Why she blows: Secrets of Old Faithful revealed
JACKSON HOLE, WYO – An immense underground chamber has finally been identified as the ‘holding tank’ for the water that causes Old Faithful to erupt on such a regular schedule. The discovery of the cavern is new and coincides with similar evidence found earlier this year by Russian scientists in Kamchatka’s Valley of the Geysers, explaining how geysers work while dispelling previous long-held theories that a long, narrow tube was necessary for eruptions to take place.
University of Savoie (France) geophysicist Jean Vandemeulebrouck published the results of his study in the March 30 issue of Geophysical Research Letters – a scientific trade journal. He says the large void is approximately 50 feet tall by 60 feet wide. The cavern connects to a natural conduit pipe at a 24-degree angle that feeds Old Faithful’s maw.
Vandemeulebrouck and his team used seismic array data obtained from a 1992 research project to better learn how Old Faithful blows her top every 92 minutes or so. The answer lies in tremor-creating popping gas bubbles that allow scientists to map the water storage area and water flow of the world’s most famous geyser. Vandemeulebrouck says the previously-unknown cavern lies 50 feet under the earth’s surface, to the southwest of the Old Faithful’s opening. He was able to pinpoint the exact location, within one or two meters, of where the boiling takes place in the chamber.
How Old Faithful works
Geysers are rare. There are only about 1,000 known in the world. Geysers need three things to work: a dependable supply of abundant groundwater, a geothermic heat source to warm the water, and an underground tank and pipe system that can trap steam bubbles until pressure forces it through to a hole in the ground.
After each Old Faithful eruption, the chamber never completely empties. A 15-minute refill period begins immediately after discharge. Then for the next 50 minutes, as water levels rise, seismic activity picks up when steam bubbles start filling the chamber. The bubbles oscillate water into the conduit, eventually leading to a violent steam explosion. The bubble trap in the larger cavern is what tourists experience when they hear Old Faithful gurgling before eruption.
Next for Vandemeulebrouck is a collaboration with the U.S. Geological Survey to study another Yellowstone National Park geyser called Lone Star.