[Geysers] Activity at Giant/Grotto, Aug. 24 & 25

[Tara Cross]

This is the first in a series of 3 reports on the Giant eruptions that occurred during my 2-week visit to the park.  My apologies for the lateness of these reports.
 
First, a few notes: 1.  I realized that I have not been extending the proper thanks to other gazers who have spent many hours at Giant and Grotto and called hot periods at Giant at all hours of the day and night.  So THANK YOU to all, and especially Lynn Stephens, Jim S., the Strassers, Scott Bryan, and Kitt Barger.
2.  A couple of general observations that seemed to differ from what I'd seen previously this summer:  I noticed that Oblong was correlating to Giant hot periods more often than before, so I included Oblong times in this summary.  Also, I did not see a single solo Grotto Fountain eruption in the two weeks that I was in the park; these had been quite common following Grotto marathons in July and August. 
3.  Some of my hot period notes have gotten rather long, so for this report I will be using some abbreviations, listed below: GHP - Giant hot periodFS - Feather Satellite; then now long after Feather it started
  The following is a summary of activity at Giant/Grotto leading up to the August 25 Giant eruption.
As previously reported, Grotto started a marathon on August 23 at 1437 that lasted approximately 15h15m (the visual estimate for the stop time was 0500; the electronic monitor put it at 0552).
 
August 241327 GHP, d=10m31s.  FS 25s, Mastiff surged 5 feet, India 100%, restart lasted ~5m.
 
I didn't actually see the entirety of this hot period, as I was literally just getting to the bike rack upon arrival at Old Faithful when it started.  Based on the radio calls, it sounded like the Mastiff surging was getting some height, but was never sustained.  Obviously the outcome of the hot period was disappointing, but Giant has only once since April 2006 erupted after a marathon of less than 17 hours, and the recovery time of ~7.5 hours was also not terribly long.
 
Since there had been a string of 5 consecutive mini-marathons, we weren't sure what to expect next, but when the next Grotto eruption was short, we knew there was a chance for the energy to shift to the South side of the platform.  The rest of the days' events were as follows:
 
1721 GHP, d=3m57s.  FS 30s, India 40%.
1845 GHP, d=7m53s.  FS 30s, Mastiff mostly flat but 1-2 feet at times.
1936 Grotto Fountain, d=33m
2004 Grotto, d=24m
2012 GHP, d=2m25s.  Feather & SW Vents only, Mastiff overflowed lightly.
2019 Oblong
2127 GHP, d=1m10s.  Feather only.
2240 GHP, d~8m.  FS active, India 100%, Cave 4 inches.
 
This was a strong-ish hot period, but not strong enough to make me feel comfortable leaving Giant for the night.  So, Kitt Barger, Andrew Bunning, Jeff Cross, and I prepared to wait through the night.
 
Based on the 24 minute duration of Grotto, the next eruption should have taken place around midnight.  At 2330, I checked on the Grotto area and found South Grotto Fountain having a series of eruptions lasting roughly 1 minute and reaching 6-8 feet high.  I'm not sure how long this lasted, but they were over by 0025.  Therefore, South Grotto Fountain did not have a sustained series of full eruptions like it has prior to other South function eruptions.  However, the result was the same--a sizeable delay for Grotto.
 
August 25
 
0017 GHP, d~3m.  FS active.
0035 Oblong
0136 GHP, d~3m.  Feather & SW Vents only.
0231 GHP, d~6m.  Feather & SW Vents only.
0322 GHP, d~1m50s.  Feather & SW Vents only.
0324 Grotto Fountain
0329 Grotto, d=28m
0418 GHP, d=2m30s.  FS 55s, Mastiff overflowed lightly.
 
None of these hot periods expended much energy, and all started with the SW Vents prior to Feather.  The moon set around 0400, and at 0515 we started to see the barest hint of dawn over the ridge to the east, though it was no help for seeing anything.  Kitt was over at Oblong when I heard the SW Vents sputtering, and we all scrambled to our feet and grabbed our flashlights for the next hot period.
 
Feather started at 0517.57 (my radio call had it at 0518, since I was fumbling with radio, watch, and flashlight, but Andrew got the exact time), and for the first several mintues, the hot period looked the same as the previous ones; just Feather and SW Vents and light overflow with a little boiling from Mastiff.  Then, around the 4-minute mark, Feather Satellite and Rust joined in, and Mastiff began to surge.  The tallest surges I saw (given poor viewing conditions) were about 4 feet high, and we could hear a significant increase in overflow.  Around 6 minutes into the hot period, Cave was boiling vigorously to 4 inches and India was about 95% covered.
 
It was too steamy to see when Mastiff dropped, but Cave's water level dropped and we saw Feather weakening before it shut off.  The hot period duration was roughly 7m20s (I was running a stopwatch).  When Feather had not restarted after 30 seconds, I figured that Giant had decided to cooperate and wait for daylight.  Then, just as I was going to my backpack to gather my things, Giant had a thin, sustained vertical surge to nearly the height of the cone.  And then another.  Then Feather restarted, at least a full minute after it had stopped, and the surging got thicker.
 
I called on the radio that Feather had restarted but Feather Satellite was not on, and in fact the restart didn't look that great except that there were huge vertical surges in Giant's cone.  At that point we all scrambled to get out of the cage and into rain gear, and Jim S. quickened the pace as he hurried down from Grand.  The surges continued to build in strength until they were nearly twice the height of Giant's cone, but I was still in a state of disbelief when I blurted "Giant is...starting?!?" into the radio at 0528.  Dave Whinery later said my voice sounded half surprised, half apologetic.  I know that Giant has erupted from a Feather restart at least 6 times during this active phase, but it was a first for me, and I had not heard of it erupting after Feather had been off for more than 20-30 seconds.
 
Giant's column shot into the dark sky in a series of surges that got progressively higher and higher, lit by our flashglights.  We got a glimpse of it at full height before it became enveloped in steam and a thick curtain of crashing water swallowed the cage.  Within a few minutes, I noticed that my poncho was stuck to itself with ice, and ice was forming on the boardwalk, extending from Grotto to the 200-foot marker towards Oblong.  Gradually we began to see without our flashlights, and we kept slipping and sliding back and forth trying to view Giant's water.  The sunrise lit the few clouds in the sky a pale pink color, but of course I didn't have my camera.  Towards the end of the eruption we started to see the morning joggers coming by in their shorts; it made me cold just to look at them (I didn't start to warm up until I biked back to Hams).
 
The duration of the eruption was 102 minutes.
 
--Tara Cross
fanandmortar at hotmail.com
 
 
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