A couple watches Sawmill Geyser erupt. Castle Geyser's cone can be seen in the background. Located at the intersection of the trail from Castle Geyser which crosses the Firehole river and the trail from Geyser Hill, this is an active geyser group and a little patience here can be rewarded with eruptions of several geysers.
Activity is cyclic.
Usually Sawmill, Tardy and Spasmodic have significant eruptions. However, sometimes, much less commonly, Sawmill seldom plays, durations for Tardy and Spasmodic shorten and Penta and Churn have significant eruptions. It is interesting to note that these geysers often play together. When the eruptions end the water drops in all the group leaving what looks like dry dormant craters. But if you wait a couple of hours the pools refill simultaneously and eruptions begin.