Discovered in 1870 by the Washburn Expedition, Old Faithful geyser was named for its frequent and somewhat predictable eruptions, which number more than a million since Yellowstone became the world’s first national park in 1872.
Old Faithful is located in Yellowstone's Upper Geyser Basin in the southwest section of the park. The geyser-viewing area is the most accessible and visitor-friendly in the park with bench seating, a large parking lot, and a ranger station that tracks the time, height and length of an eruption to predict the next eruption.
When does Old Faithful erupt?
Basic prediction of Old Faithful is dependent upon the duration of the previous eruption. During visitor center hours, geyser statistics and predictions are maintained by the naturalist staff. People speak of the average time between eruptions. This is misleading. The mathematical average between eruptions of Old Faithful is currently 74 minutes, but it doesn't like to act average! Intervals can range from 60-110 minutes. Visitors can check for posted prediction times in most buildings in the Old Faithful area.
How high does Old Faithful erupt and how long will it last?
Old Faithful can vary in height from 100-180 feet with an average near 130-140 feet. This has been the historical range of its recorded height. Eruptions normally last between 1.5 to 5 minutes.
I heard Old Faithful isn't as faithful as it used to be. Is it slowing down?
It depends on what you call faithful. The famous geyser currently erupts around 20 times a day and can be predicted with a 90 percent confidence rate within a 10 minute variation. Prior to the 1959 earthquake, Old Faithful erupted 21 times per day. That's a significant decrease in activity for geologists tracking each eruption, but to visitors seeing one or two eruptions... it looks just fine.
Related: Read about the mistreatment of Old Faithful in the early years of the park.
How many gallons of water are expelled during an eruption?
It depends on the duration of the eruption. Scientists estimate that the amount ranges from 3,700 gallons (for a short duration of 1.5 minutes) to 8,400 gallons (for a longer duration of 4.5 minutes).
How hot is the water in Old Faithful?
It's hot. During an eruption, the water temperature at the vent has been measured at 204°F (95.6°C). The steam temperature has been measured above 350°F! Stay a safe distance from thermal features and never leave the boardwalk to walk on a geyser's fragile crust.
Read more about the dangers of geysers.
How can I avoid the crowds at Old Faithful?
Since Yellowstone brings in upwards of 4 million visitors a year, securing a great view of the geyser’s cone can be especially challenging, even though the scalding mist can reach 90 to 120 feet into the air for all to see.
To have a more intimate experience, avoid times from noon until 6 p.m. when bus tours and visitors are expected to arrive. Also consider visiting Yellowstone during the shoulder seasons, or at winter when you could very well get a private eruption viewing all your own.