
Activity Recorded by Data Logger  by Ralph Taylor 



Introduction 
Great Fountain Geyser has been monitored using electronic data loggers since 1999. The record is not complete for these years but there is a substantially complete record from 1999 to date with few large gaps during winter months when critters damaged the loggers or we were not able to access the loggers because of bear management closures. The first gap is from 5 March to 15 June 2000, the next from 2 to 23 January 2004, then from 31 March to 31 May 2004, then from 7 November 2004 to 13 July 2005. There were a few short breaks of a day or two also.
The sensor for Great Fountain is located in one of the runoff channels about 50 meters from the vent, so the electronically recorded start times are two to four minutes later than visually obtained times. For statistical purposes this does not matter since the time between eruptions is not affected. The sensor easily detects the temperature rise signifying the wave of hot water resulting from the eruption start, but the individual bursts and the eruption duration are not distinguishable on the electronic record.
Electronic times are recorded to the nearest minute during the summer season (that is, while I am resident at Old Faithful, usually from midJune to late September). During the winter sampling times have varied from two to three minutes. Starting in the winter of 20056 and also for the winter of 20067 we used two loggers and sampled at three minute intervals. For some of the earlier summer season deployments sample intervals 30 seconds were used.
A new type of logger capable of recording temperatures every minute for several months was deployed in late September 2008 with a sample rate of 1m06s and that rate is being continued for the summer of 2009, and thereafter. In the spring of 2011 there is a gap of a few weeks because of my late arrival in Yellowstone.



Activity in 2011 
The statistical summary for 2011 is available at Great Fountain Geyser 2011 Statistics. A pdf of the same information is available at Great Fountain Geyser 2011 pdf




The activity of Great Fountain Geyser for 2011 to date is shown in the graph at the right. The graph is updated weekly during the summer months. The blue line shows all of the eruption intervals and the yellow line shows the 1week moving median interval.

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The Great Fountain activity for the three months prior to the last data download is shown in the next graph.

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The activity for the month prior to the last download is shown in the third graph at the right. The current year graph shows longer term trends while the other two shorter timeline graphs give a better sense of the most recent activity.

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Another useful representation of a geyser's activity is the distribution of intervals. The next chart shows the distribution of intervals for 2010 to date (blue), the most recent month of data (magenta), and the most recent week of data (yellow). This chart illustrates the range of intervals that necessitates the four hour prediction window. 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 30 minutes. The bar appearing above the label "8:30," for example, contains intervals from 8h01m through 8h30m.

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The next graph shows the Great Fountain Geyser interval statistics by month. This graph shows the maximum, mean, median, and minimum intervals for each month for which data is available. This chart summarizes the range and gives another perspective on the activity. The minimum value is an indication of how soon after the previous eruption one must arrive at Great Fountain to be (relatively) sure to see the next eruption and the difference between the minimum and maximum suggests how long the wait could be.

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The prediction results graph shows how the current prediction would have fared if applied over the past week and month. This graph shows the percent of all intervals that fall below the prediction window, in each quarter of the window, and the percentage of intervals that are longer than the window.
Please note that the prediction used to construct this graph uses only the time of the eruption and a standard prediction time. Actual predictions posted at the Visitor Center and at Great Fountain Geyser for much of the summer are adjusted based on observation of the duration of the eruption and the start of overflow, if known, and may be more accurate than this graph indicates.

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Activity since 1999 
One way to present the eruption interval data is to graph the interval as a function of time. The graph shown at the right shows all of the electronically recorded intervals since 1999.

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The graph of all intervals shows a wide variation. A better idea of trends in intervals can sometimes be seen by plotting a moving median value. The graph at the right shows the oneweek moving median intervals for all the data since 1999.

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The final graph, shown at the right, gives Great Fountain's interval statistics on a month by month basis, including the maximum, minimum, mean, and median intervals for each month. The very short (~4 hour) minimum intervals indicate periods of "wild phase" activity, during which Great Fountain has continuous low intensity activity for many hours. The short intervals occurred before and after the wild phase activity.

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Activity in 2010

Activity in 2009

Activity in 2008

Activity in 2007

Activity in 2006
