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  Penta Geyser
Feature Type: Geyser
Geyser/Spring Type: Fountain geyser

Basin
Upper Geyser Basin
Complex
Grand and Castle Group

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.








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