Old Faithful Geyser Yellowstone Park | Wyoming USA

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estimate of next eruption time in upper left corner

Predicting Old Faithful:

The time to the next eruption, the interval, is predicted using the duration of the current eruption. The duration is timed from the first heavy surge which lifts water skyward at the start of the eruption until the last small splash above the cone at the very end. The longer the eruption lasts, the longer the interval until the next eruption. For instance, a 2 minute eruption results in an interval of about 55 minutes whereas a 4.5 minute eruption results in an interval of about 90 minutes. See the following table for more information.

It is not possible to predict more than one eruption in advance.

Duration 1.5 min 2.0 min 2.5 min 3.0 min 3.5 min 4.0 min 4.5 min 5.0 min
Interval 50 min 57 min 65 min 71 min 76 min 82 min 89 min 95 min

One of the best ways to anticpate when Old Faithful will blow next is to follow the massing of people observing the geyser. Timing at the park will help observers know when to turn their attention to the geyser. Follow the crowd!