[Geysers] Giant Hot Periods and Eruption Sept 16th

Graham Meech meechg at erols.com
Wed Sep 21 17:21:17 PDT 2005

I finally made it home after my flight was canceled from Jackson to Salt
Lake, about 24 hours from Old Faithful to my home in Virginia.  But of
course with Giant having erupted I didn't care about it too much!


Giant was watched fairly closely over its last interval and I got to see
many of the hot periods as well as worrying about missing a strong hot
period overnight so I didn't get much sleep some nights.  The main thing of
note the day before Giant erupted was that it had 3 strong hot periods and
all were over 9 minutes long and Mastiff was surging 4'.  Mastiff also depth
charged for 1.5 hours after one strong hot period.  Earlier in my two week
trip it was having shorter hot periods and not as much surging.


Some definitions:  

Weak hot period = less than 5 minutes, no overflow or minor overflow from
Mastiff that didn't wet India much if at all

Strong hot period = 7 or more minutes long with India 70% covered or more

GHP = Giant hot period

FS = Feather Satellite

MOF = Mastiff overflow


Most hot periods fell into the weak or strong categories with the exception
of a couple that were late in Grotto Marathons and one earlier on the day it
erupted.  Strong hot periods were mainly 5-7 hours apart but some were from
3h45m to 8 hours apart (excluding Marathon activity).  Here is the data from
my notes, the OF logbook and key information from Dave Leeking and Suzanne
Getter close to the eruption.  You can skip down to the bottom for the
eruption hot period if you don't want all the details.  There were patterns
in the hot periods, Sept 13th and 15th had similar sequences and intervals
(strong, weak, weak, strong, SW vent bathtub).


August 29

1100 Giant


Aug 31

0816 Grotto

0847ie GHP d >2.5m

1405ns Grotto

1708 GHP d=3m55s 

1821 Grotto


Sept 1

0911 GHP d~1m25s

1055ie GHP d>= 4m

1119 Grotto still ie 1546 (marathon?)


Sept 2

1203ie GHP d >=7m

1531 GHP d~2m43s


Sept 3

0723 GHP d<2m

0848 GHP d~7m

~1043 GHP

1108 Grotto

1222 GHP d>5m

1400 GHP d~4m26s

1527 GHP d=1m31s

1646 Grotto

1704 GHP d=8m53s


Sept 4

0433ie Grotto marathon


Sept 5

0806 GHP d=3m45s, FS, MOF

~1044 GHP d~2m

1309 GHP d=3m19s, FS

1434 Grotto (first post marathon)

~1443 GHP

1626 GHP d=7m45s, FS, MOF bit not very strong, Mastiff 2', India mostly
covered, Cave 2"

1942 GHP d=3m15s, FS, MOF but not much


Sept 6

Before 0440 GHP, weak, India dry but water running off platform

0611 GHP d~9m FS, MOF heavy, India covered

0830 Grotto (3rd?)

1426 GHP d=2m

1524 Grotto (4th?)

1658 GHP d=7m43s FS, MOF, Mastiff 3', Cave 1'

1708 Feather restart d=4m3s, big vertical surges in Giant

1928 GHP d=2

2144 Grotto (6th?)

2232 GHP d~8.5m, FS, MOF, heavy overflow


Sept 7th

0433ie Grotto (7th?)

0536 GHP d~7m45s, FS (started 6m after Feather), MOF

0859 Bathtub

0929 Grotto Marathon

1014 GHP d=3m5s FS, very little MOF

1129 GHP d=8m15s, FS, MOF, Mastiff 2'

1654 GHP d~6m30s, slight MOF but no FS - unusually long for such a weak GHP
but it was 7h25m into the Grotto marathon


Sept 8th

~0645Grotto Marathon ends 

1108 GHP d=9m25s, FS, MOF Mastiff 3', Cave and Turtle bubbling, India 90%
wet (1st post marathon hot period)

1120 Feather restart, d1m10s, a couple of vertical surges from Giant

1522 GHP d=3m50s, FS, India 50% wet

1726 Water in Mastiff but no bathtub afterplay

1820 GHP d~8m50s, FS, MOF Mastiff 3', turtle splashing


Sept 9th

~0600 GHP weak

0822 GHP d=1m45s slight MOF

O844 Grotto (3rd?)

1010 GHP d=8m20s, Mastiff 2', Cave 2'

1019 Feather restart, d=5m

1325 Grotto (4th?)

1447 GHP d=7m40s, FS, MOF (not very strong), Cave pulsing 0-3', Giant showed
water a lot during the hot period and surged a lot in afterplay

1738 Southwest vents on but nothing else d=2m

~1844 Southwest vents on but nothing else

1849ie Grotto Marathon?

1948 GHP d=7m40s


Sept 10

0450ie Grotto still in marathon

1502 GHP d=8m35s FS, MOF (1st post marathon)


Sept 11

0443ie Grotto

0600ie GHP d>7m FS, MOF, India flooded

0811 GHP D<2m FS

1032 GHP d=3m25s, FS

1150 Grotto

1215 GHP d-9m30s FS, MOF Mastiff 2'


Sept 12

0753 GHP d~9m SW, MOF India flooded

1233 GHP d=4m FS, MOF Mastiff 1-2', India 50% wet

1439 GHP d=2m35s FS

1622 GHP d=9m20s FS, MOF

1740 Grotto

2007 GHP d=8m, FS, MOF India covered but OF didn't seem that good.  Interval
of only 3h45m between strong hot periods!)


Sept 13

~0520 GHP weak India dry

0606 Grotto

0641 GHP d=2m10s

0925 GHP d=9m25s, FS, MOF Mastiff 1-2', cave 2", India flooded

0935 Feather restart, d=3m25s, nice vertical surging in Giant

1324 GHP d=3m

1447 GHP d=3m

1458 Grotto

1605 GHP d=8m40s FS, MOF Mastiff ~ 1.5', no Feather restart but some good
vertical surging in Giant and some right-to-left splashing, good depth
charging in Mastiff that went on for a long time

1949 Southwest vents on but nothing else d=4m30s

2120 Grotto Marathon starts

2131 GHP d~2m, FS


Sept 14

0100 GHP strong, India covered, strong surging in afterplay, Marathon
recovery hot period

0621ie GHP d>4m FS, MOF, India 50% wet

~2019 Grotto marathon ends


Sept 15

0232 GHP d=10m, India covered

0750 GHP d=4m25s, FS, MOF, India ~ 70% wet

0948 GHP d=3m40s, FS, MOF but not much

1149 GHP d=9m30s, FS, MOF mastiff to 2' and later 2-4', Turtle~6", Cave
boiled, India covered

1156 Grotto (1st)

1520 GHP d=2m

1639 GHP d=1m50s

1723 Grotto (2nd) d>4h (I thought this was going to be a marathon but it was

1808 GHP d=9m5s, FS, MOF mastiff ~3-4', good boiling and surging in Giant
during the hot period, India wet

1820 Feather restart d=2m20s, 1.5 hours of depth charging in Mastiff that
ended with a bathtub

2039 Southwest vents on but nothing else d~1m


Sept 16

Before 0550 GHP - India damp

Grotto 0605, off before 0915

0632 GHP d=6m30s, FS, MOF but not much, India dry, feather strong to the top
of Giants cone but overall a weak but long hot period

0805 GHP d<3.5m, FS, little MOF


..and then.

~0941 Bijou Pause

0943 Water visible in Mastiff (me standing on the lower rail, I don't have
the balance for top rail)

Water rose very slowly, stopped and looked like it would drop, then came up
slowly again.

0949 GHP started, Feather and SW vents on, but this was very slow, 6 minutes
after I saw water rising in Mastiff!  Mastiff starts to overflow 20 seconds

0950 FS on

0953 up to this point Mastiff had been doing some good boils but the wind
was blowing steam in front of it.  Mastiff then started to surge ~4' and
Julie Thompson at Oblong could see it as large wide surging and started to
scream with each surge

0954 things moved fast - I could see Mastiff surges to the top of the cone
now, lots of noise and overflow but it was not staying up all the time

0954 Mastiff erupts continuously - late this minute..Mastiff surges over the
tree line seen from the railing in the cage. I call that an eruption, not
just surging.

Then the noise and water flowing off the platform was amazing with Giant
spilling water out the front.

0956 GIANT - we backed off the platform just before Giant washed it clean
(and drowned my pack).  Only 7 minutes into the hot period!

Catfish started at some point but I didn't notice when.  Very big noisy
eruption.  Lots of happy gazers!


The duration was 105m.


I noticed that Bijou was back in eruption on Sept 17 at 1800, so the
recovery is on!




Graham Meech.








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