[Geysers] Fan & Mortar details, 8/26 and 9/3

[Tara Cross]

I was fortunate enough to see both eruptions of Fan & Mortar that occurred during my visit to the park.  I'll first share the details of the eruption event cycles, and then share a few other observations that I made while I was there.
 
First of all, a big thank you to Dean Lohrenz and Graham Meech, who not only called the eruption cycles but also many other event cycles, and to the various others who covered Fan & Mortar, especially Cynthia Barwin.
 
August 26 (details from Dean Lohrenz)
 
1956 River on
1956 Main Vent splash
2001 River off (River pause)
2009 River on
2018 River off (River pause)
2027 Bottom Vent, d~10m
2038 Bottom Vent, d~1m
2041 River on
2041 Bottom Vent, d~1m
2042 Gold
2044 Angle
2052 High & Gold vents in lock
2056 FAN & MORTAR
 
When the minor vents came on, the water levels stayed very high and never waned.  High Vent built into lock and was erupting to about 6 feet, then quickly Gold joined in and High was erupting to 10-12 feet for most of the 4 minutes that it was in lock.  Interestingly, there wasn't much steam coming out of Main Vent or East Vent; the eruption started very suddenly with East Vent, followed about 10 seconds later by the rest of the vents.
 
The conditions weren't terribly good for the eruption, as it occurred while the sky was mostly dark between sunset and when the moonlight started to take effect.  However I did think to bring a flashlight with me, so we were able to see that it was a powerful eruption, dominated by Mortar.  We finally got some moonlight on the bursts at the tail end of the eruption.
 
 
September 3 (details from Graham Meech)
 
After a series of short, weak cycles and "coughs," Bottom Vent started to splash and events progressed as follows:
 
1153 River & Gold on
1158 River & Gold off (Gold pause)
1217 River on
1221 River off (River pause)
1232 Main Vent large splash
1233 Bottom Vent, erupted for about 12 minutes with brief pauses
1247 River on
1249 Gold
1252 Angle
1302 High Vent in lock
1304 Gold Vent in lock
1308 FAN & MORTAR
 
Once again, the minor vents stayed very strong until at about 1302 High Vent built into lock for the first time.  Gold joined in at 1304.  However, the behavior this time was a major contrast from the previous eruption because High & Gold went in and out of lock 3 times.  Words cannot possibly do justice to the roller coaster that we experienced with each rise and drop.  As Scott reported earlier, the vents literally went from full lock to 10 feet, down to almost nothing (no water in Gold and just a dribble from High), then came back up again.  Finally, even though there was heavy steam coming from Main Vent and East Vent, the minor vents dropped down to nothing for a third time, and I thought that there would be no eruption.  Then someone yelled that East Vent had splashed, and the eruption started.  East erupted by itself for about 8-10 seconds before the rest of the vents joined in.
 
Interestingly, both Upper and Lower Mortar surged up with a lot of water at the beginning of the eruption, but then they stopped erupting for several minutes.  When Mortar did come back, only Upper Mortar had water; the most I ever saw from Lower Mortar was wispy, steamy jetting about 6-7 minutes into the eruption.  Upper Mortar was also very steamy.  But the wind direction was such that the viewing was best for Fan anyway, as can be seen from the picture that Pat Snyder posted (and congratulations to Pat and the other gazers who were seeing their very first Fan & Mortar!).  It was a wonderful treat for the Labor Day crowd.
 
 
As for Fan & Mortar's behavior between eruptions, it appeared that event cycles were generally occurring every 3-12 hours; on most days, at least 2 event cycles were seen during daylight.  One difference I noticed between the behavior I observed during my recent trip and what I had seen earlier in the summer is that the pauses were getting longer.  The Gold pause on September 3 was the first of any length that I had heard of all year; as a matter of fact, I had not heard of any Gold pauses occurring prior to Labor Day weekend.  There were also several long pauses observed after the 9/3 eruption; Cynthia Barwin saw a River pause lasting 54 minutes on 9/7, and a Gold pause lasting 57 minutes on 9/8.  Event cycles continued to include strong splashing in Main Vent and Bottom Vent eruptions.  I also saw a few droplets in Upper Mortar several times during pauses.
 
It was just wonderful to have my favorite geysers back, and I hope that the intervals continue to stabilize and shorten throughout the fall and winter so that there will be many chances to see it in 2008.
 
--Tara Cross
fanandmortar at hotmail.com
 
 
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