Old Faithful

Template:Short description Template:Other uses Template:Use mdy dates Template:Infobox hot spring Old Faithful is a cone geyser in Yellowstone National Park in Wyoming, United States. It was named in 1870 during the Washburn–Langford–Doane Expedition and was the first geyser in the park to be named.<ref>Template:Cite book</ref><ref name="tour"/> It is a highly predictable geothermal feature and has erupted every 44 minutes to two hours since 2000.<ref>Old Faithful Template:Webarchive, Geyser Observation and Study Association, August 17, 2011; Template:Cite web</ref> The geyser and the nearby Old Faithful Inn are part of the Old Faithful Historic District.

History

In the afternoon of September 18, 1870, the members of the Washburn-Langford-Doane Expedition traveled down the Firehole River from the Kepler Cascades and entered the Upper Geyser Basin. The first geyser that they saw was Old Faithful. Nathaniel P. Langford wrote in his 1871 Scribner's account of the expedition:

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In the early days of the park, Old Faithful was often used as a laundry: Template:Blockquote

Eruptions

File:OldFaithful.ogv

16-second video clip of an eruption

More than 1,000,000 eruptions have been recorded. Harry Woodward first described a mathematical relationship between the duration and intervals of the eruptions in 1938.<ref name=Woodward/><ref>Template:Cite web</ref> Old Faithful is not the tallest or largest geyser in the park; those titles belong to the less predictable Steamboat Geyser.<ref name="tour">Template:Cite web</ref> 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.<ref>Template:Cite web</ref>

Eruptions can shoot Template:Convert of boiling water to a height of Template:Convert lasting from 1½ to 5 minutes. The average height of an eruption is Template:Convert.<ref>Template:Cite book</ref> Intervals between eruptions have ranged from 34 to 125 minutes, averaging 66½ minutes in 1939,<ref name=Woodward>Template:Cite journal</ref><ref>Old Faithful Template:Webarchive, Geyser Observation and Study Association, August 17, 2011; Template:Cite web</ref> slowly increasing to an average of 90 minutes apart since 2000, which may be the result of earthquakes affecting subterranean water levels.<ref name="gosa">Template:Cite gosa</ref> The disruptions have made earlier mathematical relationships inaccurate, but have actually made Old Faithful more predictable in terms of its next eruption.Template:Citation needed After the Borah Peak earthquake in central Idaho in October 1983, the eruption intervals of Old Faithful were noticeably lengthened.<ref name=lmtwp84>Template:Cite news</ref>

File:Old Faithful eruptions graph.jpg

Waiting time between eruptions and the duration of the eruption for Old Faithful.

The time between eruptions has a bimodal distribution, with the mean interval being either 65 or 91 minutes, and is dependent on the length of the prior eruption. Within a margin of error of ±10 minutes, Old Faithful will erupt either 65 minutes after an eruption lasting less than 2½ minutes, or 91 minutes after an eruption lasting more than 2½ minutes.<ref>Template:Cite web</ref>

Measurement

Between 1983 and 1994, four probes containing temperature and pressure measurement devices and video equipment were lowered into Old Faithful. The probes were lowered as deep as Template:Convert. Temperature measurements of the water at this depth were Template:Convert, the same as was measured in 1942. The video probes were lowered to a maximum depth of Template:Convert to observe the conduit formation and the processes that took place in the conduit. Some of the processes observed include fog formation from the interaction of cool air from above mixing with heated air from below, the recharge processes of water entering into the conduit and expanding from below, and entry of superheated steam measuring as high as Template:Convert into the conduit.<ref>Template:Cite journal</ref>