[Geysers] Geyser Report: Fan & Mortar details, 7/29

[Tara Cross]

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

As promised, I am posting the details of the pre-eruptive activity for the 
July 29 eruption of Fan and Mortar.

Fan & Mortar were observed for approximately 24 hours before the eruption.  
During that time, observers saw mostly garbage cycles with a lot of 
continuous splashing from Angle.  There were several lame event cycles, 
which included at maximum 20 minutes of splashing in Main Vent and up to one 
River Vent pause.

Paul Strasser observed some odd behavior around 2000 on the 28th.  The minor 
vents shut off after a normal cycle, and Angle Vent continued to splash 
after River was off.  Then, Main Vent had a single splash.  The vents were 
then off for about 30 minutes before starting a normal cycle.  One cycle 
later, there was an event cycle including one River Vent pause and Main Vent 
splashing, starting around 2130.

After this there were two more weak event cycles:  About 10 minutes of Main 
Vent splashing during a normal River Vent off period just after midnight and 
20 minutes of Main Vent splashing along with a 3-minute River Vent pause 
around 0200.  After this event cycle Kitt took over duties at F&M and saw 
normal cycles with occasional splashing from Angle for over 3 hours.

After this events took place as follows:

0538 Everything shuts off, including Angle
0540 Main Vent begins to roar
1546 Main Vent begins to splash, starting slow and then building to more 
consistent splashing
0604 River Vent on
0611 River Vent off (River pause)
0617 River Vent on
0626 River Vent off (River pause; double pause)
0636 Main Vent has a huge splash, after minutes of near-constant splashing
0637 River Vent on
0644 River Vent off (River pause; triple pause)
0650 River Vent on
0658 River Vent off (River pause; QUADRUPLE pause)
0703 River Vent on
0708 Angle on, then Gold on about 10 seconds later
0718 High Vent builds into lock
0727 FAN AND MORTAR

The water levels were excellent as soon as Gold started.  We were pretty 
skeptical after the quadruple pause (which, by the way, was the first I had 
ever seen; I know Scott reported one earlier), but the water levels just 
continued to look great until High Vent rather quickly built into a lock.  
After a few minutes, Gold Vent joined in the lock and Angle went into steam 
phase.  There were at least two splashes in Main Vent during the lock, and 
then it had some very large splashes/surges immediately prior to the start 
of the eruption.  Then East Vent bursted up and Main Vent pooled before 
rising up along with Upper and Lower Mortar.

The eruption was Fan-dominated; Mortar was quiet for the first 2 minutes of 
the eruption.  Main Vent had several surges that sent water past the bumper 
log at Backwater Spring, even though the wind was blowing primarily away 
from the trail.  The viewing was quite good in terms of wind direction but 
the lighting was poor due to cloud cover.  The clouds did bring us a 
gorgeous double rainbow as the sun rose during the event cycle, however.

Since I have been watching Fan & Mortar, I only know of one other reported 
quadruple pause--one reported earlier this year by T. Scott Bryan.  However 
this event cycle was very strong from the beginning and Main Vent splashing 
persisted throughout until River Vent started the final time.  After giving 
us less than 10 minutes for the previous eruption, we got 101 minutes.  Go 
figure.

Just to summarize, pauses lasetd 6, 11, 6, and 5 minutes; Main Vent 
splashing started 101 minutes before the start of the eruption; lock lasted 
9 minutes; and the eruption began 24 minutes after the start of River.

--Tara Cross
fanandmortar at hotmail.com