Old Faithful Geyser
The Old Faithful Geyser, located in Yellowstone National Park, is perhaps the world's most famous geyser. The geyser was named in 1870. An eruption can shoot ~32,000L of boiling water to a height of 56.1m. More than 137,000 eruptions have been recorded, lasting from ~1.5-5.5 minutes, with intervals ranging ~30-120 minutes. Harry M. Woodward first described a mathematical relation between the duration and intervals of the eruptions (1938).
Over the years, the length of the intervals has increased; possibly the result of earthquakes affecting subterranean water levels. These disruptions have made the earlier mathematical relation inaccurate, but have in fact made Old Faithful more predictable. With an error of 10 minutes, Old Faithful will erupt 65 minutes after an eruption lasting less than 2.5 minutes or 92 minutes after an eruption lasting more than 2.5 minutes. The reliability of Old Faithful can be attributed to the fact that it is not connected to any other thermal features of the Upper Geyser Basin.
