The Grand Prismatic Spring is unlike anything you’ve ever seen. Not only is it the largest hot spring in the United States, but it has the most amazing rainbow color, starting with a deep blue center and radiating outward in a brilliant array.
The colors come from thermophiles, or heat loving microorganisms, that thrive at high temperatures. At the center, the 160 °F water is too hot for anything to thrive, allowing you to see the true color of the spring. But as the water cools toward the edges, the different thermophiles thrive, producing their amazing display of color.