GOSA (The Geyser Observation and Study Association) Grand Group   

Grand Group: - Map

[Grand Group introduction provided by Kyle Chumbley.]

The Grand Group is centered around the world’s largest predicted geyser, Grand Geyser. It includes ten significant geysers. Some of the more important members of the Grand Group are: Grand, Turban, Vent, Rift, and West Triplet.

Most of the Grand Group geysers are fairly frequent, and they all affect each other. Grand can only erupt near an eruption of Turban, Vent generally only erupts with Grand, Rift eruptions have delayed Grand in the past, and the Triplets can do the same. Grand has been unpredictable throughout much of the park’s history, but today is the world’s largest regular predicted geyser.

This group is connected to the Sawmill Group to the south and to Economic Geyser, more than 400 feet to the north. In the past Economic’s activity has rendered Grand dormant. Now, fortunately, Economic is rare, and Grand remains active. 


Grand Geyser: Click for more information.


Rift Geyser: [Picture] [Map]

Rift is a small but important geyser located in the trees south of Grand Geyser. It was first seen to erupt in 1924. While dormant some years, in recent years, it has been a relatively regular performer.

Rift is often preceded by an eruption of West Triplet Geyser.

Rift erupts in a number of jets along a fissure in the sinter. In the last few years, the central portion, around the largest vents, has subsided some so that Rift now erupts through a shallow pool. This pool is present only during the eruption.

Intervals for Rift range from less than 12 hours to more than two days. Durations often last more than two hours and can last up to four hours. Heights of the tallest jets rarely reach four feet.

Because of its long duration and steady flow of water, Rift puts out a large amount of water during an eruption. In fact, some years, eruptions of Rift have been known to delay an eruption of Grand Geyser by about two hours. No one knows why this affect only seems to occur some years and not all years but when it does occur, it is highly observable.

Rift erupts from what appears to be a long dead hot spring. On examination, it is easy to see the half buried sinter rim of an old hot spring that appears to encircle Rift.


Turban Geyser: [Map]

Turban Geyser is intimately connected to Grand Geyser. Grand Geyser only erupts near the start of an eruption of Turban.

During the hours prior to an eruption of Grand, Turban erupts every 15-25 minutes for about five minutes. During Grand's eruption, it will erupt continuously often increasing in size from its normal 5-10 feet to about 20 feet. For the hour or so after Grand's eruption Turban erupts intermittently with Vent Geyser.

Turban is located in the large sinter mound next to Grand's pool. Many people upon first seeing the mound assume that it is Grand instead of Turban. Turban is a fountain-type geyser.

See Grand Geyser for more information.


West Triplet Geyser: [Picture] [Map]

Because of its nearness to the boardwalk and the fact that it often plays just prior to or after an eruption of Grand, West Triplet is a fun and relatively easy geyser to watch. In the past, an eruption of West Triplet was a bad omen for Grand, often delaying Grand by two or more Turban cycles. Fortunately, his relationship has not been seen for years. Another relationship which doesn't seem to have changed in recent years is that West Triplet often precedes an eruption of Rift Geyser.

West Triplet is a fountain-type geyser, erupting through a funnel shaped pool. The maximum height is about 10 feet. Durations range from minutes to hours. Intervals range from hours to days.

What to look for:

Prior to an eruption, water slowly rises in West Triplet. The water level may drop some at about the time Turban erupts but will rebound. Eventually, the water over the vent begins to pulsate and low thumping noises may be heard. Sometimes the eruptions starts before overflow is reached other times it overflows before it erupts. At times, it can overflow for a long period and then drop without erupting.

The sound and pulsing are the most enjoyable part of the eruption.


Vent Geyser: [Picture] [Map]

Vent Geyser is intimately connected to Grand Geyser. It usually only erupts immediately after the start of a Grand eruption and intermittently for an hour or so afterwards. On rare occasions it can just precede Grand and on extremely rare occasions it has erupted by itself.

Vent is a cone-type geyser. Its maximum height is about 75 feet, which it reaches in the first few minutes of the eruption. It then quickly decreases to 20-40 feet. The maximum height is often obscured or completely lost in the steam and spray from the much larger eruption of Grand.

See Grand Geyser for more information.


Beauty Pool/Chromatic Pool: [Picture] [Map]

Chromatic Pool and, especially, Beauty Pool are two of the prettiest pools in the Upper Geyser Basin. The two pool's plumbing systems are connected underground. They undergo an exchange of function. One pool will overflow while the other stands below overflow then they will exchange and the first will stand below overflow while the second overflows. This exchange occurs relatively abruptly but only every few weeks to months. Usually, the pool that is overflowing has the most variation in colors due to the the temperature changes as the water flows out of the pool which allows differing types of cyano-bacteria to thrive.


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