When coming to see Old Faithful Geyser Yellowstone National Park, many first-time visitors have some questions about this most popular geyser. Here are the answers to a few most-asked questions.

Planning to See the Eruption

Q. When will Old Faithful erupt?
A. Intervals between eruptions vary between 45 to 110 minutes. The predicted times of eruptions are posted in most of the buildings around the Upper Geyser Basin.

Q. Is Old Faithful Geyser Yellowstone Park slowing down and becoming less “faithful”?
A. Old Faithful went from 21 eruptions a day to 20 a day after the 1959 earthquake, which is not much of a slowdown, depending on how you look at it. Scientists feel it’s a considerable slowdown, but visitors rarely see a difference. Eruptions can be predicted within about a ten-minute variation.

The Extent and Temperature of the Eruption

Q. How high does the geyser erupt?
A. Old Faithful Geyser Yellowstone varies in the height of eruptions anywhere from 100 to 180 feet, averaging about 130 or 140 feet.

Q. How long does the eruption last?
A. The eruptions usually last between one and a half minutes to five minutes.

Q. How many gallons of water shoot out during one eruption?
A. The estimates are about 3,700 gallons for a short eruption of about one and a half minutes, and 8,400 gallons for one of four and a half minutes.

Q. How hot is the water that comes from Yellowstone’s Old Faithful Geyser?
A. The water during an eruption has been measured at 204 degrees F and the steam at over 350 degrees F.