Editing Old Faithful (section)

==Eruptions==
[[File:OldFaithful.ogv|thumb|left|16-second video clip of an eruption]]
More than 1,000,000 eruptions have been recorded. [[Harry Woodward (naturalist)|Harry Woodward]] first described a mathematical relationship between the [[Time|duration]] and [[interval (time)|intervals]] of the eruptions in 1938.<ref name=Woodward/><ref>{{cite web |url=http://www.nps.gov/yell/historyculture/arch_interp.htm |title=Season Report on the Naturalist Activities at Old Faithful Station |year=1939 |first= Harry R. |last=Woodward}}</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">{{cite web |title=Old Faithful Geyser |work=Old Faithful Area Tour |publisher=National Park Service |url=http://www.nps.gov/yell/learn/photosmultimedia/webcams.htm}}</ref>  The reliability of Old Faithful can be attributed to the fact that it is not connected to any other thermal features of the [[Geothermal areas of Yellowstone|Upper Geyser Basin]].<ref>{{cite web |title=Old Faithful slows, but grows |first= Michael| last= Milstein|work=The Billings Gazette | date=  September 14, 1999| url= http://www.billingsgazette.com/wyoming/990914_wyo01.html |access-date=July 21, 2007 |archive-url= https://web.archive.org/web/20071009200545/http://www.billingsgazette.com/wyoming/990914_wyo01.html |archive-date= October 9, 2007}}</ref>

Eruptions can shoot {{convert|3700|to|8400|USgal|L}} of boiling water to a height of {{convert|106|to|185|ft}} lasting from 1½ to 5 minutes. The average height of an eruption is {{convert|145|ft}}.<ref>{{cite book |last = Chapple|first = Janet|title = Yellowstone Treasures|publisher = Granite Peak Publications|year = 2013|location = Lake Forest Park, WA|page = 79|isbn = 978-0-9706873-8-8}}</ref> Intervals between eruptions have ranged from 34 to 125 minutes, averaging 66½ minutes in 1939,<ref name=Woodward>{{cite journal |journal=Northwest Science |title=Old Faithful, An Example of Geyser Development in Yellowstone Park |volume=13 |year=1939 |pages=50–5 |first1=Clyde Max |last1=Bauer |first2=George |last2=Marler |url=http://www.vetmed.wsu.edu/org_nws/NWSci%20journal%20articles/1927-1939/1939%20vol%2013/13-2/2008-02-11/v13%20p50%20Bauer%20and%20Marler.PDF |url-status=dead |archive-url=https://web.archive.org/web/20110610041553/http://www.vetmed.wsu.edu/org_nws/NWSci%20journal%20articles/1927-1939/1939%20vol%2013/13-2/2008-02-11/v13%20p50%20Bauer%20and%20Marler.PDF |archive-date=June 10, 2011 |df=mdy-all }}</ref><ref>[http://www.geyserstudy.org/geyser.aspx?pGeyserNo=OLDFAITHFUL Old Faithful] {{Webarchive|url=https://web.archive.org/web/20120221235615/http://www.geyserstudy.org/geyser.aspx?pGeyserNo=OLDFAITHFUL |date=February 21, 2012 }}, Geyser Observation and Study Association, August 17, 2011; {{Cite web|url=https://www.nps.gov/features/yell/webcam/oldFaithfulStreaming.html|title=National Park Service Webcam|website=www.nps.gov|access-date=January 1, 2017}}</ref>  slowly increasing to an average of 90 minutes apart since 2000, which may be the result of [[earthquake]]s affecting subterranean water levels.<ref name="gosa">{{cite gosa|OLDFAITHFUL|Old Faithful|archive-url=https://web.archive.org/web/20191024141724/http://www.geyserstudy.org/geyser.aspx?pGeyserNo=OLDFAITHFUL|archive-date =October 24, 2019}}</ref> The disruptions have made earlier mathematical relationships inaccurate, but have actually made Old Faithful more predictable in terms of its next eruption.{{citation needed|date=September 2017}} After the [[1983 Borah Peak earthquake|Borah Peak earthquake]] in central [[Idaho]] in October 1983, the eruption intervals of Old Faithful were noticeably lengthened.<ref name=lmtwp84>{{cite news |url=https://news.google.com/newspapers?id=W4RfAAAAIBAJ&pg=3884%2C2019027 |work=Lewiston Morning Tribune |location=(Idaho) |agency=(Washington Post) |last=Reid |first=T.R. |title=Idaho quake upsets, yet befriends Old Faithful geyser |date=October 7, 1984 |page=5E}}</ref>

[[File:Old Faithful eruptions graph.jpg|thumb|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>{{cite web |title=Video: Predicting Old Faithful |url=https://www.nps.gov/yell/planyourvisit/geyser-activity.htm |website=National Park Service}}</ref>