[Geysers] Response to dating geyser water

[TSBryan at aol.com]

Back about a month ago, we learned of the publication of a paper titled  
"Climate-induced variations of geyser periodicity in Yellowstone National Park,  
USA", authored by Hurwitz, Kumar, Taylor and Heasler. The appearance of that  
paper, and discussions resulting from that, read (in essence): "How do they 
date  geyser water, and where did the figure of '500 years' come from."
 
Via Ralph Taylor, co-author Hurwitz provided an answer, namely: "  In short 
answer to...[the] question ... 'OF's water supply is about 500 years  old' -- I 
don't know how that info came about." 
 
Well... since my book(s) would seem to be one source of the "500  years" 
statement, a huge exclamation point could be part of my answer  to Hurwitz. I have 
held this response for my return to my full library here in  Arizona.
 
In my short answer, check USGS publications by such rather well-known  
authorities as Truesdell, Fournier, Christensen, and White.
 
A primary source, which I cite here, is:
Rye, R. O. and Truesdell, A. H., 1993, The question of recharge to the  
geysers and hot springs of Yellowstone National Park, USGS Open-File Report  93-384.
 
I acknowledge first that a complete lack of detectable tritium in  water 
shows only that it is "older" than 60 years. (Well, the paper in question  here 
seems to say 50 years while all these other USGS things say 60 -- but  what's 
20% or so when the authors admit they "enhance the signal-to-noise ratio"  by 
"filtering [to eliminate] 15% of the [Old Faithful] intervals from the data  
set" -- as several people versed in math and statistics, as well as geysers,  
said upon seeing that: "WHAT!?!?!")
 
Sorry, I digress... In the Rye and Truesdell article are the following  items 
(as samples):
 
-- the deep reservoir residence time of most of the thermal water "should"  
be less than 1900 years
 
-- the discharge from the deep reservoir is [approximately] 7.5 X 10^10  
kg/yr, and per the chloride inventory the residence time is between 370 and 1900  
years.
 
-- the above is consistent with water-rock reactions AND with a recoil  model 
for radium isotope supply that yields a maximum of 1150 years. {NOTE: It  is 
in another paper that unfortunately I am unable to locate at the moment in  
which Friedman states that this value is a "best guess figure" for recharge  
rate.}
 
-- However, the above authors note that, if the deep reservoir is  
replenished from multiple sources, then the oldest deep geothermal component(s)  could 
well be as "old" as 10,000 years.
 
-- Finally, the authors hypothesize that there could well have been a major  
influx of water to the geothermal system during the "Little Ice Age" of the 
15th  century -- that is, at a time somewhat more than... errr... 500 years  ago.
 
I will also point out to the authors that they apparently missed one  
reference to the matter of surface water influences, supporting my initial  reaction 
to the article of : "Duh." This is:
Marler, G. D., 1964, Seasonal changes in ground water in relation to hot  
spring activity; Am. Jour. Sci, v.262, May 1964, p.674-685.
 
Enjoy.
 
T. Scott Bryan



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