|About the Site|
|Yellowstone National Park (3)|
The most famous of Yellowstone's hydrothermal features is unquestionably Old Faithful whose eruptions have been witnessed by millions. It is almost certainly the most well known geysers, or perhaps hydrothermal feature of any kind, in the world.
Old Faithful's fame is probably due to the fact that it erupts more frequently, and more regularly, than any other big geyser. It is one of about 6 geysers in the park which erupt on a predictable daily basis to a height of 100 feet or more.
Old Faithful has probably been a geyser for hundreds of years, perhaps for 200-300 years and likely less than 700. It was named for its perceived regularity by members of the Washburn-Longford Expedition--possibly General Washburn himself--in 1870.
Although there is a popular misconception that the geyser erupts once per hour, Old Faithful is not quite that regular. In reality, the geyser erupts on the average about every 70 or 80 minutes, with a range of about 33 to 120 minutes.
The intervals suggested above means Old Faithful erupts from 18-23 times per day.
As it happens, the average interval between eruptions at Old Faithful has been increasing. The Hebgen Lake earthquake in 1959 is believed to have increased the period between eruptions, as did the Borah Peak earthquake in Idaho in 1983.
Old Faithful erupts to a height of about 106 to 184 feet. A short eruption may last 1 1/2 to 2 minutes, while a long one may last 3 to 5 minutes. Each eruption expels some 3500-8000 gallons, or 11-12,000 gallons, of water, depending on the source.
Old Faithful is nourished by the meltwater from 250 feet of snow annually. A geyser like Old Faithful must have a tube which feeds its opening and is nearly vertical.
The "cone" at the base of Old Faithful is actually composed of tree stumps which have been covered by geyserite. With Old Faithful and other geysers, superheated water passes rhyolite, volcanic ash, and tuff. The water becomes laden with silica. It is the silica which forms the geyserite from which cones and the basins around the base of geysers and hot springs are composed.
Old Faithful is located in the Upper Geyser Basin, one of the most spectacular sites for geothermal features in the world. One fifth of all geysers in the entire world are located within a mile of Old Faithful.
Old Faithful is easy to see as it is located adjacent to a number of visitor resources and services. It is very near Old Faithful Inn, and other lodges, and the visitor village there also includes a Post Office, restaurants, auto repair, and other amenities. A boardwalk (below) surrounds the site, and the seating there is often packed for eruptions.
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