Emerald Pool

Overview

Emerald Pool sits along the Black Sand Basin boardwalk, a short hop from the Old Faithful area. It earned its name in 1878 for a blue-green tint that once wowed early visitors and filled postcards. Today, it’s still a standout stop—just with a different palette.

What You’ll See

Expect a broad, steaming hot spring framed by thin sinter and bands of thermophiles. The pool is roughly 27 by 38 feet across, about 25 feet deep, and far too hot and fragile to touch. On clear days, the color bands pop; on cooler mornings, steam can drift across the surface and soften the view.

Why the Colors Changed

Emerald Pool’s famous green came from the blue of deep, clear water mixing with a yellow fringe of heat-loving microbes. As temperatures dropped over time, a different microbial community took hold, shifting the pool toward orange and brown tones. Even small disturbances—like debris tossed in—can alter temperatures and biology, so staying on the boardwalk and leaving nothing behind genuinely matters.

How to Visit

Park at the Black Sand Basin lot and stroll the easy boardwalk loop. Emerald Pool is one of several features here, so it’s an efficient stop you can pair with Old Faithful and the wider Upper Geyser Basin.

What Else Is Nearby in Black Sand Basin

You’ll pass constantly chattering Spouter Geyser, the pale, shallow Opalescent Pool (look for “bobby sock” trees), Cliff Geyser along Iron Creek, plus the broad Rainbow Pool and Sunset Lake with colorful microbial mats between them. It’s a compact sampler of Yellowstone’s hydrothermal variety.

Best Time to Visit

Midday light usually brings out the strongest colors. If it’s a cool day, give the steam a few minutes to drift before judging the view. In peak season, arrive early or later in the afternoon for a calmer boardwalk experience.

Safety and Etiquette

Stay on the boardwalk—hydrothermal ground is thin and water can cause severe burns. Don’t throw anything into the pool; it changes the chemistry and can permanently affect the colors. Wildlife can wander through anytime—give them space and never approach.