[Geysers] Fan and Mortar details, 6/1/10

[Tara Cross]

This is a report on the June 1, 2010 eruption of Fan and Mortar.

The marker at Fan & Mortar was washed on May 26 for an interval of about 4 days, so the next F&M sit started on May 30.  F&M were watched during daylight hours on the 30th and 31st.  On the 30th there were two event cycles with exceptionally long pauses.  The first was a Gold pause lasting 63 minutes with lots of Main Vent splashing and Bottom Vent eruptions.  About 8 hours later there was a River pause lasting 52 minutes, again with lots of Main Vent splashing and Bottom Vent eruptions.

No events were seen on the 31st until the evening, when there was a double pause cycle with Gold and River pauses of more reasonable length (16 and 25 minutes, respectively) with Main Vent splashing.  Bottom Vent waited a while to join in, but erupted for about 15 minutes during the River pause.  The water levels in the minor vents looked better than the previous day, and there was actually some Upper Mortar surging starting 18 minutes after River.  The surges got up to the top of the cone, but did not progress further than that.  Meanwhile the water levels dropped in the minor vents.

We found the marker in place on June 1 so the wait continued.  I noticed a difference in the minor activity--on the 30th and 31st, Angle had been mostly quiet when River was off.  On the 1st, it was splashing between cycles a lot more.  Cycles were about 20-40 minutes during the morning.

At 1139, River shut off after a normal cycle.  It turned back on again along with Gold and Angle at 1149.  At 1158, River was off again and everything was very quiet.  We had just noticed this when Main Vent had its first splash at 1159.  This was followed by more splashing over the next 27 minutes.  At 1218, River turned on, and Main Vent continued to splash.  We thought we might get a River pause, but at 1226 the Main Vent splashing stopped.  I'm generally not encouraged when Main Vent and Gold are arguing over who will be in charge.  But Main Vent continued to roar while Gold was steaming, and the start of Gold was delayed until 1232, 14 minutes after River.  Angle splashed at 1233 and came on strong at 1235.

Water levels looked pretty good for a few minutes, but then they seemed to wane.  At about 1240 Gold looked like it was going into steam and I thought the minor vents had given up, so we got distracted by the start of Riverside.  But when I looked over my shoulder, I saw High and Gold steadily splashing to about a foot.  The splashing went up and down for the next 8 minutes, but High never stopped overflowing during that time.  Finally at 1248 High and Gold began erupting steadily to 5 feet and I called a lock.  High's activity got progressively stronger until it was practically in major eruption to at least 15 feet while Angle went into steam phase.  There were a couple of splashes in Main Vent before one of them triggered East Vent and the eruption started at 1254.

Fan & Mortar were kind enough to erupt during one of the few windows of sunshine we had the entire week.  The wind was blowing strongly towards the trail, which got completely soaked along with a lot of the observers.

--Tara Cross
fanandmortar at hotmail.com
 		 	   		  
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