The Lower Geyser Basin is the largest geyser basin in area, in Yellowstone. It covers approximately 11 square miles. By comparison, the Upper Geyser Basin only covers about one square mile. Because of its large size, the thermal features in the Lower Geyser Basin tend to be clumped in widely spaced groups. The easiest grouping to get to and probably the most interesting to explore is the Fountain Paint Pot area.
Also located in the Lower Geyser Basin is Great Fountain Geyser. Great Fountain is the only predicted geyser in the Lower Geyser Basin and the only predicted geyser in Yellowstone that you can drive to. Predictions for this geyser are posted at the Old Faithful Visitor Center and, when staffing allows, at the geyser.
| Fountain Paint Pot Trail: Along this short walk you will see very good examples of most types of thermal features found in Yellowstone. These features include some very pretty hot pools, steaming fumaroles, erupting geysers and probably the best easily accessed mudpots in the park. The area is highly active and at least one geyser is usually erupting here at all times.It takes about 1/2 hour to get around this area. The parking lot is small and it can be hard to find a parking space but the sights along the trail are well worth the hassle.
Great Fountain Geyser
Great Fountain Geyser sits in the middle of one of the prettiest sinter formations in the park. The sinter forms a series of terraced concentric reflecting pools around the geyser. Even if the geyser isn’t erupting, it is worth driving past to see the pools.
Great Fountain is a fountain-type geyser, erupting in a series of bursts through a pool of water. Its interval between eruptions ranges from 9 to 15 hours but its short term average interval is usually stable enough that the eruptions can be predicted to within an hour or two. Great Fountain’s maximum height ranges from about 75 feet to over 220 feet. Its duration is usually about one hour but durations of over two hours have been seen.
Great Fountain is a major geyser, but many people, when hearing it erupts to over 200 feet, are disappointed by its more common maximum of less than 100 feet. For this reason, Great Fountain has earned a number of pejoratives, such as The Flounder. The smaller eruptions of Great Fountain are still large and pretty but pale in comparison to the truly huge eruptions.
Great Fountain erupts in a series of distinctly spaced bursts. The first group of bursts lasts about ten minutes.
Then there is about a five minute quiet period followed by another five or so minutes of activity. These quiet and active episodes continue until the end of the eruption. Usually the first period of activity is the tallest and strongest, with the first and sometimes the second burst being the strongest of the eruption. Sometimes, the largest burst will occur during the third active period. This especially seems to occur when the first period has been uninspiring. Rarely, large bursts will continue long into the eruption.
Great Fountain is the only major geyser you can truly watch from your windshield. This is especially nice in bad weather.