Scientists from the Brandenburg University of Applied Sciences in Germany and Montana State University teamed up with the sole purpose of finding a rational explanation for the colors that Yellowstone’s hot springs display.
The world’s largest hot springs and geysers can be visited at the Yellowstone National Park. These sites were the reason for establishing the park in 1872, thus becoming the first National Park in the United States. The colors created by these hot springs are one of the main reasons they became famous worldwide. This spectacle is known to emerge from the complex interaction between different types of bacteria and the underwater vents.
However, there were no explanations as to how chemical and physical variations create and influence this phenomenon.
This is where the mixed German-American team came into play. The members are: director of Montana University’s Optical Technology Center Joseph Shaw and his Ph.D. student Paul Nugent along with German colleague Michael Vollmer who co-authored the research paper. Michael Vollmer is also a professor at the aforementioned university.
The team came up with a less than intricate mathematical model that explains how this unique display of colors came to life. It can recreate the way geysers looked in the past, in a period when habits such as throwing coins or garbage into these springs were very rare.
This one-dimensional model was established on the basis of light propagation. Based on this, they performed optical measurements at the hot springs. The researchers succeeded in recreating the colors and optical features found at the geysers. The series of measurements conducted revealed specific spectral reflections caused not only by microbial mats or scattering of water but also by their optical absorption. They also recorded “the incident solar and diffuse skylight conditions”.
Their research consisted of examining a number of pools including Morning Glory Pool, Sapphire Pool and Grand Prismatic Spring. Handheld spectrometers were used, along with SLR cameras for digital imaging and infrared cameras for “non-contact measurement of the water temperatures.”
Their findings described a link between the shallow water temperature, bacterial population and the consequential color pattern. They also discovered that the colors that derived from the deeper part of the springs were caused mainly by “absorption and scattering of light in the water.”
The model, together with pictures taken at the springs appeared in the Dec. 19 issue of Applied Optics, a journal published by The Optical Society (OSA).
Image Source: Eastern Illinois University