Old Faithful geyser is probably the most recognized geyser out of the thousand located throughout the world. It is the centerpiece of Yellowstone National Park in Wyoming and thousands of visitors from around the world visit it every year. It was officially discovered and named in 1870 by the Washburn Expedition, the most famous expedition that explored the Yellowstone region. Old Faithful was named because of its extremely regular and predictable eruptions. The geyser is so reliable that park rangers are able to estimate daily eruptions times with an error of only ten minutes. For comparison, only a few other geysers have predictable eruptions times, but the error is hours or even days. Most geysers have completely unpredictable eruptions.

Old Faithful is located in the Upper Geyser Basin along with numerous other geysers and hot springs. It is classified as a “cone geyser” because its opening has a cone several feet high around it. The cone was created by minerals present in the geyser water. The main reason that the geyser is thought to be so reliable is because its underground reservoir system is kept separate from other geyser systems in the basin. Old Faithful erupts about every 90 minutes and the eruptions last for several minutes. Water and steam over 204 ° F are pushed up over one hundred feet high. It is commonly thought that Old Faithful is the tallest geyser in the world, however that honor goes to Steamboat geyser. Steamboat is located in another geyser basin in Yellowstone and its infrequent eruptions reach 300 to 400 feet high.

Over 137,000 eruptions of Old Faithful have been documented, making it the most studied geyser in the world. In 1938, the geologist Harry M. Woodward was able to find a correlation between the duration of eruptions of Old Faithful and the interval between eruptions. This was the first correlation found for geysers. He found that shorter eruptions that lasted less than two minutes were followed by a shorter interval until the next eruption that averaged about 65 minutes. Longer eruptions were followed by longer intervals averaging about 94 minutes. Shorter eruptions do not deplete all the water out of the geyser’s reservoir system, allowing it to recharge faster before the next eruption, while longer eruptions drain all the water and require more time to recharge.

Various documented earthquakes over the years were found to have an effect on the eruption pattern of Old Faithful. Earthquakes in 1959, 1983, and 1998 successively lengthened the time between eruptions. Early accounts noted that these intervals averaged 76 minutes, while today the time averages 90 minutes. Researchers think that these intervals were lengthened because the earthquakes adversely affected the water levels around the geyser. Interestingly, the earthquakes did not have a negative effect on the predictability of Old Faithful eruptions. Eruption times are actually more predictable now than before the earthquakes.

Old Faithful is prominently located at the front of the geyser basin and is easily accessible. A cement walkway runs around the geyser and numerous benches are available for people waiting to see the eruption. If you are planning on visiting Old Faithful during the summer, I recommend seeing it early in the morning or later in the day after dinner. This way you can avoid most of the crowds that are bussed in during the day. To really avoid crowds, try visiting the geyser during the winter.

For those who would like to see Old Faithful without making a trip, a live webcam of the geyser is currently available at: http://www.nps.gov/yell/oldfaithfulcam.htm

kalen notes:"You didn't mention the desecration of the cone by over-zealous tourists." It would appear that Old Faithful, like many other features in Yellowstone, has been the victim of ignorant tourists who have tried to throw various objects into the geyser's opening. These objects partially block the flow of water and can be "cemented" permanently in place by minerals in the geyser water. So many objects have been thrown into the opening that Yellowstone park rangers have built some sort of suction device to try and remove them. It is thought that stuck objects will eventually alter the eruptions of Old Faithful forever. How sad.


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