Liberty Pool

Liberty Pool is one of the most intriguing hydrothermal features in Yellowstone’s Upper Geyser Basin, offering a vivid example of how dynamic and adaptable the park’s geothermal systems can be. Unlike the more visually dramatic pools and geysers that surround it, Liberty Pool tells a quieter but scientifically important story about change over time. 

Historically, this pool was significantly hotter, and during that period it exhibited the clear, vibrant blue color typical of high-temperature hot springs. Such blue coloration is caused by deep, mineral-rich water where only the most heat-tolerant thermophiles are capable of surviving. The temperature once suppressed biological growth, giving the pool a pristine, glass-like appearance.

Liberty Pool

Quick Reference: Liberty Pool

Feature	Details
Location	Upper Geyser Basin, Yellowstone National Park
Type of Feature	Hot Spring (formerly hotter with blue water, now cooler with algae growth)
Last Known Eruption	1888
Current Appearance	Algae mats on surface, grass growing to the edges, resembles a calm pond-like pool
Average Temperature	100.6°F (38.1°C)
Average pH	8.4 (alkaline)
Average Conductivity	1439 μS/cm
Scientific Importance	Demonstrates dynamic cooling and biological takeover in changing geothermal systems
Safety Note	Water is still hot; ground around the pool is fragile and dangerous

The pool’s last recorded eruption occurred in 1888, marking the end of its active eruptive period. Since then, its activity has been quiet, with no modern eruptions documented. Scientists consider Liberty Pool an important reminder that Yellowstone’s hydrothermal network is constantly shifting, influenced by underground water movement, pressure changes, seismic activity, and chemical evolution. Features that once erupted powerfully can become quiet and cool, while quiet pools may unexpectedly awaken again.

Liberty Pool’s water chemistry offers additional insights into its current condition. It maintains an average temperature of 100.6°F (38.1°C), which is warm enough to support microbial life but significantly lower than many nearby geysers and springs that exceed the boiling point. The pool has an average pH of 8.4, placing it in the alkaline range, and an average conductivity measurement of 1439 μS/cm, reflecting its dissolved mineral content.

Today, Liberty Pool looks very different from its earlier state. Its waters have cooled enough to allow algae mats to grow across the surface, creating a noticeably green and brown layer that moves gently with convection currents. Grass and other small plants now grow right up to the edges of the pool, softening the landscape and making the feature blend more closely with the surrounding terrain. This shift has transformed Liberty Pool from a classic high-temperature hot spring into a unique hybrid feature that visually resembles a small pond, even though it still maintains geothermal activity beneath the surface. Despite being cooler than most nearby springs in the Upper Geyser Basin, Liberty Pool remains a functioning hot spring and should never be mistaken for safe water. Like all hydrothermal features, it contains unstable and thin crusts around its perimeter that can be dangerous.