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 <a href="http://geysertimes.org">geysertimes.org</a> so we can still have some idea of what the geysers are doing! Mary Beth Schwarz <a href="mailto:schwarzmb@gmail.com">schwarzmb@gmail.com</a> <div class="gmail_quote">On Wed, Oct 17, 2012 at 12:41 AM, JEFFREY CROSS <<a href="mailto:jeff.cross@utah.edu" target="_blank">jeff.cross@utah.edu</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> <div> <div style="direction:ltr;font-size:10pt;font-family:Tahoma">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 <a href="mailto:jeff.cross@utah.edu" target="_blank">jeff.cross@utah.edu</a> </div> </div> _______________________________________________ Geysers mailing list <a href="mailto:Geysers@lists.wallawalla.edu" target="_blank">Geysers@lists.wallawalla.edu</a> <a href="https://lists.wallawalla.edu/mailman/listinfo/geysers" target="_blank">https://lists.wallawalla.edu/mailman/listinfo/geysers</a> </blockquote></div>