A large colorful pool, Mirror Pool is deep and clear blue at the center with a hard sinter shelf around the edge of the pool. The shallow waters of the sinter shelf holds yellow and orange thermophiles. The hard sinter surrounding the pool forms a small rim, and fractured and soft sinter with vegetation exist just outside of the rim.

Mirror Pool has an average temperate of 174.9°F (79.4°C), an average pH of 8.1, and an average conductivity of 1977 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.