[Geysers] July 3 Giant details - Part 2

[Tara Cross]

A message from Tara Cross <fanandmortar at hotmail.com>


Part 2 - Activity at Grotto/Giant on July 3 prior to the eruption


After major storms moved through overnight, gazers were not eager to get up in the cloudy dawn to check Giant.  The first person to venture down-basin was Thomas Barger, who at 0700 reported that Grotto was off and Giant had not erupted overnight.  From this time on, gazers observed a lot of weird activity in the Giant/Grotto area.  There are a lot of details; I will try to report them as fully and accurately as possible.

After his initial reports, Thomas stayed in the Grotto area.  Since we did not know what Grotto had done overnight, we could only guess that Grotto might be getting close to erupting, because at 0711, Thomas reported that Grotto Fountain was overflowing and boiling.  Then he called South Grotto Fountain at 0714, and it quickly became apparent that something wasn't right.  Spa had risen to overflow after Thomas's arrival, and he saw it have one burst to 5 feet at 0715.

>From that time on, Spa was full and pulsating, and South Grotto Fountain continued to erupt at intervals of 7-15 minutes (except once when it had a 30-minute interval).  When Dave Monteith arrived, he noted that Grotto Fountain was overflowing when South Grotto Fountain was not erupting, and at these times the Indicator Spring was also high.  The water level in Grotto Fountain and the Indicator Spring would begin to drop before the eruption of South Grotto Fountain began, and likewise begin to rise before South Grotto Fountain had ended.  The Indicator Spring never dropped more than 4 inches.  Grotto Fountain put out enough water to fill its runoff channel for most of the day.

Thomas called the first observed hot period of the day at 0737, which lasted 8m15s and covered 85% of India.  Mastiff surged to as much as 5 feet, but the thing that got us really interested was that Cave vent had a full eruption to 3 feet starting about 4 minutes into the hot period.  This was a fairly major change from the hot periods seen in the previous week; Cave had never done more than bubble to a few inches.  After the hot period, Dave and Thomas returned to wait for Grotto Fountain.  Oblong erupted at 0814, and at 0934 Skip Manry observed a bathtub at Giant.  After this, most gazers moved to either Grand or Beehive--it took us a while to figure out that things weren't just weird at Grotto, they were weird at Giant, too.

After the bathtub, Bijou came on very strong with mixed water and steam, and Mastiff was depth charging energetically.  From 1000 on, Dave and Thomas observed that there was occasional gurgling in Grotto, and sometimes a visible splash or two.  Then gazers at Grand noticed that Bijou was off, and Thomas called that Feather was i.e. at 1029.  The duration of the hot period was at least 3 minutes, but from Grand it appeared that Mastiff never got higher than 1 foot.

After Grand, many gazers moved to Geyser Hill to wait for Beehive, leaving only Dave and Thomas in the Giant/Grotto area.  Around 1100 there was another boiling episode in Grotto Fountain, but it did not lead to anything.  Then at around 1135 Thomas noticed that Bijou was off and rushed over to Giant.  When he arrived, Feather had already shut off.  He reported that India was about 75% covered, and then called a Feather restart at 1140.  The restart was short, but Giant had a vertical, cone-filling surge--in fact, it was so large that Dave could see water over the top of Giant's cone from where he was standing at Grotto Fountain.  The duration of the hot period remains a mystery, but it couldn't have been more than 5 mintues or so, because Dave and Thomas had been keeping an eye on Bijou.

Despite this big hint that we should be watching Giant closely, we still hadn’t quite caught on to the fact that there were hot periods occurring hourly at Giant.  So, after gazers returned to Giant from Beehive, Feather was once again seen i.e. at 1238 by Julie Thomson, who was hurrying to Oblong.  She saw the high water in the GIP as she passed by and called the hot period in progress, so the duration was unknown.  Based on the lack of overflow from Mastiff, it was probably in the 1-3 minute range.

After the hot period I went to Oblong and watched a fill, then returned to Grotto Fountain where it was still having its back-and-forth battle with South Grotto Fountain.  From this time on I was watching Bijou carefully, and it continued as it had been all morning--erupting powerfully with mixed water and steam.  As I was hoofing it back to Oblong for the next fill, I took one more glance at Bijou and saw that it was off.  So, I did a U-turn back to the Giant platform to find water rising in Mastiff.  The Southwest Vents began at 1338.40, and Feather began at 1339.18.  Mastiff boiled to a few inches and put out a tiny bit of overflow.  The duration was 2m10s.  Afterwards, the powerful Bijou and depth charging in Mastiff resumed.

Oblong had also erupted at 1338, so I went back to Grotto Fountain, where there was a boiling episode at around 1400, but once again, nothing further happened.  With the next Bijou pause, water was rising in Mastiff again.  The Southwest Vents started at 1440.45 and Feather was on at 1441.15.  Mastiff boiled to about 6 inches and put out a small amount of overflow that barely trickled off of the platform.  Cave bubbled to about 3 inches.  The duration of Feather was 4m33s.

I went back to Grotto Fountain and watched yet another boiling episode around 1520, and once again it cycled back down without erupting.  Just about the time I was thinking that it was time to return to Giant for the next hot period, I noticed from Grotto that Bijou had paused.  As I hurried towards Giant, gazers waiting at Giant were surprised to see a sudden surge from Mastiff.  It appeared to come mainly from the back vent and was sustained to half the height of Giant's cone for at least 5-7 seconds.  Kitt Barger described it as a white wall of water 6-8 feet wide and 4-5 feet tall, holding there long enough for her to spring up from a reclined position and observe it before the water level dropped again.  Her comment afterwards was, "I thought Mastiff was just going to start erupting, right then, without a hot period."

Then water was seen rising in Mastiff--normally.  Once again the Southwest Vents preceded feather by about 30 seconds, and the hot period started at 1533.  The duration was just 58s, and Mastiff did not overflow.  Starting after this hot period, the depth charging in Mastiff was so strong that the back vent was throwing a sizeable amount of water over its front rim.  Bijou continued its powerful play.

After the hot period, Grotto Fountain had a strong boiling episode, and this one finally led to an eruption at 1547.  The eruption was relatively weak, reaching only 20 feet, and lasted only 5 minutes.  At 1548, Grotto started normally.

The next hot period was at 1633, with the Southwest Vents starting about 30 seconds before Feather.  This hot period included Feather Satellite, but the duration was 4m33s and Mastiff did not boil appreciably.  After this, most gazers headed to Grand.  Since it was now very clear that there would be hot periods hourly with each Bijou pause, I decided that I needed to go in and get some food and supplies.  It looked like there was a storm moving in, and I did not want to miss the next big hot period.  As I unlocked my bike at Grotto, I commented to K.C. that Giant needed to figure out how to not have a hot period every time Bijou paused.  He asked me when I thought the "big" hot period might be.  I said I'd like for it to wait a bit longer--maybe 1930 or so.

While I was away, there was a call that Grotto was off by 1704, for a duration of approximately 75 minutes.  Then at 1714, Oblong erupted.  Right on time, Bijou paused again and the Southwest Vents started at 1736.37.  Feather was on at 1737.20 for a hot period lasting 1m36s.  There was only a dribble of overflow from Mastiff.

Around the same time, Mary Beth called that there was a delay at Grand.  Some gazers headed in for dinner while others stayed at Grand.  At Giant, Andrew Bunning, Dave Goldberg, and Thomas and Kevin Barger were busy playing various card games while Kitt Barger, Nellie Daugherty, Donna Friz, Julie Thomson, and I patiently waited for the next pause.  At 1833 water was seen in Mastiff--just barely visible to those standing on the lower rung of the railing.  It bobbed up and down several times, and then sank again for a footbath.  In the cage, we cheered.  Sort of strange to be cheering because, in fact, NOTHING had happened.  But it was the sign I had been waiting for.  I announced on the radio that this was the first Bijou pause since 0935 that had not resulted in a Giant hot period.

Then, at 1901 Bijou paused again.  After this pause, Bijou came on more weakly, and there was less activity in Mastiff--in fact, it had almost stopped having visible splashes.  Following this there was another pause at 1913, and this time we could see water purposefully rising in Mastiff….

...To be continued in Part 3, which is going to have to wait just a bit longer.


Here's a quick run-down of the events at Giant/Grotto on July 3, since there were so many of them….

0737 Giant hot period, d=8m15s.
0814 Oblong
0934 Bathtub
1029ie Giant hot period, d>3m.
~1135 Giant hot period, d=?
1238ie Giant hot period, d>1m.
1338 Oblong
1339 Giant hot period, d=2m10s.
1441 Giant hot period, d=4m33s.
1533 Giant hot period, d=58s.
1547 Grotto Fountain, d=5m.
1548 Grotto, d~1h15m.
1633 Giant hot period, d=4m33s.
1714 Oblong
1737 Giant hot period, d=1m36s.
1833 Footbath
1901 Bijou pause
1913 Bijou pause
1916 Giant hot period
1925 GIANT (d=104)
1953 Grotto Fountain
1958 Grotto
2200ie Oblong

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