Geyser guide

Note: All these geysers are in Upper Geyser Basin, except Great Fountain Geyser, which is on Firehole Lake Drive. The information below is from "A Field Guide to Yellowstone's Geysers, Hot Springs and Fumaroles" by Carl Schrier.

Old Faithful

Interval: 30-120 minutes (the length of the eruption determines when the next one will be; a longer eruption indicates a longer interval)

Indicators: Splashing

Duration: 1.5-5 minutes

Height: 110-185 feet

Grand Geyser

Interval: 6-15 hours

Indicators: The basin slowly fills with water and covers the ledges surrounding the crater. Every 15-20 minutes neighboring Turban Geyser erupts, and if the level of the pool drops during Turban's eruption, it will take another cycle of Turban before Grand Geyser can erupt. A surging boil in the center of the pool indicates an eruption is imminent. Sometimes activity also depends on West Triplet and Rift Geysers, both of which are connected to Grand.

Duration: 9-16 minutes

Height: 140-200 feet

Riverside Geyser

Interval: 7 hours

Indicators: Water overflowing from the crater and surging for 1-2 hours before an eruption. Water begins to boil and splash 40-50 minutes before; a heavy surge or splash then triggers an eruption.

Duration: 20 minutes

Height: 75 feet

Daisy Geyser

Interval: 78-144 minutes (the interval can be affected by weather patterns)

Indicators: Splashing begins 20 minutes before an eruption from the larger of Daisy's two cones and 10 minutes before in the smaller cone; warm heavy splashing leads to an eruption, which reaches its maximum height in 45-60 seconds.

Duration: 2.5-4.5 minutes

Height: 75-150 feet

Castle Geyser

Interval: 9-11 hours

Indicators: None listed

Duration: 1 hour: 15 minutes for the water phase and 45 for the steam phase

Height: 60-90 feet

Great Fountain Geyser

Interval: 8-12 hours

Indicators: The crater fills and begins to overflow onto the terraces for 1 hour prior to an eruption (longer in the summer and fall); a few minutes before the eruption, water violently surges and boils.

Duration: 45-60 minutes

Height: 75-150 feet