Sunset Lake

Sunset Lake in Yellowstone National Park is one of the most visually striking hydrothermal features in the Black Sand Basin, a region known for its vivid colors and dramatic geothermal activity. Unlike the quiet lakes that many imagine when hearing its name, Sunset Lake is a large and intensely colorful hot spring that immediately draws attention with its deep blue center and radiant outer edges. 

The pool appears almost perfectly calm on the surface, yet beneath that calm lies constant boiling activity driven by the immense heat circulating through the Yellowstone Caldera’s volcanic plumbing system. Although the waterline rests level with the surrounding ground surface, Sunset Lake often overflows, sending mineral-rich water gently across its shallow edges and contributing continuously to the formation of new crusts of sinter around the pool.

Sunset Lake

Quick Reference: Sunset Lake

Category	Details
Location	Black Sand Basin, Yellowstone National Park
Type of Feature	Hot spring with historic eruptive activity
Water Temperature	Average 157.5°F (69.7°C)
Water Appearance	Deep blue center with yellow and orange thermophiles around the edges
Activity Level	Constant boiling movement beneath the surface; previous eruptions recorded
Last Recorded Eruption	2003
Water Chemistry	Average pH 7.7; conductivity 2243 µS/cm
Accessibility	Easily accessible via boardwalk in Black Sand Basin
Trail Difficulty	Very easy walk suitable for most visitors
Unique Feature	Overflows onto surrounding sinter shelf and displays vivid color bands resembling a sunset
Best Viewing Style	Stand back and observe color transitions and moving convection currents
Visitor Experience	Usually calmer than nearby major geysers; picturesque, peaceful atmosphere
Safety Reminder	Water is dangerously hot; remain on boardwalks at all times

The lake’s extraordinary palette of color is created by thermophiles, heat-loving microorganisms that thrive in water temperatures far beyond what most life can withstand. In the shallower regions surrounding the center, rings of yellow and bright orange thermophiles grow in wide bands, forming a gradient that resembles a sunset melting across the water’s surface. The center, where temperatures are highest, remains a deep blue because the heat prevents most microorganisms from surviving there. This dramatic contrast of hues is one of the reasons visitors often find Sunset Lake unforgettable, especially when sunlight reflects off the steam drifting above it and intensifies the warm color spectrum around the edges.

Though peaceful in appearance, Sunset Lake has a history of unpredictable behavior. It has experienced previous minor eruptions and long periods of vigorous boiling due to extremely high temperatures beneath the surface. The last documented eruptive activity occurred in 2003, a reminder that even features that look tranquil can be influenced by the powerful subterranean forces that define Yellowstone National Park. Watching the water at Sunset Lake, one can often see ripples and swirling motion created by convection currents, demonstrating that the pool is never truly still.

Scientific measurements reveal just how extreme the environment of Sunset Lake is. The lake’s average water temperature is approximately 157.5°F (69.7°C), a level far beyond what is safe for human contact. The average pH is recorded at around 7.7, which is relatively neutral compared to many of Yellowstone’s acidic springs, and the average conductivity measures 2243 µS/cm, indicating a high concentration of dissolved minerals carried from deep underground. These chemical and thermal conditions shape not only the pool’s remarkable colors but also its unique ecosystem.

While much of Black Sand Basin can feel busy because of its location near Old Faithful, Sunset Lake itself often feels quieter and more contemplative than many nearby features. The sounds of bubbling water and gently escaping steam combine with shifting vapor to create an atmosphere that feels almost dreamlike. Visitors who linger on the boardwalk frequently describe a sense of calm and wonder as they watch light play across the water, revealing new shades and patterns every few moments.