Black Opal Pool is a large murky blue pool with water flowing into other pools nearby. Soft sinter and sparse vegetation surrounds the area of the pool. Edges of the pool have dark thermophile material and the outflow from the pool travels down a slight hill forms braided channels of orange and green thermophiles. Black Opal Pool formed from a series of steam explosions in 1934, and more recently had smaller explosive activity in 2005 and 2006.

Black Opal Pool has an average temperate of 98.2°F (36.8°C), an average pH of 8.7, and an average conductivity of 2089 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.