Emerald Spring

Emerald Spring is a 27-foot-deep hot spring in the wooded Back Basin of Norris Geyser Basin. People stop for the clear blue-green water and pale mineral rim; this is a color-focused spring, not a geyser with a predictable eruption show. Stay on the boardwalk and designated trail: the water is close to boiling and can cause severe burns.

The Norris Museum parking area off Grand Loop Road serves the basin, and restrooms are at the lot. Emerald Spring is within Back Basin, whose full circuit is 1.5 miles over boardwalk and bare ground. That distance covers the whole route, not a separately measured walk to this spring. Continue around the loop if you want more scattered thermal features; road access to Norris changes seasonally, especially in winter.

For a photo, frame the pale sulfur-colored rim around the blue-green water from the boardwalk. The reflected color shifts with the light, so treat evening reflections as a possibility rather than a guarantee, and don’t step off the path for a cleaner angle.

Yellow sulfur deposits line the pool, while reflected blue light passes through the water; together they create its green-blue appearance. At about 27 feet deep and close to boiling, it is also a harsh environment where only the most heat-tolerant microbes survive. Some use sulfur for energy, while others use the byproducts of those reactions.

Emerald Spring sits among the wooded thermal features of Norris’s Back Basin. Hydrothermal activity in Norris has been underway for at least 115,000 years. Faults intersect a ring fracture from the Yellowstone caldera’s formation about 600,000 years ago, helping explain why this basin holds such a varied collection of hot springs, geysers, and other thermal features.