A large colorful pool, Sunset Lake is deep and blue at the center. Along the shallow shelf of sinter surrounding the pool grow yellow and then orange thermophiles. Sunset Lake has had previous eruptions and constant boiling activity due to its high temperatures, with the last eruption recorded in 2003. The pool overflows, but lays in line with the ground surface.

Sunset Lake has an average temperate of 157.5°F (69.7°C), an average pH of 7.7, and an average conductivity of 2243 uS/cm.

Hot Springs

Hot springs are the most common hydrothermal features in Yellowstone. Their plumbing has no constrictions.

Superheated water cools as it reaches the surface, sinks, and is replaced by hotter water from below.

This circulation prevents water from reaching the temperature needed to set off an eruption.

Use Caution in Hydrothermal Areas

• Stay on boardwalks and designated trails.
• Hydrothermal water can severely burn you.
• Never run, push, or shove.
• Supervise children at all times.
• Do not scratch hydrothermal mats.

You are responsible for your safety.

Think safety, act safely. Yellowstone is a dangerous place.