone National Park in the United States. Excelsior was named by the Hayden Geological Survey of 1871. Possibly the only known photograph of Excelsior in full eruption was taken by Frank Jay Haynes in 1888.
The Excelsior Geyser pool discharges 4,000 to 4,500 gallons (15,100–17,000 l) of 199 °F (93 °C). of water per minute directly into the Firehole River. In the late 1800's (there was possibly some activity in 1901 too) it was an active geyser that erupted frequently. Most eruptions were "only" 100 feet high, but some exceeded 300 feet (91 m) and were as wide as they were high. It is believed that powerful eruptions damaged its internal plumbing system, and it now boils as a productive hot spring most of the time.
In 1985, Excelsior returned to activity for a 46 hour period from September 14 to 16. These eruptions were relatively small at 30 feet (9.1 m) but a few were as much as 80 feet (24 m) tall and 100 feet wide, and threw water into the river. All of these eruptions lasted about 2 minutes at intervals of 5 to 66 minutes.
In the mid 2000s Excelsior did have violent boiling strong enough to be considered as eruptions, the boiling reached between 5 to 10 feet (1.5 to 3.0 m)and had a duration of seconds.