Emerald Spring

Overview

Emerald Spring is a vivid, emerald-green hot spring tucked into the Back Basin of Norris Geyser Basin. Its color pops even on overcast days—blue water over a yellow sulfur lining creates that unmistakable green glow. The pool is about 27 feet deep and the water at the surface is near boiling, so this is strictly a look-don’t-touch stop.

Why it’s emerald (and what that says about the chemistry)

Hot spring water appears blue as it absorbs other wavelengths of light. At Emerald Spring, yellow sulfur deposits line the pool. Blue plus yellow reads as emerald to your eyes. The water here is not just hot; it’s also acidic. Surveys have measured near‑boiling temperatures and low pH, and only the hardiest thermophiles can tolerate the hottest water. Cooler edges host more colorful microbial mats.

Geologic setting: hot, dynamic, and ever-changing

Norris is among the park’s hottest and most chemically diverse basins. Emerald Spring is a hot spring (not a geyser), meaning its underground “plumbing” is open enough for water to circulate instead of erupt. Norris is also seismically active, so features can shift in behavior during thermal disturbances—another reason every visit can feel a little different.

What you’ll see

• A luminous, glassy green pool framed by delicate thermal ground.
• Occasional wafts of hydrogen sulfide—a classic “rotten egg” reminder you’re standing over powerful hydrothermal chemistry.
• Boardwalk vantage points that make it easy to linger for photos and move on to marquee neighbors like Steamboat Geyser.

How to visit

Emerald Spring sits along the Back Basin loop (about 1.5 miles of boardwalks). If you start the Back Basin loop by going left from the museum, you’ll reach Emerald Spring early in the walk. It pairs naturally with a quick spin through Porcelain Basin first, then a fuller wander through Back Basin.

Safety essentials

Stay on the boardwalks and designated trails—ground here can be thin and the water can severely burn. Supervise kids closely and don’t run or shove. Never disturb hydrothermal mats or toss anything into the water.

Best time to visit

Go early to beat the boardwalk crowds and enjoy cooler temps. Morning light is often soft and flattering for photos; just know steam can hang thicker in cool air. Late afternoon can also be lovely when the day-tripper rush eases.

Wildlife etiquette

Give wildlife space—at least 100 yards for bears and wolves. If you stop to watch, pull completely off the road and never block traffic. Don’t feed animals and don’t throw objects into thermal features.