Opal Pool, Hot spring in Midway Geyser Basin, Yellowstone National Park, Wyoming, US.
Opal Pool is a hot spring in Midway Geyser Basin within Yellowstone National Park that erupts regularly with geothermal water. The mineral-rich water creates an unusual appearance that shifts depending on temperature and mineral content.
The pool began erupting in 1947 with sporadic activity, then paused between 1953 and 1979. After 1979, eruptions occurred regularly until the basin drained completely in 2005.
The pool takes its name from the opalescent shimmer visible in its water under certain light angles. Visitors notice this color shift especially when sunlight hits the water from different directions.
Access is via paved walkways that start directly from the Midway Geyser Basin visitor area. It is important to stay on marked paths and follow park safety rules since the water is extremely hot.
The basin drained completely in 2005 and refilled only in 2008, a rare transformation for a geothermal spring. After this emptying, the water now displays a green color and eruptions can shoot up to 80 feet high.
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