[Geysers] What is Grand's Shortest Interval?

[Mary Beth Schwarz]

     A Report on Grand Geyser by John R. Railey for observations of 41
eruptions from 4 June through 30 June, 1977, mentioned a minimum interval
of 4h 15m 50s.  In the list of 71 eruption intervals (assumed either for
June or for the 4th-30th of June) added at the end of the report (but
stated not a part of the report), the only one listed that is below 6 hours
is 4h 55m 20s, so there may be typos in one of these.  This was the report
in which John Railey suggested widening the boardwalk at Grand for safety
and adding benches such as those at Castle Geyser.  The 1977 log book may
have the times for this short interval, but I have not yet checked.  During
summer 2012 I mentioned this short interval to people who have watched
Grand for many decades, and none of them knew of a shorter one.  Items in
Railey's June 1977 report include:

     Minimum interval                           4h 15m 50s  (or was it 4h
55m 20s??)

     Maximum interval                          8h 22m 5s

     Average interval                            8h 22m 5s

     Average number of bursts              2.80

     Average total duration                   12m 33s

     1 burst                                         1

     2 burst                                         14

     3 burst                                         19

     4 burst                                         6

     5 burst                                         1



     The wide variation in intervals that Grand can have is the reason we
__always__ check visually to see whether there has been a recent eruption
(or oops, it can be seen erupting now!) when someone reports an eruption
time of Grand or any other geyser.  For Grand it is easy to see the
eruption or the evidence of the empty pool and perhaps Turban and Vent
erupting afterwards.  You may say "It usually does not do this now" if you
must, but GO CHECK the geyser to be certain it did not do something
different from what you have seen.  Grand can have an isolated shorter
interval or totally change intervals very quickly.

     The 1959 Electronic/2001 visual by Jeff Cross on 7 October 2012 is odd
because the electronic sensor at Grand usually has a __delay__ of 2-5m in
recording the eruption times, so it is indeed difficult to reconcile.  The
1459 time for Grand on Oct. 7 was a gazer visual.

     GeyserTimes shows another short interval of Grand on 12 October 2012
between 0014E and 0514E.

     The only different thing seen during these very short intervals of
Grand in August-October 2012 is that the time between the first overflow of
Grand and the eruption is shorter than usual.  Past "safe" times when Grand
would not erupt after the first overflow were about 2h to 2h15m, but we saw
one eruption on 1 September that was only 65 (thanks Mike Keller for the
first overflow time) minutes after the first overflow.  Since we went out
by 4.5 hours after the previous eruption we sometimes saw the first
overflows as well as the eruption.  In summer 2012 the first overflows were
about 4h-4.5h.

     On a different subject, Roderick Hutchinson used to say that the
response of some of the geysers to some earthquakes was often about 10 days
(or was it 7-10?) rather than immediately (an exception being the nearby
large Hebgen Lake earthquake with the sudden changes).

     Thanks for all the observations, Electronic times, and webcam times
posted on geysertimes.org so we can still have some idea of what the
geysers are doing!

     Mary Beth Schwarz
     schwarzmb at gmail.com

On Wed, Oct 17, 2012 at 12:41 AM, JEFFREY CROSS <jeff.cross at utah.edu> wrote:

>  What is the shortest interval of Grand ever noted?
>
> I have one candidate, as follows:
>
> 07 October 2012
> Grand 1459
> Grand 2001, I = 5 hours 2 minutes
>
> The geysertimes record shows the second eruption occurring at 1959, which
> would make a 5 hour interval exactly.  However, I cannot reconcile the 2
> minute difference between this time and my own observation, as I was
> passing Belgian Pool when Grand began.
>
> Jeff Cross
> jeff.cross at utah.edu
>
> _______________________________________________
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> Geysers at lists.wallawalla.edu
> 
>
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