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About Old Faithful, Yellowstone’s Famous Geyser

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.

Photo: iStock

Watch the Old Faithful Live Webcam at www.nps.gov/yell/learn/photosmultimedia/webcams.htm


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 beautiful visitor center  that tracks the time, height and length of an eruption to predict the next eruption.

How high does Old Faithful erupt and how long will it last?

Old Faithful Geyser next to the Old Faithful Inn
Old Faithful Geyser next to the Old Faithful Inn, illustrating how high the eruptions can reach. (Photo by Jeff Vanuga)

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.

Predicting Old Faithful Geyser Eruptions

The world’s most famous geyser, Old Faithful in Yellowstone, currently erupts around 20 times a day. These eruptions are predicted with a 90 percent confidence rate, within a 10 minute variation, based on the duration and height of the previous eruption. During visitor center hours, geyser statistics and predictions are maintained by the naturalist staff. This is done by good old-fashioned observation, timing with a stopwatch, and writing in a log book. Visitors can check for posted prediction times in most buildings in the Old Faithful area and on the webcam web page www.nps.gov/yell/learn/photosmultimedia/webcams.htm.

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.

I heard Old Faithful isn’t as faithful as it used to be. Is it slowing down?

People standing at Old Faithful in the 1800's
People standing at Old Faithful in the 1800sPublic Domain

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?

Aerial view of Old Faithful Geyser and Old Faithful Lodge.
Aerial view of Old Faithful Geyser and Old Faithful Lodge. (Photo: NPS/Jim Peaco)

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?

Bison Herd at Old Faithful
Wildlife enjoy the warmth of Yellowstone’s geysers but humans should be wary of the dangers of scalding water.iStock Photo

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?

A crowd watches Old Faithful erupt on a summer afternoon.
A crowd watches Old Faithful erupt on a summer afternoon.NPS Jacob W Frank

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. If you visit the park in the winter time, you’ll have Old Faithful nearly to yourself, if not completely.

More tips about avoiding the crowds.


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