Old Faithful

Old Faithful is a cone geyser in Yellowstone National Park in Wyoming, United States. It was named in 1870 during the Washburn–Langford–Doane Expedition and was the first geyser in the park to be named. It is a highly predictable geothermal feature, erupting on average every 92 minutes, with the period between eruptions ranging from as short as 35 minutes to as long as 120 minutes. The geyser and the nearby Old Faithful Inn are part of the Old Faithful Historic District. Eruptions can shoot 3,700 to 8,400 US gallons of boiling water to a height of 106 to 185 feet lasting from 1½ to 5 minutes. The average height of an eruption is 145 feet. Intervals between eruptions have ranged from 34 to 125 minutes, averaging 66½ minutes in 1939, slowly increasing to an average of 90 minutes apart since 2000, which may be the result of earthquakes affecting subterranean water levels.