Old Faithful geyser was given its name by explorers during the 19th century. It lies in the state of Montana, within the boundaries of Yellowstone National Park. It was first photographed in 1872, the year Yellowstone became the first national park, and was honored with a postage stamp one hundred years later. Thousands come each year to watch Old Faithful and other geysers erupt, hear rangers lecture, and visit the Old Faithful Visitor Center and Museum.
The reason Old Faithful erupts fairly regularly has to do with how a geyser is formed and how it works. A system of holes and natural “pipes” leading from one hole to another underground are filled with water on a regular basis when cool ground water seeps into them. Deep in the ground, superheated water comes up into the lowest holes. When water is superheated it is hotter than steam, but stays liquid because of great pressure. When the cool water meets the superheated water, the higher, cool water puts more pressure upon the superheated water. The superheated water soon heats the cool water, and the cooler water molecules move faster. Minerals around the natural “pipes” and the ground surrounding Old Faithful hold down the hot water. This pressure finally bursts through the Old Faithful vent and the hot water, released from being contained, bursts into steam, creating a show for tourists and visitors to “Ooh and Ah”.Old Faithful is not the tallest of geysers in the park, nor is it the most regular, but with eruptions of 106 to 180 feet, and a fairly predictable schedule, it is one of the most impressive and famous natural shows the park has to offer. The sight of 3700 to 8400 gallons of hot water bursting into the air in a few minutes is an impressive sight. Contrary to myth, Old Faithful does not erupt every hour on the hour, but at varying intervals depending upon how much steam was spewed at the previous eruption. The park rangers observe how long each eruption lasts to calculate when the next eruption should take place. Old Faithful’s eruptions usually last between one and a half to five minutes. The time between each eruption ranges from 44 to 125 minutes.
Old Faithful is known as a cone geyser because its vent is conical, making its eruptions spew upward in a vertical column. As you might guess, the water coming out of the cone is extremely high. The temperature at the vent is around 204 degrees Fahrenheit, so benches are provided approximately 300 feet away for safe viewing.
One Old Faithful secret has created erroneous rumors that the geyser does not shoot as high as it did in the last century. The secret is that the benches have been moved further away from the geyser creating an illusion. It is difficult to judge the height of the eruptions due to the fact that there is nothing next to it with which to compare the height of the eruptions. The illusion is similar to that found in a movie theatre watching a show. The closer you sit to the screen, the higher the top of the screen appears. Fortunately, Old Faithful shows no signs of lessening its magnificent show any time soon.