[Geysers] Fan and Mortar eruption details 7/31/10

[Suzanne Strasser]

Fan and Mortar erupted at 2330 on 7/31/10.  Below are the details of the
event cycle leading up to the eruption.
 
I arrived at Fan and Mortar at around 2130.  Paul had been on watch for the
past 3 hours and Fan and Mortar cycles had been in garbage mode, with Angle
Vent spurting between cycles.  When I arrived the vents were in the middle
of a normal cycle.  After the cycle ended my attention was diverted by an
approaching storm, but the weather passed to the north so I decided to stay
on watch a little longer.
 
I noticed the first huff in Main Vent at 2235.  It is possible it could have
started huffing a few minutes earlier since I had been watching the storm,
but my recollection is that the area was pretty quiet beforehand with only
the noise of the wind in the trees catching my attention.
 
I had two flashlights with me: one maglite and another small light that was
much dimmer but did not pick up as much steam.  Using both lights I
continued to see and hear Main Vent huff for the next 10 minutes but I was
never able to see any water splashing out of Main.  At that time Bottom Vent
was splashing periodically but not erupting.
 
At 2245 there was a shift in wind direction with the steam blowing directly
towards me: it was very difficult to see what was happening with the vents
but River Vent was obviously on and I could still hear Main Vent huffing.
 
Sometime before 2300 River Vent quit:  I don't have an exact time since I
was scrambling around to get out of the steam.  But by 2300 the wind had
shifted away from the benches and I was once again able to see the vents.
River Vent was obviously off, and at 2300 Main Vent gave a huge splash of
water that my maglite was finally able to illuminate.  Bottom Vent was also
in eruption at that time, and I estimate its duration was about 5 minutes.
 
River Vent came back on sometime between 2303 and 2305.  After that the
events were much easier to see, with the wind continuing to blow away from
the benches.  Below is the full set of event cycle times:
 
2235:  Main Vent roar
2245:  Main Vent continued to roar, River Vent in eruption
sometime before 2300:  River Vent quit.  RIVER PAUSE
2300:  Main Vent huge splash, Bottom Vent in eruption
sometime between 2303 and 2305:  River Vent on
2311:  Gold Vent on
2313:  Angle Vent on
2315:  water levels look excellent
2321:  lock
2329:  thick water surging in Main Vent
2330:  eruption, Main Vent start
2344:  first pause
2346:  eruption continues
0003:  last water
0005:  last steam huffs
 
The eruption was Mortar dominant.  Paul, Linda, and Kevin arrived before the
lock and supplied an additional maglite.  We had one maglite illuminate Fan
and the other on Mortar.  The moon was not yet up, so it was very dark, but
the wind continued to cooperate and the steam blew to the west.  We were
able to watch the entire eruption on the jugwalk without getting very wet.
Fan's first surge went over the jugwalk but not much farther beyond; the
area beyond the jugwalk stayed fairly dry.  Mortar's water was easier to see
than Fan's.  My impression of Fan was watching the very top of the water
column cascading down.  It was too steamy to see the base of Fan's vents for
the first part of the eruption.
 
Ten minutes into the eruption, the moon rose and aided us in watching the
end of the eruption.  Darren Rose arrived about 6 minutes into the eruption
and was still able to see good water out of Mortar.  Nobody else made it
down to see the eruption.  After the storm passed it was a very nice evening
and not too cold.
 
It was nice having closure to the end of our vacation.  We were able to
leave the Park on Sunday morning without worrying about missing Fan and
Mortar.  Here's hoping the next eruption is in daylight with lots of gazers
there!
 
Suzanne Strasser

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