The eruptive fury of Yellowstone National Park's geysers, those wonderful spouters of steam and hot water, seems to be determined by annual precipitation in the park, according to a study published in the June issue of the journal Geology.

Geysers are rare hot springs that periodically erupt bursts of steam and hot water. Old Faithful has remained faithful for at least the past 135 years, showering appreciative tourists every 50 to 90 minutes (most recently an average of 91 minutes).

USGS researcher Shaul Hurwitz and his colleagues from Stanford University and Yellowstone have discovered that changes of water supply to a geyser’s underground plumbing may have a large influence on eruption intervals. For example, geysers appear to lengthen and shorten their intervals on cycles that mimic annual dry and wet periods.

According to the researchers, 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.

Geysers are extremely rare; perhaps fewer than 1,000 exist worldwide, with more than half of them in Yellowstone. The famous Old Faithful Geyser was named in 1870 during the Washburn-Langford-Doane Yellowstone expedition and was the first geyser in the park to be named. Old Faithful eruptions can be viewed on any computer on Earth via a video camera deployed by the National Park Service.

Instrumental data that records geyser eruption times is available at this site. Additionally, long-term meteorological trends can be inferred from seasonal streamflow trends like those in the Madison River.