Colors of Grand Prismatic Spring
July 07, 2011
The photos above were taken at Yellowstone National Park while on a walkway at the Grand Prismatic Spring. As I approached, I saw very distinctive rainbow colors in the steam rising from the spring (top photo). At first, I thought I was observing a typical mist bow; similar to the one I noticed the day before when visiting the Upper and Lower Falls of the Yellowstone Canyon. As I progressed around the trail, the colors remained even though my perspective changed relative to the Sun. It seemed that I had somehow maintained just the right perspective to allow the colors to endure. The true source of the colors became evident at the head of the boardwalk. The intense blue color in the center is due to sunlight being scattered by very fine particles suspended in the water and likely also by water's intrinsic blue color. The bottom photo shows the source of the yellow, orange and brown coloration. These colors are caused by bacteria and thermophiles: heat-loving algae that contain colorful pigments. Each color of algae is specific to a particular temperature range radiating from the center of the hot spring -- the water gradually cools as it flows outward from its source. So, the conspicuous colors of the steam resulted not from rainbow optics but rather from the refection off the water in the pool onto the rising column of steam. Photos taken on June 5, 2011.
Photo details: Top - Camera Maker: NIKON CORPORATION; Camera Model: NIKON D50; Focal Length: 55mm (35mm equivalent: 82mm); Aperture: f/10.0; Exposure Time: 0.0040 s (1/250); Exposure Bias: none; Metering Mode: Matrix; White Balance: Auto; Flash Fired: No (enforced); Orientation: Normal; Color Space: sRGB. Bottom - same except Focal Length: 18mm (35mm equivalent: 27mm); Aperture: f/11.0; Exposure Time: 0.0025 s (1/400).