[Geysers] Giant Sunday, July 23 (A true Mastiff Function?)

[Lynn Stephens]

David Monteith wrote the following about the July 23 eruption of Giant:

>Giant erupted today, Sunday July 23, at 1320.  The eruption came
>approximately 10 hours after an approximately 34 hour Grotto Marathon.  At
>the time of the expected Grotto re-start.

I think maybe what David meant to write was "At the time of the expected 
recovery hot period."
Following an approximately 34 hour marathon, I would not expect the Grotto 
restart for a LONG time.  Intervals following marathons are ROUGHLY twice 
the duration--i.e., after 24-26 hour marathons, the interval is about 45 - 
50 hours and after 30 - 33 hour marathons, have been about 58 - 60 hours.  
The marathon probably stopped somewhere between 3 and 4 am, so I would not 
have expected the next Grotto start until sometime on July 24.

I told several people that following an approximately 34 hour Grotto 
Marathon, the recovery hot period should probably wait until 10-12 hours 
after the end of the marathon, which put my window at 1pm - 3pm.  I believe 
a couple other people had put the window at noon - 2 pm for the window for 
the recovery hot period.


>The hot period was unusual.  Mastiff started erupting about 3 1/2 minutes
>into the hot period with both the front and back vents taking part.  The
>eruption reached 30 feet and lasted about 2 minutes.  At which point
>everything stopped.  Mastiff dropped a few inches below overflow and
>feather stopped (I can't remember what Tara said about Bijou but I think
>she said it was off.)

Bijou did turn back on for a brief time following the first eruption of 
Mastiff, then turned off again as the hot period restarted.


>For
>a while now, the behavior of the geysers along the line from Grotto to
>Oblong have been an excellent indicator of impending Giant eruptions.

The Oblong interval preceding this eruption was 5h34 minutes rather than the 
sub-4 hour interval it's had prior to several of the recent eruptions of 
Giant.

>Furthermore, this is the first Mastiff function I know of in
>the last 12 years that mimics the behavior reported by Marler in the final
>years of the 1950's activity.  In particular, the simultaneous eruptions of
>Catfish, Mastiff and Giant resulting in exemplary eruptions of all three.

I don't have my logbooks here with me, but I do have a photograph of Catfish 
(with the dual spires) from an eruption in either July or August 1997 when 
Mastiff and Catfish and Giant were erupting simultaneously in exemplary 
eruptions of all three.  (Even with my wide angle lens I couldn't get 
Catfish, Mastiff, and Giant in the same photo plus there was plenty of steam 
that morning.)  This eruption of Mastiff was taller than the 1997 eruption, 
but Mastiff was still hitting 50 feet and Catfish was between 30-35 feet and 
Giant was HUGE.  I'll have to check my logbooks, but I also believe I saw an 
April eruption in the 2000's with an "exemplary" eruption of Catfish and a 
50+ foot eruption of Mastiff.

Lynn Stephens

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