Yellowstone's Striking Springs Explained

Yellowstone National Park may be notorious for its brightly colored geothermal springs, but it's human meddling not Mother Nature that's responsible for the tourist attraction. Researchers at Montana University's Optical Technology Center and the Brandenburg University of Applied Sciences were able to turn back the clock – virtually, at least – to show what the natural pools would have been like decades ago, before trash, coins, and rocks tossed in by park visitors messed up the geothermal balance. Turns out, they really should be a whole lot more blue, something we can see today with a little juggling of digital cameras and temperature probing.

The Grand Prismatic Spring in Yellowstone is one of the National Park's most popular attractions, the largest hot spring to be found in the US, and the third largest in the world. Its colors stem from variations in bacteria growing around the edges of the water, changing according to the temperature that naturally fluctuates over the course of a year.

However, since human visitors have increased, unnatural reasons for the changing colors have had a greater impact too.

Visitors throwing in coins, rocks, and other detritus have lowered the temperatures, reducing the proportion of blue water visible, and increasing the red and orange rings.

Using data gathered by DSLRs and long-wave infrared thermal imaging cameras, along with spectrometers, the scientists were able to cook up optical processing algorithms that can show how the water would have looked in previous decades. By taking into account absorption and scattering of light molecules in water, as well as how the microbial mats and the pools' surface reflect, with temperature factored in, they came up with an image of how the Morning Glory Pool would've looked in the 1880s and 1940s.

Turns out, what they should look like is a more consistent blue, with the color fringing around the very edges rather than squeezing the deeper hue into a pupil in the middle.

It's unclear at this point whether the temperature of the pools will ever rise sufficiently to restore the original colors, which would require a significant change in park visitor behavior among other things.

SOURCE Applied Optics

IMAGE Jim Peaco, National Park Service