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Nature Notes: Old Faithful is indeed faithful

Winter view of an Old Faithful eruption, captured from the NPS Webcam

Millions of people have watched an eruption of Yellowstone National Park’s Old Faithful geyser. I confess my favorite method of watching an eruption is while sitting in my recliner. Winter eruptions are especially enjoyable when I catch one during a Yellowstone snowfall, a scene of white on white on gray.

Do not get me wrong, I have stood on that boardwalk on a warm summer day, along with 1,000 of my closest friends, but I prefer my recliner. After all, we cannot all be so lucky as the two people in the above photo, enjoying an eruption all by themselves. The National Park Service maintains a streaming webcam at for us recliner tourists.

The name Old Faithful has proven to be a good choice. Members of the Washburn Expedition, the first official expedition to enter the park in 1870, named this geyser. Another early name was Eternity’s Timepiece, so thank goodness the Old Faithful name stuck.

No one knows how long Old Faithful has been erupting but people have been timing its eruptions over the past 160 years. During those years, Yellowstone visitation has risen into the millions and infrastructure to accommodate those visitors has built up along three sides of the geyser’s cone, with extensive parking lots beyond them. Yet during all those years, Old Faithful has remained amazingly consistent.

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Eruptions occur day and night, summer and winter, with each eruption following the last by 51 to 120 minutes, with an average of 89 minutes. The average interval has increased slightly over the years, caused by large earthquakes such as the 1959 Hebgen Lake Earthquake. However, every eruption has gone off no more than 120 minutes after the last one.

Each eruption lasts 1.5 to 5 minutes with a height between 106 and 180 feet and an average height of 130 feet. These have also remained constant over the last 160 years.

Old Faithful is the most studied geyser in Yellowstone and rangers can predict its eruptions to within 10 minutes. Over the years, scientists have discovered that the length of the last eruption predicts the wait time to the next eruption. A two-minute long eruption predicts an interval of about 55 minutes while a 4.5-minute eruption predicts a 90-minute interval. Apparently, a longer eruption requires more time to build up to the next eruption.

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