<p>From <a href="http://en.wikipedia.org/wiki/Old_Faithful">wikipedia</a>:</p>

<blockquote>
  <p>With a margin of error of 10 minutes, Old Faithful will erupt 65 minutes after an eruption lasting less than 2.5 minutes or 91 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</p>
</blockquote>

<p>Relatively <a href="http://blogs.agu.org/geospace/2013/04/12/newfound-chamber-below-old-faithful-may-drive-eruptions/">recent discoveries</a> led scientists to believe that there is a substantial underground chamber where the water and steam build up:</p>

<blockquote>
  <p>A previously unknown underground cavity might help trigger the timely eruptions of the famous Yellowstone geyser Old Faithful, a new study shows. The researchers who uncovered new evidence of a chamber suspect that it stores the pressurized near-boiling water, steam, and other gases that propel Old Faithful’s eruptions.</p>
</blockquote>

<p>Are the 65 minute and 91 minute values given for the eruption times simply a byproduct of needing more time for the steam to "recharge" after a larger eruption, or is there a deeper interplay between the underground cavity and the main channel that causes some sort of a vortex that has a (somewhat) regular periodicity?</p>

CC BY-SA 3.0
2014-08-21T06:17:57.167Z
I'm a rank amateur in this area, so if I have abused terminology, please let me know!
jonsca
CC BY-SA 3.0
2014-08-21T14:25:46.210Z
Welcome to the site! This is one of the best questions I have seen on here. Very interesting. My first guess would be that since the more-time-to-recharge hypothesis could basically give you a linear model, the distribution it would produce would be more or less normal, not bimodal. There's likely something more interesting going on here. The process makes me think of the bimodal patterns that [water flow forms make](http://youtu.be/GkNtarWFtik?t=41s). Could be a similar process, but with 2 unequal sized side cavities. But this is speculation on my part, I have no experience in the area :)
naught101
<geophysics><hydrology><geysers>
Is the cause of Old Faithful's bimodal distribution for eruption times straightforward?
jonsca
# Is the cause of Old Faithful's bimodal distribution for eruption times straightforward?

(Asked by: username_0 on 2014-08-21)

From [wikipedia](http://en.wikipedia.org/wiki/Old_Faithful):

> With a margin of error of 10 minutes, Old Faithful will erupt 65 minutes after an eruption lasting less than 2.5 minutes or 91 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

Relatively [recent discoveries](http://blogs.agu.org/geospace/2013/04/12/newfound-chamber-below-old-faithful-may-drive-eruptions/) led scientists to believe that there is a substantial underground chamber where the water and steam build up:

> A previously unknown underground cavity might help trigger the timely eruptions of the famous Yellowstone geyser Old Faithful, a new study shows. The researchers who uncovered new evidence of a chamber suspect that it stores the pressurized near-boiling water, steam, and other gases that propel Old Faithful’s eruptions.

Are the 65 minute and 91 minute values given for the eruption times simply a byproduct of needing more time for the steam to "recharge" after a larger eruption, or is there a deeper interplay between the underground cavity and the main channel that causes some sort of a vortex that has a (somewhat) regular periodicity?

**Tags:** geophysics, hydrology, geysers

> **Comments:**
> **username_0**: I'm a rank amateur in this area, so if I have abused terminology, please let me know!  
> **username_1**: Welcome to the site! This is one of the best questions I have seen on here. Very interesting. My first guess would be that since the more-time-to-recharge hypothesis could basically give you a linear model, the distribution it would produce would be more or less normal, not bimodal. There's likely something more interesting going on here. The process makes me think of the bimodal patterns that [water flow forms make](http://youtu.be/GkNtarWFtik?t=41s). Could be a similar process, but with 2 unequal sized side cavities. But this is speculation on my part, I have no experience in the area :)  

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## 0 answers

