Old Faithful

We visit the most famous geyser in the world and a few of its brethren.

Probably the most famous feature - natural or otherwise - in Yellowstone is Old Faithful. Old Faithful is a geothermal geyser Old Faithfulthat erupts periodically. Right now, the period is about 70 minutes. I say "about" because the period is not precise - you couldn't set your clock by it. Sometimes it is less than 50 minutes, sometimes it is more than 80 minutes; but, on the average, it fires off every 70 minutes, now. The Park Service has been tracking the eruptions and the period is getting longer. It used to be less than 40 minutes. Geysers are formed when water comes in contact with magma in areas of volcanic activity. There are no active volcanos in Yellowstone, but there are some inactive volcanos. Note the difference between an inactive volcano and an extinct volcano. Mt. St. Helens was an inactive volcano (its now active). Inactive volcanos are dormant, extinct volcanos are dead. I am from Reno, Nevada, and we have an inactive volcano - Mt. Rose. At the base of Mt. Rose there is a geothermal area called Steamboat. There are old pictures of this geothermal area that show geysers that were more spectacular than Old Faithful. However, Steamboat was not protected by a national park and was developed first as a spa and now as geothermal electrical power plant fields. Steamboat's geysers are gone, but the fissures in the ground are still there to see and you can hear the boiling water in them. So, to see a geyser, we had to go to Yellowstone.Old Faithful erruption #2

Old Faithful does not just turn on instantly. Its sits there and steams all the time. When it gets ready to erupt, it starts gurgling Old Faithful erruption #3and a small fountain appears. Over about 3 to 5 minutes, the fountain builds until it is over 100 feet high! Of course, the gurgling turns into a loud hissing noise and the tourists all start with the "Ooos" and "Ahs". For the first eruption when we were there, the experience was ruined by a construction crew running air compressors and power saws while rebuilding the boardwalk around the geothermal area. Oh, yes, there are boardwalk paths running through all the geothermal areas in Yellowstone. So you say, "Hey! You mean I can't walk on the ground in geothermal areas and get my tootsies warm?" Don't be disappointed! the boardwalks let you get up close to the geothermal features. If there were no boardwalks and you tried to walk across the geothermal fields, there are areas where there is only a thin crust on top of a boiling pool of water. Step on that and your tootsies would be really warm! Also, some of the geothermal areas are active, meaning that new boiling pools are constantly forming under crusts.

So what causes periodic geysers like Old Faithful? One theory is that the vent from the boiling subterranean water reservoir is plugged by a large boulder. As the water boils, the steam pressure builds up until it moves the boulder and the steam can escape to the surface, relieving the pressure, which lets the boulder drop back down and plug the hole, starting the cycle all over again. As the vent and the boulder become eroded by the steam over the years, leakage occurs and it takes longer to build up pressure. Also, the pressure does not build up as much; so the height of the eruption decreases. Yes, this means that, someday Old Faithful will cease to erupt. The Park Service does not know when the death of Old Faithful will occur. It could be tomorrow! So, you had better get your vacation plans in order and visit Yellowstone soon!

Peak of Old Faithful erruption

High resolution (148K) beginning of eruption

High resolution (119K) buildup of eruption

High resolution (104K) almost at peak eruption

High resolution (96K) peak eruption

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Last Updated 4 July 2004 by Art O'Connor