Castle Group
and
Sawmill Complex
[ Castle Group - Map ] [ Sawmill Complex - Map ]
Castle Group: - Map
[Castle Group introduction provided by Kyle Chumbley.]
Castle Geyser is surrounded by a number of smaller geysers of which several are very active. The majority of the group lies on the same side of the Firehole River as Old Faithful, while on the other side are the Grand and Sawmill Groups. Castle itself is quite possibly the oldest geyser in Yellowstone, as suggested by its enormous cone. Most of the activity in this group occurs on or near the broad sinter mound crowned by Castle Geyser’s cone.
The more active members of the group are: Tortoise Shell Spring, Castle, Gizmo, Sprinkler, Spanker, Deleted Teakettle, and Tilt Geysers. Also in the group are Spatter and Chimney Geysers, and the Terra Cotta Springs. Crested Pool, a hot, active, and unfortunately deadly pool, is also in this group.
Castle Geyser: Click for more information.
Crested Pool is a beautiful blue, super-heated pool. Tragically, it is one of the thermal features in Yellowstone to have claimed a human life. It is always prudent to remember the dangers in the thermal areas.
Depending upon your definition of a geyser, Crested Pool is either a geyser or a pool which has periodic large heavy boils. I lean towards the geyser definition. Crested Pool is almost constantly in overflow over its built up, crested, edge. Every few minutes, it has heavy boils. Usually these boils only reach a few inches. Sometimes they reach a few feet. On rare occasions they reach over 10 feet. The larger boils build quickly and usually startle anyone standing nearby. After the larger boils, the pool drops below overflow and takes a few seconds to reach overflow again.
Gizmo Geyser: [Map]
Gizmo Geyser erupts from a collection of vents at the base of Castle's cone. Intervals range from 5-20 minutes, durations range from 1-5 minutes and heights range from inches to about 15 feet. The most noticeable thing about Gizmo's eruption is its loud steam-phase. The steam-phase come periodically and involve at least three of Gizmo's vents. It is during the steam-phase that Gizmo is its tallest with one vent reaching about 15 feet. Even if you are not watching for them, Gizmo's steam phases are loud enough to get your attention.
Tilt Geyser: [Map]
Tilt is a fun geyser. It is small, only often less than 3 feet tall, duration about 2 minutes and intervals in recent years when active of about 50 minutes. What makes Tilt Geyser so much fun are the interesting sounds it usually makes when it ends.
Tilt consists of three small surface vents. Two of these vents, the two that do most of the bursting during the eruption, are right below the fenced corner of the boardwalk past Castle Geyser and across from Crested Pool. These two ragged holes in the sinter are easy to miss. The third vent, and the one that makes the interesting sounds, is located about 10 feet to the right of the first two vents, closer to Castle.
The corner of the boardwalk, where Tilt is located, is a good place to wait for an eruption of Castle Geyser. Not only can you watch Castle from this location but you can also watch the activity on Geyser Hill and in the Sawmill and Grand Groups. This location provides one of the most wide reaching observation points in the geyser basin.
What to look for:
Tilt erupts with little forewarning. First, the two vents near the boardwalk begin gurgling. Within a minute or so the water rises into view. Sometimes the vents do little more than bubble before the water drains. Often though, the water will continue to rise and overflow, then the vents will start to burst. The height of the bursts vary greatly but can reach 6 feet. This often startles people standing nearby that have not been paying attention. Some of the water from the first two vents of Tilt flows into the third vent drowning that vent. The third vent sometimes sputters and bursts a little but often it doesn't even do this.
The eruption ends first in the two vents near the boardwalk. The bursting stops and they drain. Any bursting in the third vent also stops and the pool in the third vent becomes calm. Don't leave yet, the best is still to come. Then, as the steam in the plumbing system collapses, the third vent begins to drain. This collapse of steam causes a suction. Which in turn, often causes a strong whirlpool in the pool over the third vent and a sucking noise. This is one of the highlights of the eruption. The other highlight is the final drain of the pool. The pool drains with a loud and interesting gurgling noise. For being such a small geyser, Tilt is abnormally fun and always pleases those that get to see a good eruption.
Sawmill Complex: - Map
The Sawmill Group is possibly the most complex and active groups in the Upper Geyser Basin. All of its members are interconnected and other than Belgian Pool all are relatively frequently seen to erupt. Because of the high level of activity and interconnectedness, it takes years of study to begin to understand the interrelationships of the geysers in the group.
The activity in the complex is cyclic. Usually the activity is dominated by Spasmodic, Tardy and Sawmill with Penta being infrequently seen. This is known as the Sawmill Mode. More rare is the Penta-Churn Mode. During this mode, Sawmill is rarely seen but Penta plays and sometimes Churn is seen.
Churn Geyser: [Map]
Churn is a small, about 15 feet tall, fountain-type geyser. It erupts when the Sawmill complex is in the Penta-Churn Mode. Even at these times it can be rare. For periods in 1996 and 1997 though, Churn dominated the Sawmill complex. At these times, Sawmill was seen infrequently and Penta was seen even less.
Churn can erupt in a series, as many as 9 eruptions have been seen in recent years. These eruptions occur about 15 minutes apart and each lasts about 90 seconds.
Old Tardy Geyser: [Picture] [Map]
The eruptions of Old Tardy look similar to those of Tardy Geyser but the craters look different. Old Tardy is a fountain-type geyser. Intervals range from minutes to hours, durations range from seconds to hours, though a few minutes is more the norm. The maximum height is 10-15 feet.
The water level in Old Tardy follows the same rises and falls as the rest of the Sawmill Complex.
Penta erupts from a small cone only a few feet from the boardwalk. Usually it is a fairly infrequent performer but during the Penta-Churn mode, it can be seen as often as two or more times per day. Eruptions consist of jetting from the main vent up to 25 feet tall and splashing and jetting from the other vents to as much as four feet. Penta's durations range from 30 minutes to over two hours.
Penta has a second type of eruption, which consists mainly of steam and small amount of water. These "steam-phase" eruptions are fairly rare. They often occur during a deep drain and usually last less than 10 minutes.
What to look for:
While more common during the Penta-Churn Mode, Penta eruptions can occur during other modes of the complex as well.
Non steam-phase eruption of Penta start when the water levels in the complex are rising. Usually after Spasmodic and Tardy and sometimes Old Tardy have already started but before anything else in the complex has started erupting. It is often a race to see if Penta will erupt or if Sawmill will erupt. An eruption of either dooms the other.
There are two vents on the boardwalk side at the base of Penta's cone. It is possible to watch the water level rise in these two vents. Before an eruption, the water level will eventually rise until it forms a shallow pool that almost reaches the boardwalk and starts overflowing towards Sawmill. Convection currents form over the vents and bubbles start to rise. It is possible for the water level to drop at this point only to rebound a few minutes later or to just drop and disappear.
It is when the water level is high, there is runoff and there is bubbling over the two vents that the eruption can occur. Unfortunately, even at this late stage, Sawmill can still steal the glory. While the water is rising at Penta, it is also rising at Sawmill. If Sawmill erupts first, Penta will begin to drain and not erupt.
If Penta erupts first, the water levels in the complex may appear to hold for as much as an hour but eventually they will slowly begin to drop.
Penta often stops within a few minutes of the end of Spasmodic's eruption.
Sawmill Geyser: [Pictures][Map]
Sawmill is the largest member of the Sawmill Complex. It is a fountain-type geyser, its bursting eruptions playing through a funnel shaped pool. Typical intervals are one to three hours. Durations can range from 9 minutes to more than 4 hours with most in the 30 to 50 minute range. Heights can exceed 35 feet. When the complex is in the Sawmill Mode, Sawmill Geyser is usually in eruption about one third of the time.
Sawmill was named for the whirring noise it makes during its eruption and/or for the rotary motion in its pool during the eruption. Either way, Sawmill is an enjoyable geyser. It is fun to watch and to hear.
What to look for:
After an eruption, Sawmill drains, leading many first-time visitors who see the empty crater, to believe that the geyser is dead.
Prior to an eruption, Sawmill, along with the other features in the complex,begin to slowly fill. At this time, Tardy and Spasmodic often start to erupt. preceding Sawmill. As the water rises, a battle often takes place between Penta and Sawmill. Whichever erupts first dooms the other, causing the other to drain without erupting.
Just prior to the eruption, Sawmill will be near or just at overflow. At this time, bubbles start rising in the pool. At first the bubble collapse before they reach the surface but eventually they reach the surface, at which point the eruption is usually near.
After an eruption of Sawmill drains and all of the other features in the complex drop from a few inches to many feet. In general, the longer the eruption the deeper the drain. A long eruption of Sawmill causes a "deep drain" which often accompanies rare behavior in some of the other members of the complex.
Spasmodic Geyser: [Pictures][Map]
Spasmodic is a fun geyser. It erupts from at least 20 vents. During the eruption, the activity overall is nearly constant but the activity cycles through the various vents every few minutes. Some vents only erupt a few inches while the tallest can reach ten feet. Intervals are about 1 to 3 hours. Durations range from minutes to hours. Spasmodic is in eruption about one third of the time.
Spasmodic is active during both the Sawmill Mode and the Penta-Churn Mode. In either case, Spasmodic usually precedes these other geysers.
Tardy Geyser is a smaller version of Sawmill Geyser. Like Sawmill, it is a fountain-type geyser, its bursting eruptions playing through a funnel shaped pool. Typical intervals range from minutes to hours. When in the Sawmill Mode, durations are usually measured in minutes but in the Penta-Churn Mode the may last hours. Maximum heights are usually about 10 feet but during a "deep drain" steamy bursts can reach 20 feet.
The name Tardy has been moved around a bit during the history of the park. It started on the current feature but at various times in the early history of the park was moved to what are now Turban Geyser and Old Tardy Geyser.
Uncertain Geyser: [Picture] [Map]
The vent of Uncertain Geyser lies nearly hidden in the low sinter mound behind Sawmill Geyser. If you don't know where the small round vent is located, it can be hard to see.
Uncertain is a cone-type geyser. Its eruptions are intimately connected to the Sawmill Complex cycles. Most often Uncertain erupts when the complex is in a "Deep Drain". Uncertain erupts in a very steamy jet to 10 to 15 feet for a duration of 2 to 5 minutes. The eruptions is concluded by a weak steam phase. Prior to the eruption, Uncertain frequently splashes slightly. This is one of the few times outside the eruption that water can be seen.
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Area - Map ]
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Group - Map ] [ Grotto
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Glory Group - Map
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