[Geysers] Activity at Grotto/Giant, September 2-8

[Tara Cross]

This is the third and final installment of my reports on Giant.  Let's see if I can get through this one without any major omissions or errors....
 
The following is a summary of activity in the Grotto/Giant area prior to the September 8 Giant eruption.
 
Note:  I will be referring to the unnamed vent between Bijou and Catfish as "B-C Vent" in this report.
 
Grotto started a marathon at 2128e on August 31 that lasted through the day on September 1 for a total duration of 27h04m.  It was a bit early in the interval, but many were in the cage for the recovery hot period.
 
September 2
 
0032e Grotto marathon ended
1426 GHP, d=5m32s.  FS 5s, Mastiff surged up to 4 feet, India 98%.
 
Ever wonder what happens when Giant waits nearly 14 hours to have its recovery hot period but it's only 3 days into the interval?  Answer:  half of a good hot period.  There was some nice Mastiff surging and India was nearly covered, but Mastiff dropped at the 5-minute mark and that was that.
 
1723e Grotto, d=21m
1837ie Oblong
1918ie GHP, d>3m
2348e Grotto, marathon d=22h28m
 
September 3
 
Grotto was in marathon most of the day, but was found to be off by 2300; the electronic monitor put the end at 2216.
 
September 4
 
0421 Oblong
0602 GHP, d~9m.  FS 30s, Mastiff surged up to 4 feet, India 100%.
0855 GHP, d=3m20s.  FS active, Mastiff overflowed lightly.
0913 Oblong
1047 GHP, d=5m56s.  FS 20s, Mastiff briefly boiled to 3 feet but was mostly flat, India 70%.
1204 GHP, d=3m15s.  FS 30s, Mastiff overflowed lightly.
1321 Oblong
1322 Grotto Fountain
1324 GHP, d=7m50s.  FS 40s, Mastiff mostly flat, but surged up to 4 feet, Cave 4 inches, India 90%.
1348 Grotto, marathon d=17h21m
1420 Bathtub
1620 Bathtub
1722 Oblong
 
September 5
 
~0710 Grotto off
1413 GHP, d~15m50s.  FS 40s, Mastiff surged up to 4 feet, India 100%.
 
The recovery hot period included quite a bit of surging in Mastiff, up to about 9 minutes in, but it was up and down a lot and most of it wasn't wide.  Mastiff dropped shortly before the 10-minute mark, but Feather stayed on and there was some surging in Giant's cone, though the tallest surges were angled, and I was never optimistic that Giant might erupt.
 
After this, the real stupidity began....
 
1640 Oblong
~1755-1815 GHP, d=unknown.  Occurred between when I left Grand and when I arrived at Giant.
1944 GHP, d=7m51s.  FS 18s, Mastiff mostly flat but briefly to 1 foot, India 50%.
2138ns Oblong
2221 GHP, d=5m40s.  FS 45s, Mastiff overflowed lightly.
2316 Grotto Fountain
2325 Grotto, marathon d~5h
2336 GHP, d=1m48s.  Feather & SW Vents only, Mastiff did not overflow, SW Vents started 30s before Feather.
 
September 6
 
0037 GHP, d=8m25s.  FS ~4m, Mastiff surged at least 2 feet, Cave 2 inches, India 100%, SW Vents started before Feather; Feather restart lasted ~5m.
 
After the weak hot periods with longish durations, I was happy to see an actual strong hot period occur.  I did not stay out to see if Grotto would quit or continue; when I left at 0105, it was still going strong.  However, by the time Jim S. arrived at Grotto in the morning, it was off and the Giant Group was behaving as though there had been a marathon.  We ended up conjecturing that Grotto had lasted about 5 hours, which was confirmed later by the electronic monitor.  Given such a short duration, our expectations for the hot period were not high.
 
0654 GHP, d=8m40s.  FS active, Mastiff overflowed moderately.
0927 GHP, d=2m52s.  FS 50s, Mastiff overflowed lightly.
1025ie Oblong
1118 GHP, d=3m43s.  FS 15s, Mastiff boiled briefly to 1 foot, India 20%.
1252 GHP, d=8m45s.  FS active, Mastiff boiled briefly to 1 foot, India 20%.
1443 Grotto Fountain
1455 GHP, d=2m40s.  FS 1m05s, Mastiff overflowed lightly, SW Vents started before Feather.
1458 Grotto, marathon d=10h23m
1508 Oblong
1602 GHP, d=2m45s.  Feather & SW Vents only, Mastiff overflowed lightly, SW Vents started before Feather.
1726 GHP, d=6m50s.  FS 4m18s, Mastiff overflowed moderately, Cave 3 inches, India 70%.
1939ie Oblong
 
A couple of things struck me about the hot periods we saw.  Feather was very strong, and Feather Satellite was coming on in nearly all hot periods, even those with short durations.  Meanwhile, Mastiff did almost nothing but gently overflow, and nothing was seen out of Cave until the final hot period going into the marathon.  The two hot periods that surpassed 8 minutes in duration had no business doing so; Mastiff was basically drooling while Feather and Feather Satellite merrily continued to erupt at full strength.
 
Simply put, the hot periods did not resemble anything I have seen lead to eruptions in the past, and it seemed that the system was just wasting energy.  As Kitt put it, it was stuck in "Feather Function."  And, adding to our frustration was miserable weather--the entire day was cloudy and cold with occasional rain.  We hoped for better weather the next day at the very least....
 
September 7
 
~0121 Grotto off
0839 GHP, d=4m02s.  FS 20s, Mastiff overflowed moderately.
0849 Oblong
1038 GHP, d=8m40s.  FS 13s, Mastiff mostly flat but boiled up to 2 feet, India 80%.
1145 GHP, d~4m.  FS active, Mastiff boiled to 1 foot.
1256 GHP, d=1m18s.  Feather & SW Vents only, Mastiff did not overflow, SW Vents started before Feather.
1259 Oblong
1354 Grotto Fountain, d=30m
1355 GHP, d=8m10s.  FS 50s, Mastiff overflowed moderately, Cave 4 inches, India 70%, B-C Vent active.
1410 Grotto, marathon d~17h
 
The hot period that coincided with the start of Grotto gave some reason to hope that Giant was going to get out of its funk.  Mastiff still didn't do much boiling, but it did cover India 70%, and Cave boiled vigorously to 4 inches.  Bijou came on about 20 seconds before Feather quit, along with splashing from the B-C Vent.  Feather was off for 1m28s and then came back on for a restart lasting ~4 1/2m; however the surging in Giant's cone wasn't impressive.
 
After four consecutive marathons we were hoping that Grotto would actually manage to have a short eruption, but once again it continued to erupt into the evening as activity at Giant weakened.
 
1456 GHP, d=2m.
1608 Bathtub
1629 Oblong
1729 GHP, d=4m34s.  FS active, Mastiff boiled 6 inches, India 10%.
 
That evening I received a phone call from Kitt Barger, who said she was planning to get her hair done in Billings the next day.  I told her that the hair could wait--we needed her to come fix Giant.  So, she loaded the Suburban and headed in to the park....
 
September 8
 
Everyone was relieved at dawn to hear that Grotto was still erupting, but then Kitt estimated the Grotto stop time at ~0715.  We'd all been hoping for a longer duration, but once again we gathered in the cage for the recovery hot period.  By about 1230 the GIP had started to have strong cycles up past the "elbow," and by 1330 Bijou was having thicker splashes after these cycles.
 
Then Cynthia Barwin started calling events at Fan & Mortar, so I migrated that way.  Others went to wait for Oblong, which erupted at 1501.  At Fan & Mortar, after a Gold pause that turned out to be 57 minutes long, High and Gold came on very strong, and more gazers came down.  I was just thinking to myself that the water levels were holding after 10 minutes when things suddenly became rather complicated--Lynn Stephens called that there was water rising in Mastiff.
 
This presented those of us at Fan & Mortar with the dilemma of deciding when to give up and head to Giant.  The water levels were still good when Lynn called the start of the hot period at 1520.10.  In the first 2 minutes of the hot period, Lynn was calling that Mastiff was boiling 1-3 feet, but the water levels were still good at Fan & Mortar.  Then, within a matter of seconds, Lynn called that Mastiff was getting wide and to 4 feet, and we saw steam in Gold Vent.  Cynthia and I looked at each other with the same expression--ABANDON SHIP!!!!
 
We raced up the hill as Lynn continued to call good surging in Mastiff.  I arrived at Giant, huffing and puffing, at about 4 1/2 minutes into the hot period, and Mastiff was flat but still overflowing heavily.  Then, 6 minutes into the hot period, Mastiff started boiling again, first to 1-3 feet, then wider with several surges to 4 feet.  Turtle was boiling to 4-6 inches.  Mastiff was up and down a bit, but the overflow never subsided, and at the 9-minute mark the surging was reaching 6-8 feet with heavy runoff.  After some sustained surging to the height of the cone, the back vent of Mastiff joined in, and Mastiff was in full eruption at 1530.12.  Just as Mastiff was taking off Bijou came on, along with the B-C Vent, and then went into roaring steam.
 
Both Vents of Mastiff erupted to 20-30 feet for a few seconds, but then the front vent stopped and the back vent took over.  The wind was blowing the steam towards the Purple Pools, providing excellent viewing for Mastiff.  The back vent continued to erupt by itself until the front vent joined in again, and Giant began to have cone-filling surges.  Just as Giant was starting, both vents of Mastiff were erupting powerfully to 20-30 feet.
 
The water burst up in Giant's cone at 1532.15, then rocketed into the air with a loud whooshing sound, soon accompanied by the sound of crashing water.  The column was lit by the afternoon sun as it towered above us against a blue sky.  Due to the wind direction, Giant's water did not hit the cage directly; it landed just to the right.
 
Mastiff continued to erupt for about 2 minutes after Giant started, and Catfish started at 1533.56 and erupted to 15-20 feet for several minutes before going into steam.  I don't know when Turtle started, but it was in eruption to about 3 feet when the initial curtain of steam and water had dissipated after Giant's start.
 
I will admit, I did look over my shoulder to see if there was a steam cloud rising from the area of Fan & Mortar, but I've never been happier to see that it didn't erupt.  Soon after the start of Giant, a thin cloud layer covered the sun, but a rainbow was still visible in the spray from the boardwalk towards Oblong.  The eruption lasted 98 minutes.
 
Special thanks to Kitt for fixing Giant for us.  I've really had quite enough of mini-marathons....
 
--Tara Cross
fanandmortar at hotmail.com
 
 
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