Upper Geyser Basin
Predicted Geysers
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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 1997. Activity may, and most likely will, change in the future.
[ Map ]
[ Castle ] [ Daisy ] [ Grand ] [ Old Faithful ] [ Riverside ]
(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.
- Vent Geyser usually only erupts immediately after the start of a Grand eruption and intermittently for an hour or so afterwards. On rare occasions it can start just before Grand and on extremely rare occasions it has erupted by itself.
- During the hours prior to an eruption of Grand, Turban Geyser erupts every 15-25 minutes for about five minutes. During Grand's eruption, it will erupt continuously often increasing in size from its normal 5-10 feet to about 20 feet. For the hour or so after Grand's eruption Turban erupts intermittently with Vent 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 prior to Turban or within a minute or so of Turban. If it doesn't erupt within this period, sit back and wait for the the next Turban eruption.
Once Grand erupts, there is the possibility of more than one burst. A Grand burst is defined as continuos eruption of water from Grand. The shorter this first burst, preferably less then 10 minutes, the more likely it is that you will see a second, third or more bursts. (The most bursts seen in one eruption during the last few years is 11 bursts but the average is usually between 2 and 4 bursts.) After a burst has ended, watch Grand's pool. Sometimes the water will be out of sight, sometimes it will still be visible. Watch to see if the water rises. If the water rises and begins to bubble be prepared for a spectacular sight as Grand erupts to its full height in one continuous motion. If the water drops, well, there's always the next eruption.
Daisy is a cone-type geyser. Its interval is usually 110-130 minutes, its height 60-75 feet and its duration 3-4 minutes. Most of the time it is very predictable. The exception to this rule is when nearby Splendid Geyser is active. When Splendid is active there is a complex interplay between Splendid and Daisy. Sometimes Daisy will erupt alone, sometimes Splendid will erupt alone and sometimes both will erupt together. These concerted eruptions are spectacular. During some concerted eruptions, Splendid and Daisy seem to feed off of each other. In these eruptions, Splendid can reach over 150 feet (218 feet was measured once) and Daisy can reach over 100 feet. It is truly amazing to see such large eruptions within 200 feet of each other. Unfortunately, concerted eruptions are rare. 1985-1987 saw a number of concerted eruptions but then Splendid went nearly dormant until 1996. For the first time in a decade, 1997 saw concerted eruptions. Unfortunately, this activity appeared to be stopping at the end of 1997.
What to look for:
When Daisy Geyser is regular (in other words, when Splendid is not active) you can usually predict the eruptions very accurately using the current average interval and the time of the last eruption. In fact, this is so accurate that the Rangers often predict two eruption of Daisy in advance just using the interval.
But, what happens if you don't know when Daisy last erupted or what its current interval is? Well, there are a couple of things you can look for.
First, don't confuse the locations of Daisy and Comet Geysers. Comet is a nearly constantly active small geyser with a large half cone located in the center of the Daisy Group. Daisy is located closer towards the hill you walked up to get to the Daisy Group. It too is surrounded about halfway by a sinter rim but this rim is shorter than Comet's. On Daisy's rim are located two small cones. Each of these is a small geyser. The smaller of the two cones starts erupting about 20-30 minutes before Daisy. The larger of the two cones starts erupting about 10-15 minutes before Daisy.
Riverside is a cone-type geyser. Its interval is usually 5 1/2 to 7 hours, its height about 75 feet and its duration about 1/2 hour. The water phase of the eruption lasts about 20 minutes and is followed by a steam phase. Situated on the bank of the Firehole river at the base of a wooded hill, Riverside has one of the most picturesque settings of any geyser. Riverside's eruptions are highly bi-modal. Eruptions usually occur either about 1/2 hour before or 1/2 hour after the current average. No one know how to determine which of these two, the short interval or the long interval, will occur. If this could be determined, Riverside would be one of the most predictable geysers in the park.
What to look for:
You watch Riverside from a viewing area across the Firehole river from the geyser. From this position, Riverside's formation looks something like a chair. There is a vent high up on the back and another vent in the seat of the chair. Except for some minor splashing, the geyser erupts from the lower vent in the seat of the chair. About 1 1/2 to 2 hours before the eruption the main vent in the seat of the chair begins to overflow into the river. This overflow is variable. About an hour later, the small vents behind the main vent will begin to bubble and boil. The activity fluctuates but seems to build as time progresses. Finally a splash or two will be seen in the upper vent at the top of the chair back. One of these splashes from the upper vent will be large enough to spill water into the river, this usually starts the eruption.
Castle is a cone-type geyser. Its interval is 9-11 hours and its height is 60-90 feet. The twenty minute water phase of a major eruption is followed by a 40 minute steam phase. The first 15 minutes of the steam phase is relatively forceful and fairly loud so try to be close for this part. As in most geysers that have a steam phase, the change from water to steam is gradual and an exact time for the change can rarely be noted.
Castle often has minor eruptions which last only a few minutes. Any eruption that stops prior to the steam phase is considered a minor eruption. When Castle has a minor eruption, it becomes unpredictable until it has its next major eruption.
Castle is probably a very old spring. Estimates put the age of its 12 feet high cone at 5,000 to 15,000 years. It would take that long for the sinter to build up so high. Even more remarkable is that Castle's cone sits on top of an even more massive sinter formation deposited by an earlier spring.
What to look for:
Many eruptions of Castle start with almost no warning. During the period between eruptions, Castle will often splash but this usually does not appear to indicate anything. The easiest way to determine if Castle is due to erupt is by using the current average interval and the time of the previous eruption.
The one time that splashing does indicate something is when it is what is called "sloppy play". This occurs after a minor eruption. Sloppy play is characterized by frequent splashes and jetting and usually starts soon after the minor eruption and continues until the next major eruption.
Major and minor eruptions start the same but a minor stops without warning after a few minutes of play. In recent years, major eruptions have been the norm but Castle seems to like to throw in that occasional minor eruption just to keep everyone on their toes.
Old Faithful is a cone-type geyser. Its intervals range from 35 to 120 minutes, its duration is 1 1/2 to 5 minutes and its height is 90 to 184 feet. The rangers say that 90% of their predictions are within +/- 10 minutes.
Old Faithful was named by the Washburn expedition of 1870. They were impressed by its size and frequency. It is not the biggest or most regular geyser in Yellowstone but it is the biggest regular geyser. Furthermore, it has been erupting in nearly the same fashion throughout the recorded history of Yellowstone. Through the years, it has become one of the most studied geysers in the park. One result of this close observation is that the Park Rangers are able to predict its eruptions fairly accurately. This makes Old Faithful geyser one of the easiest geysers in Yellowstone to see.
Old Faithful is deceiving. The benches around the geyser are over 300 feet from the geyser but with nothing to judge the distance by, I rarely realize just how big the geyser is until I get further away. Personally, I like the view from Geyser Hill. As with any geyser, watch the wind direction or you may only see steam.
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 | 48 min | 55 min | 70 min | 72 min | 74 min | 82 min | 93 min | 100 min |
Common Misconceptions:
- Old Faithful plays on the hour every hour
- This legend dates back to the early history of Yellowstone Park. Old Faithful has never played every hour on the hour. It is just as likely to play on the hour as it to play 17 minutes after the hour or 23 minutes after the hour or ......
- Old Faithful plays hourly
- Old Faithful's intervals range from 35 minutes to 2 hours. You might see one interval of 60 minutes but it is very unlikely that you will see two in a row. This misconception seem to date back to the 1870 Washburn expedition where one of the members reported that Old Faithful played "nearly hourly". Each day there are usually between 21 and 23 eruptions so "nearly hourly" is about true if you look at the average but on an eruption to eruption basis, hourly eruptions have never been the norm. No geyser, including Old Faithful, plays at set times and intervals. There is always some variation.
- Old Faithful is slowing down
- People expecting an hourly eruption are often surprised when they have to wait through a 90 minute to 2 hour interval. They then think that Old Faithful is slowing down. Old Faithful still has its same interval range, 35-120 minutes, that it has always had. In the last few years, long interval eruptions have been a little more common than they were a few decades so the yearly average has increased by a few minutes over what it was a few decades ago but this change is very small and the range of intervals is still the same.
- Old Faithful is getting shorter
- Measurements show that Old Faithful is still as tall as it has ever been, 90-180 feet. There are a number of reasons people may feel that Old Faithful is getting shorter. They may have seen an exceptionally tall eruption last time and this time saw a more ordinary or even a short eruption. The first time they saw an eruption they may have been more excited and their excitement caused them to over estimate its height. Or they may have first seen it a number of years ago when it was possible to get closer to the geyser. To accommodate the summer crowds, the boardwalk has since been moved further back from Old Faithful. Many people don't realize just how far from the geyser the boardwalk is. With nothing to judge the distance by, most people severely underestimate the height of Old Faithful. Its not until they get back farther from the geyser and see the buildings around the geyser that they realize just how big the geyser is.
- Old Faithful erupted late or early
- It is only possible to make predictions of the time Old Faithful may erupt. The geyser will erupt when it is ready. Its the prediction that is early or late not the geyser.
What to look for:
A joke among some geyser gazers, when asked in the summer by a park visitor about when Old Faithful will next erupt, is to ask the visitor about the "Old Faithful Indicator." Of course, there is no Old Faithful indicator in the true sense of the idea. What the geyser gazer is actually referring to is the crowd seated around Old Faithful. After the eruption everyone leaves. As the predicted time for the next eruption approaches, the benches begin to fill and eventually overflow. Thus, by looking at the crowd, you can get a rough idea as to when the next eruption is predicted.
If the indicator is broken, say you are lucky enough to be in the park when there are no crowds, then you'll have to look at the geyser. Old Faithful goes through a period of preplay prior to an eruption. This preplay can last anywhere up to twenty minutes. The preplay consist of splashing and small jetting which often occurs every few minutes reaching from 1 to (rarely)20 feet in height. It often lasts just long enough for some excited visitors to start taking pictures. The eruption usually starts from what initially looks like just another preplay jet. Short interval eruptions occasionally start with the first splash seen above the cone but most require a period of preplay.
Once the eruption starts, the jetting will grow, stop, grow again and in two or three of these steps, reach maximum height. It takes 10-20 seconds to reach full height. Unfortunately, the full height is maintained only for a short time. Within a minute, the eruption starts waning. This is the when you need to pay close attention if you want to predict the next eruption. The interval to the next eruption is based on the total duration of the current eruption. This includes the unimpressive play that ends the eruption. The main visible difference between a long and short eruption is the duration of the end play. In a short duration eruption the end play stops quickly. In a long duration eruption you may see up to 4 minutes of unimpressive, 5 feet tall, end play. It just doesn't seem fair that a long wait is due to such wimpy play.
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