[Geysers] Fan and Mortar history

JEFFREY CROSS jeff.cross at utah.edu
Wed Dec 21 23:41:38 PST 2011

Why do people wait for Fan and Mortar?  Of the large geysers that erupt frequently enough to be seen, Fan and Mortar is the most difficult to observe, usually erupting once or twice a week.  Seeing an eruption is therefore a challenge.  Prior to the early 2000s, the hot periods showed an interesting progression that could stretch out for over an hour prior to the eruption, thus building suspense.  Because the eruption is spectacular, it's worth the wait.  I've heard Mortar's roaring eruption from a distance of 0.4 miles, and I have seen Fan's eruption throw water laterally to about 125 feet.  Brilliant rainbows are often visible in the spray during early morning eruptions.  With Mortar roaring loudly from its two large vents, and Fan spraying water in all directions, the entire river bank seems to be in eruption.

Of what significance is the activity of Fan and Mortar to our understanding of the Yellowstone hydrothermal system?  Probably the best way to study the hydrothermal system would be to monitor the flow of hot water from the system.  This has been done in Yellowstone by monitoring the flux of chloride out of the Park (Friedman and Norton in USGS Professional Paper 1717).  Chloride is abundant in hot spring water, but not in surface water, so chloride flux correlates with hot spring discharge.  Data on the eruptive frequency of individual geysers usually have too much natural variation to be useful.  If numerous geysers changed their activity at once, however, that would be significant.  Note, however, that Friedman and Norton made an interesting graph correlating the increasing interval of Old Faithful with an 11% decrease in hydrothermal output in the Park between 1983 and 2003.

Jeff Cross
jeff.cross at utah.edu

From: geysers-bounces at lists.wallawalla.edu [geysers-bounces at lists.wallawalla.edu] On Behalf Of Goh83642 at wmconnect.com [Goh83642 at wmconnect.com]
Sent: Wednesday, December 21, 2011 12:46 PM
To: geysers at lists.wallawalla.edu
Subject: Re: [Geysers] Fan and Mortar history

Hi Tara, Michael, and all you gazers,

   I have read a few of your logs and blogs about F&M and a question that
comes to me is:  Over the history of the past 650,000 years and the volcanic
activity of Yellowstone Park area, and the eons of time ahead of us, of what
importance is the 10, 15, 25 years of sparatic activity and history of one
geyser got to do with our knowledge or understanding of the region?  Other
than collecting and applying statistics to the historical data, will you,
with what probability, be able to predict the activity over the next 1, 5, 10
years or more?  What is the destination or goal of your study?

    I love Yellowstone Park, the geyser activity, the wildlife, the beauty
of the entire region.  I have visited the Park over 200 times in my fifty
plus years of "going to Yellowstone", follow the earthquake activity, winter
snow fall, webcams, etc., but can't for the life of me figure out why the
efforts that are put into tracking one F&M geyser?

   I would like to obtain more information as to the knowledge that is hope
to gain from all of this data?

   Gary Henderson - Meridian, Idaho</HTML>
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