While perhaps created by a thermal explosion, it appears Opalescent Pool no longer has its own source of hydrothermal waters but acts as a catch pool for Spouter Geyser. It's named after its opalescence coloring, formed by suspended silica particles in the water. The cooler waters allow for large areas of orange thermophiles to grow in the shallow water. The pool is deep and dark blue at the center with sinter steps forming the edges of the pool. The water flowing from Spouter Geyser continues to flow from Opalescent Pool into the river. Dead trees with silica-solidified bases surround the pool and stand in the runoff.

Opalescent Pool has an average temperate of 106.9°F (41.6°C), an average pH of 8.9, and an average conductivity of 2291 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.