There are two vents in Twilight Spring
, both geysers. The larger (east) vent has an irregular, elongated shape and is surrounded by a shallow pool edged by scalloped sinter, with a few isolated sinter deposits closer to the center. Orange and brown cyanobacteria inhabit adjacent, cooler pools. The smaller west vent is more symmetrical, about 2 feet in diameter, and has a narrower sinter ring. Both pools are sometimes empty, and when full both produce small eruptions lasting a few minutes.
Just beyond Twilight Spring the path reaches a four-way intersection, in the middle of the Sawmill Group of thermal features, many of which are seen along the right fork, which makes a short loop. The left fork heads southwest, crosses the Firehole River and links with the return part of the main Upper Geyser Basin Loop, and it is logical to visit the few pools along the section east of the river at this point; first is Churn Geyser
Back to map of the Upper Geyser Basin