Old Faithful is a world reknown geyser
that's located in Yellowstone National Park in
Wyoming. Vacationers come to visit the park
and watch this amazing site. Old Faithful
erupts more frequently than any of the other
big geysers, although it is not the largest or
most regular geyser in the park. Its average
interval between eruptions is about 91
minutes, varying from 65 - 92 minutes. An
eruption lasts 1 1/2 to 5 minutes, expels
3,700 - 8,400 gallons (14,000 - 32,000
liters) of boiling water, and reaches heights
of 106 - 184 feet (30 - 55m)!
    Old Faithful was named by the Washburn expedition of 1870. They were impressed by its size and frequency. It is not the biggest or most regular geyser in Yellowstone but it is the biggest regular geyser. Furthermore, it has been erupting in nearly the same fashion throughout the recorded history of Yellowstone. Through the years, it has become one of the most studied geysers in the park. One result of this close observation is that the Park Rangers are able to predict its eruptions fairly accurately. This makes Old Faithful geyser one of the easiest geysers in Yellowstone to see.