Old Faithful erupts every 35-120 minutes for 1.5-5 minutes to a height of 90-184 feet. The rangers say that 90% of their predictions are within +/- 10 minutes. The time to the next eruption is predicted using the duration of the current eruption. 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 50 minutes whereas a 4.5 minute eruption results in an interval of about 85 minutes. It is not possible to predict more than one eruption in advance.
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