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Geysers of the World   

Geysers of Yellowstone   



  Castle Geyser
Feature Type: Geyser
Geyser/Spring Type: Cone geyser

Upper Geyser Basin
Grand and Castle Group

Castle is a cone-type geyser and has the largest cone in Yellowstone. Eruption height is 60-90 feet. The usual major-to-major interval in 2010 is around 14 hours with extremes of 11-1/4 to 19-1/2. A normal eruption consists of a 20 minute water phase that is followed by a 40 minute steam phase. The first 15 minutes of the steam phase is relatively forceful and fairly loud. For many this is the most enjoyable part but requires one to be close by in order to hear it best. As in most geysers that have a steam phase, the change from water to steam is gradual and an exact time for the change can rarely be noted.

Castle often has minor eruptions which last only a few minutes. Any eruption that stops prior to the steam phase is considered a minor eruption. When Castle has a minor eruption, it becomes unpredictable until it has its next major eruption.

Castle is probably a very old spring. Estimates put the age of its 12 feet high cone at 5,000 to 15,000 years. It would take that long for the sinter to build up so high. Even more remarkable is that Castle's cone sits on top of an even more massive sinter formation deposited by an earlier spring.

What to look for:
Many eruptions of Castle start with almost no warning. During the period between eruptions, Castle will often splash but this usually does not appear to indicate anything. The easiest way to determine if Castle is due to erupt is by using the current average interval and the time of the previous eruption.

The one time that splashing does indicate something is when it is what is called "sloppy play". This occurs after a minor eruption. Sloppy play is characterized by frequent splashes and jetting and usually starts soon after the minor eruption and continues until the next major eruption.

Major and minor eruptions start the same but a minor stops without warning after a few minutes of play.

Electronic Monitor Files
Castle eruptions for 1997.TXTCastle eruptions for 1998.TXT
Castle eruptions for 1999.TXTCastle eruptions for 2000.TXT
Castle eruptions for 2001.TXTCastle eruptions for 2002.TXT
Castle eruptions for 2003.TXTCastle eruptions for 2004.TXT
Castle eruptions for 2005.TXTCastle eruptions for 2006.TXT
Castle eruptions for 2007.txtCastle eruptions for 2008.txt
Castle eruptions for 2009.txtCastle eruptions for 2010.txt
Castle eruptions for 2011.txt 

Some of the temperature data used to derive the eruption times and durations used in this section were collected by Ralph Taylor under a National Park Service research permit, and the remainder was collected by personnel working for the Geology Department of the Yellowstone Center for Resources (including Ralph Taylor). The loggers are a combination of loggers owned by the NPS and Ralph Taylor. Analysis of the raw temperature data to extract the eruption data was performed by Ralph Taylor. The eruption time files on this website may be used provided that Yellowstone National Park is credited for the temperature data and Ralph Taylor is credited for the eruption times.

Activity in 2011
Activity Recorded by Data Logger - by Ralph Taylor  

Castle Geyser has been monitored electronically since 1997. Data from 1997 to late 2002 is intermittent, but since that time the record is nearly complete. Our original location for the data logger was subject to damage from ice and water, and two gaps in 2004 were caused by failed loggers. We have since relocated the logger to a safer location and are having better success with continuous recording.

A gap in data from 2019 on 24 May 2008 to 1035 on 27 May resulted from the logger's memory filling.

Activity in 2010  
Since Castle has two distinct sorts of eruptions the analysis is more complex than for other geysers. The statistical summary for 2010 shows the activity analysis. A pdf of this summary is at Castle Geyser Recent Activity Summary. The "all eruptions" box shows combined interval statistics for both major and minor eruptions. The boxes on the right break the intervals down into three categories: Major to major intervals, minor to major intervals, and the first major-to-major interval following a minor. The latter category is significant since we note that the first full major interval following a minor eruption is fully an hour longer than the successive major-to-major intervals. This factor greatly improves the prediction accuracy.

The overall interval graph shows all of the intervals for 2010.
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The next graph shows the intervals for the past few months at an expanded time scale. In recent years the minor intervals have tended to be clustered; that is, for a few days there are frequent minor intervals, but there are also periods of a week or more with no minor intervals.
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The next graph shows just the major-to-major intervals, excluding the minor-to-major intervals. The black points indicate major-to-major intervals and the red points show the first major-to-major interval after a minor. Nearly all of the intervals fall in a narrow band between 13 and 14 hours, with a few much longer intervals exceeding 14h. The black points that indicate very long intervals, especially those in the winter months, may represent intervals with an undetected minor eruption.
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The overall interval distribution shows a skewed distribution for the major-to-major intervals with the minor-to-major intervals represented by the bar at the left and the long intervals represented by the short bars to the far right. Note that in this and the other histograms displayed here the labels shown on the X-axis 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 "13:30," for example, contains intervals from 13h01m through 13h30m.
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The predictions for Castle are usually quite good providing the overnight activity (minor or major eruption) is known. The final graph is a prediction results graph, showing where the eruptions fell within the prediction window, which is plus or minus one hour for Castle. Most of the time, Castle's predictions are well above the 90% target.
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Activity since 1997  
A plot of Castle's intervals shows that major eruptions are more common than minor eruptions, typically comprising more than 75% of all of the eruptions. The plot of all of Castle's intervals shows the major eruptions as the heavy band between 11 and 13 hours and the minor eruptions as the shorter intervals, dropping to under 3 hours in some cases. When Castle has a minor eruption the interval until the next major eruption is not predictable.

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However, when Castle has successive major eruptions, the intervals are quite a lot more consistent, as shown in the second graph.

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The multi-year trend is to increasing intervals, from 11 hours between major intervals in 1997 to nearly 14 hours in 2011. There was a sharp increase in Castle's intervals coincident with the large earthquake at Denali in Alaska in November 2002 resulting in average intervals 35 minutes longer after the quake than before the quake.
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Activity in 2009
Activity in 2008
Activity in 2007
Activity in 2006
Activity in 2005

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A vintage picture of people climbing on Castle Geyser by Haynes. Park visitors are no longer allowed so close to this geyser. In fact, this is a destructive and dangerous practice that is now illegal.

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This is a view of the Castle Geyser's cone. Sinter, the material the cone is made from, deposits very slowly in the Upper Geyser Basin. Because of this, the cone is estimated to be over 5,000 years old. The sinter formation on which the cone sits was deposited by a hot spring that preceded the geyser. This underlying sinter formation has been estimated to be as much as 200,000 years old.

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Please note - this site is currently under constuction. Please visit for more information.  Last update 01-29-2017

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