Fan Geyser


Fan and Mortar Geysers are in close proximity to one another and almost always erupt in concert. The interval between eruptions ranges from 1-1/2 days to months. Most eruptions last about 45 minutes. Mortar Geyser erupts to heights of 40 - 80 feet while Fan can reach heights of 100 - 125 feet.

*Taken from the Old Faithful Area Interactive Map

Feature Type


Inventory ID



Latitude: 44.47435
Longitude: -110.8428
Survey Date: June 19, 1999

Geographic Area: Firehole River Drainage
Thermal Region: Upper Geyser Basin
Thermal Complex: Morning Glory Group
Ranger District Contact: Old Faithful District, Colleen Rawlings (307) 344-2701

Feature Data

Data Source Supplied By Sample Date Temp Vent Temp pH Cond Extended Data
Park 6/19/1999 48.2°C 92°C 8.2 1800 µS/cm No
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