GOSA (The Geyser Observation and Study Association)

Upper Geyser Basin

Predicted Geysers


Five of the major geysers in the Upper Geyser Basin are predicted by the Park Rangers at the Old Faithful Visitor Center. Prediction times for these geysers are posted by the rangers at the visitor center and, in the summer, at the geysers. Predictions are also listed at the Old Faithful Inn and Lodge.

All of the predicted geysers are worth seeing. Each is different. The two most predictable geysers are usually Old Faithful and Daisy. The most spectacular, and the must-see geyser is Grand.

Please Note: All descriptions below are based on activity in 2001 and early 2002. Activity may, and most likely will, change in the future.

[ Map ]

[ Castle ] [ Daisy ] [ Grand ] [ Old Faithful ] [ Riverside ]

Grand Geyser

(Left to Right) Vent Geyser, Turban Geyser and the start of a second burst from Grand Geyser.

Grand is a fountain-type geyser. Its interval is usually around 8-12 hours, its height about 150-180 feet and its duration is about 10-12 minutes. It will often stop after about 9 minutes and then restart after a minute or so. This second "burst" and any subsequent bursts are often among the tallest if not the tallest of the eruption. Be sure to wait and see if there is a second burst.

Grand Geyser is closely connected to many of the geysers in its immediate vicinity. It is most easy to see this connection in Vent Geyser and Turban Geyser.

What to look for:

First, it is easy to get confused when looking for Grand Geyser. Of course, the Park Service has put out a sign to help you but the first thing most people notice is the large raised rim around Turban Geyser and they miss the large flat pool just to the right of Turban. This large pool, with almost no rim, is Grand Geyser.

When Grand Geyser finally erupts, it does so just before the start or within one, or rarely two, minutes after the start of a Turban eruption. If Grand doesn't start at this time, you'll have to wait for the next eruption of Turban and hope.

After an eruption of Grand, Grand's pool is empty. Water slowly fills the pool and reaches first overflow about 5 hours after the eruption. Once in overflow, it can be noted that the pool rises and falls in approximately 20 minute cycles. These cycles correspond to the eruptions of Turban Geyser. At about the time Turban starts, the water in Grand will usually begin to slowly drop and will continue to drop as Turban erupts. Once Turban stops, the water in Grand will slowly begin to rise again. With some practice, a good eye and favorable weather conditions, you may be able to see these drops and rises. Look around the front edge of the pool and you will notice some slightly raised sinter formations. At high water they form small islands or may even be covered by the water, at low water they will stick out of the water by about an inch. What you are looking for is for the water to stay high at the time you expect Turban Geyser to erupt. If this happens, you then want to look for large ripples (called waves) on Grand's pool. These waves are hard to see. It often takes practice to see them. Once the waves start, you are almost assured of an eruption. The eruption will start just