[3] In 1892 Robert W. Wood, an American optical physicist, used the spring for a prank.

He stealthy dissolved a pint of fluorescein in the pool to surprise several witnesses with unusually colorful water.

[1] The spring gets its name from the emerald green color of the water created by sunlight filtering through the water, giving the light a blue color, and reflecting off the yellow sulphur creating the green hue.

[5] While Emerald Spring is a mostly calm pool, which usually only has a few bubbles rising to the surface, it does experience periods of turbidity and small 3-foot (1-m) high eruptions.

In 1931, Emerald experienced a period of extremely vigorous activity with eruptions measuring 60 to 75 feet (18.2–22.9 m) in height.