GOSA (The Geyser Observation and Study Association)

Giant Group,   Daisy Group


Grotto Group 


[ Giant Group - Map ] [ Daisy Group - Map ]
Grotto Group - Map ]

The Giant Platform with Bijou Geyser erupting on the left, Mastiff Geyser steaming lightly in the center back and the large cone of Giant Geyser on the right.

Giant Group: - Map

The Giant group was often almost completely ignored during the long years from 1956 to 1996 that Giant Geyser was dormant or infrequent. The only major geyser to be seen in the group for most of this time was Oblong Geyser. In 1996 that started to change. All it took for many geyser gazers to get interested in the group was to either see an eruption of Giant Geyser or to know that an eruption of this superlative geyser was possible. In July 1996, Giant Geyser started one of its best periods of activity ever seen and its best activity since 1955. Between July 1996 and January 1998, the longest interval was two months. By the fall of 1997, intervals were between 3.5 and 5 days. As of this writing, the activity is still continuing.

Giant Geyser connects into all of the geyser of its group. It also connects to the Grotto Group and possibly to the Daisy Group.

Bijou Geyser: [Map]

Bijou Geyser erupts almost continuously. Because of this, early park visitors often called it Young Faithful Geyser. Unlike most geysers, the excitement at Bijou occurs when it stops. Actually Bijou's eruptions are fairly nice. The eruption can reach 15 feet and sometimes the eruption changes into a nice steam phase. Still everyone watches for Bijou to stop because this is when you may get a Giant Hot Period. Not all Giant Hot Periods result in an eruption of Giant but all Giant eruptions are preceded by a Giant Hot Period.

What to look for:

Ultimately the reason to watch Bijou is in the hopes of seeing a Giant Hot Period. Thus the observer is looking for a two or more minute stop in Bijou's activity.

Bijou stops for three different reasons:

First - Bijou stops during Giant's eruptions and does not restart until the system has started to recover from the eruption. The amount of time it takes for the system to recover can vary greatly but it usually takes over eight hours for the system to recover to the point that Bijou restarts.

Second - About five to six hours into a long mode eruption of Grotto Geyser (a Marathon eruption) Bijou will slow down and eventually stop. Bijou usually recovers and restarts about 4-6 hours after Grotto stops. During periods of frequent hot periods, Giant will often have a hot period at about the time that Bijou recovers.

Third - Bijou can have a PAUSE in its activity. A pause occurs when all splashing from Bijou stops. Assuming that Bijou is not pausing for either of the first two reasons, the reason that Bijou pauses is because the water levels on the Giant Platform are rising. The initial stages of the rising water can be hard to see from the boardwalk but Bijou's Pause indicates the rising water levels. Eventually, if the pause lasts long enough, the rising water levels can be seen in Mastiff Geyser and if a hot period results, in the many platform vents.

Catfish Geyser: [Map]

Catfish Geyser often erupts for short periods of time to about 10 feet. These small eruptions can occur during a Giant Hot Period but do not seem to have much significance to the Hot Period. They also occur outside of the Hot Periods. For the most part none of these eruptions are too inspiring. This can all change, though, during a Mastiff Function eruption of Giant Geyser. During some Mastiff Function eruptions, Catfish will join Mastiff and Giant in the eruption and erupt in a narrow jet for as many as 5 minutes and up to 75 feet tall.

Giant Geyser: Click for more information.

Mastiff Geyser: [Map]

At times, Mastiff has frequent boiling and splashing "eruptions" These "eruptions" are usually very small but sometimes reach 5 feet. For the most part, this activity signifies little and goes virtually unnoticed.