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| Activity Recorded by Data Logger - by Ralph Taylor |
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| Introduction |
Riverside Geyser has been monitored electronically using data loggers since 2000. This geyser is a visitor favorite, with regular eruptions lasting 20 minutes or so and a beautiful setting. We have had mixed success in monitoring the activity, however. The sensor is located so that it picks up the water temperature in the pool that forms around the vent when overflow starts. This gives both overflow duration and eruption start information (the latter inferred by the drop in temperature caused by the cessation of overflow once the eruption starts). Since the geyser is a cone-type geyser with almost all of the eruption water landing in the Firehole River, the sensor is not able to record eruption durations.
Over-winter logging has been problematic because of the difficulty of access to the geyser with snow and ice, and because our original logger location was covered by a thick layer of ice. Another nagging problem has been the displacement of the sensor from the pool which makes the temperature trace difficult or impossible to interpret. The result of all of the difficulties is a fragmentary record, which was still the case in 2006. In the winter of 2006-7 we were successful in obtaining over winter data at last. In 2007-8 we were unable to download the data for one six-week interval due to heavy snow cover. Over the winter of 2009-2010 we were successful with the exception of November, when a logger problem resulted in a month-long gap in data.
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| Activity in 2010 |
The overall statistics for 2010 are shown at Riverside Geyser 2010 Statistics. This summary gives the statistics for all intervals, and separately for long and short intervals (the two modes) for the current year-to-date, the past month, and the past week. A pdf of this summary is available at Riverside Geyser Recent Activity Summary.
I have also included statistics on the duration of overflow and the time from the start of one eruption to the start of the subsequent overflow. The reason for these statistics is discussed later in this article.
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The interval graph shows all of the intervals for 2010. The blue line shows the interval data, and the green line shows the moving median interval. The range of intervals spans about 50 minutes for most of the year. This is, as we will see, the result of Riverside's switching between two different intervals. The yellow line represents the time between the start of each eruption and the start of the following overflow. The orange line is a plot of the overflow length.
Note that the overflow length (the orange curve) looks much like the interval plot. This is because almost all of Riverside's variation is in the length of the overflow portion of the cycle. Eruption durations are within a minute or so of 20 minutes. The quiet time is shown to be around 4h32m (see the statistics referenced above). The quiet time is very consistent with a standard deviation of just 3m37s for all of the data shown, and just 2m58s for the last month of data. The red lines are linear regression fits to the interval data, which I include to give a sense of the trend in eruption times.
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The next graph gives just the data for the past two to three months. The Y-axis scale is expanded to show the interval characteristics more clearly. It is more apparent that the intervals are either short (around 6h0m) or long (around 6h40m), with few intervals falling between these values. The quiet time, shown in brown at the bottom of the graph, is consistently between 4h20m and 4h40m.
The red dashed lines show the limits of the prediction window used by the NPS to predict the next eruption.
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The interval histogram illustrates the bimodal nature of Riverside's intervals quite nicely.
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The second interval histogram plots the same data in one minute buckets, which shows the bimodality more clearly.
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The companion plot of overflow length shows very nearly the same shape.
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With the regularity that Riverside exhibits, predicting the next eruption would seem simple. And it is, provided the time of the previous eruption is known. The graph at the right shows the prediction results assuming that each eruption start time been known. The predictions are made using an interval of 6h05m, which is midway between the two modal peaks of 5h48m and 6h26m. Since Riverside is bimodal, however, and the modes are typically 40 minutes apart, this means that the eruptions never happen at the predicted time, but are either "early" or "late" depending on whether the overflow is long or short!
Since the modes are only 40 minutes apart, this does not represent a big problem if the previous eruption time is known. Until the first eruption of the day is seen, however, predictions have to be made using double or triple intervals, which leads to much uncertainty, especially when Riverside is "stuck" in either long interval mode or short interval mode.
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| Activity since 2000 |
Riverside is known for its regularity. It is also known for being "bimodal"; that is, it has two different intervals at which it likes to erupt and switches between the two intervals. This effect is visible in the overall plot of interval vs time, shown at the right.
There has been some variation in the intervals, but they generally lie between 5h30m and 6h50m. Since July of 2003 there has been little change in Riverside's activity and intervals have remained largely between 5h50m and 6h50m.
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Activity in 2009
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Activity in 2008
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Activity in 2007
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Activity in 2006
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Activity in 2005
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