
Activity Recorded by Data Logger  by Ralph Taylor 



Introduction 
Lion Geyser has been monitored electronically since 1998. Data from 1998 to mid2002 covers only the summer months, generally from late June to early October, but since the mid2002 we have attempted to monitor Lion all year. There are five large gaps in the record, 30 Dec 2002 to 2 Feb 2003, 21 Feb 2003 to 22 June 2003, 17 Nov to 16 Dec 1003, 7 Apr 2005 to 2 Jul 2005, and 23 to 29 June 2011. These gaps were the result of either logger failure or our inability to download the data resulting in the logger memory filling.
In 2008 a short gap from 1849 on 24 May to 0955 on 27 May resulted from the logger memory filling. The Lion logger failed once again after the November 2008 download, and was replaced on 20 March 2009. The data is continuous for the remainder of 2009 and 2010.
The 2011 data is interrupted by a gap from 23 to 29 June.
Lion Geyser is difficult to monitor. The stream from the eruption is thrown clear of the formation for the most part, and the sensor picks up primarily the big surge of water that initiates the eruption. This surge of hot water also has destroyed several loggers despite our best efforts to protect the devices. In the wintertime ice often diverts water from the sensor and causes some eruptions to leave no indication on the temperature trace.
Lion erupts in series. The initial eruption typically lasts six to eight minutes, and is followed by a series of zero or more inseries eruptions, typically two to four minutes in length. A series typically ends in a series of weak 'roars' that may or may not produce a small amount of splashing. After a series ends, Lion is quiet for several hours.
A complicating factor is the occurrence of minor eruptions within a series. For Lion Geyser, a minor eruption is a short duration (usually less than one minute) eruption that is usually followed in ten to twenty minutes by a fulllength eruption. A second complication that makes automatic detection of eruptions from the temperature trace more challenging is the occasional large preplay splash that produces a temperature signature almost like an initial eruption. These large preplay surges can delay an initial eruption by over an hour.
My analysis program does not distinguish between minor and major eruptions when producing the series length. The eruption files available here give the eruption number in the series as well as the time and interval. For the initial eruption (labeled 'Series Start' in the data files) the interval is the series interval, that is, the time since the start of the initial eruption of the previous series. For subsequent minor and major eruptions within a series (labeled 'Eruption #2' et. seq. in the file) the interval is the time since the previous eruption. Inseries intervals of under an hour generally indicate that the preceding eruption was a minor eruption.
In October 2009 Lion Geyser began having very long series, with as many as 20 eruptions in a series. Corresponding series intervals were around two days. The long series continued for the remainder of 2009 and all of 2010, with gradually decreasing series lengths and series intervals. In 2011 the series continue to be longer than pre2009 series, but the average and maximum length of the series is declining.



Activity in 2011 
The overall statistics for 2011 are shown at Lion Geyser 2011 Statistics.




The series interval graph shows all of the series intervals to date for 2011. The graphs for the current year are updated about every six weeks from October to June and weekly from June to the end of September. The yellow triangles show the eruption start times for Little Squirt Geyser. The Little Squirt eruption times are used as a surrogate for the socalled SMax (South [Geyser Hill] water level MAXimum), which is thought to represent a cyclic change in the hydrothermal energy on Geyser Hill. This hypothesis is described in an article in GOSA Transactions Volume IV titled Cyclic Hot Spring Activity on Geyser Hill, Upper Geyser Basin, Yellowstone National Park—Graphical and Interpretive Descriptions of the Geyser Hill Wave, Diurnal Effects, Seasonal Disturbances, Random (Chaotic?) Events, and Earthquakes by T. Scott Bryan. The orange diamonds show the first eruption of each recorded Dome Geyser series. Activity in Dome geyser is also known to affect some other features on Geyser Hill.

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The next graph shows the series intervals for the past few months at an expanded time scale.

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The next graph shows the series intervals for the past month.

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The next graph is a histogram of the distribution of series intervals. Note that in this and the other histograms displayed here the labels shown on the Xaxis represent the upper boundary of the class, not the midpoint. Geyser times are traditionally truncated. The graph at the right has class widths of 4 hours. The bar appearing above the label "24:00," for example, contains intervals from 20h01m through 24h00m. The shape of the distribution is generally that of a normal distribution.

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The final series interval graph is the monthly maximum, mean, median, and minimum series intervals.

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The next three graphs show the number of eruptions in a series, the first for the calendar year, the second for the most recent months, and the last as a histogram of the series length.

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Activity since 1998 
Lion's activity was been monitored only in the summer months from 1998 to 2002, so the full cycle is not shown on the graphs. The first graph shows all of the intervals recorded since 1998.

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The series intervals have been slightly longer since 2003 than was the case in 19982002. This can be seen a bit more clearly in the moving 1day median graph. Since the last quarter of 2005 the weekly median intervals rose until the last quarter of 2006, then dipped toward the end of the year before rising sharply in 2007 and 2008.
In October of 2009 Lion began having very long series of eruptions, with 20 or more eruptions in some series. The series intervals increased to two to three days since the series were so long. This graph along with the previous graph show the jump in series intervals clearly, and also show a slow decrease in series intervals since the jump. The shape of the decrease appears exponential, suggesting that whatever the nature of the change the system is relaxing to the previous state.

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The final graph shows the monthly minimum, mean, median, and maximum series intervals for all of the data available. This gives another view of the changes over the past decade. Both the average (mean and median) series interval and the maximum series interval are increasing slowly over the years and that the range (shortest to longest interval in a given month) is gradually increasing. The minimum series interval has remained consistent for the whole time covered by the electronic monitoring began.

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The graph to the right shows the number of eruptions (including minor eruptions) per series for the past several years. The October 2009 increase in series length shows very clearly in this view.

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Activity in 2010

Activity in 2009

Activity in 2008

Activity in 2007

Activity in 2006

Activity in 2005
