A reduction in the geyser's water supply is causing the longer waits between eruptions.
Maybe they'll need to start calling it Old Fickle.
Yellowstone National Park's most famous geyser, Old Faithful, has been slowing down of late. In 1997, the geyser erupted on average every 71 minutes. In 2006, it erupted every 91 minutes. Shaul Hurwitz, a researcher with the US Geological Survey, has found that drought is to blame.
Working with Stanford University statistician Ashish Kumar and two scientists from the National Park Service, Mr. Hurwitz discovered that a reduction in the geyser's water supply is causing the longer waits between eruptions. Their study, published in the journal Geology, found that the length of the intervals may be influenced by the amount of water that has seeped into the geyser's underground plumbing system.
The amount of water in the system depends on rainfall. As a press release from the USGS puts it:
Multi-year precipitation records also strongly correlate with geyser behavior. Based on these results, the study proposes that an extended drought should result in longer intervals between eruptions, and perhaps even cessation of activity in some geysers. In contrast, in years with high precipitation, eruption intervals should be more frequent.