Morning Glory Pool, Yellowstone National Park in the United States

wiki says.
Morning Glory Pool is a hot spring in the Upper Geyser Basin of Yellowstone National Park in the United States, similarity to the morning glory flower. The distinct color of the pool is due to bacteria which inhabit the water. Several entryways have been clogged due to objects being thrown in by tourists, reducing the hot water supply, and in turn altering the overall appearance of the pool.

On a few rare occasions the Morning Glory Pool has erupted as a geyser, usually following an earthquake or other nearby seismic activity. Several attempts by park officials to artificially induce eruptions to clear the pool of debris and clear blocked entryways have been met with mixed results.