USA - Wyoming - Yellowstone National Park (4) - Grand Prismatic Spring

Yellowstone National Park, Wyoming

Yellowstone National Park is a nearly 3,500-sq-mile wilderness recreation area atop a volcanic hot spot. Mostly in Wyoming, the park spreads into parts of Montana and Idaho, too. Yellowstone features dramatic canyons, alpine rivers, lush forests, hot springs, and gushing geysers. Pictured here is the World Famous Grand Prismatic Spring which is the largest hot spring in the United States, and the third largest in the world.

Sent by Lily from California, USA.

The Grand Prismatic Spring in Yellowstone National Park is the largest hot spring in the United States, and the third largest in the world, after Frying Pan Lake in New Zealand and Boiling Lake in Dominica. It is located in the Midway Geyser Basin.

Grand Prismatic Spring was noted by geologists working in the Hayden Geological Survey of 1871, and named by them for its striking coloration. Its colors match most of those seen in the rainbow dispersion of white light by an optical prism: red, orange, yellow, green, and blue.

The first records of the spring are from early European explorers and surveyors. In 1839, a group of four trappers from the American Fur Company crossed the Midway Geyser Basin and made note of a "boiling lake", most likely the Grand Prismatic Spring, with a diameter of 300 feet (90 m). In 1870 the Washburn–Langford–Doane Expedition visited the spring, noting a 50-foot (15 m) geyser nearby (later named Excelsior).

The bright, vivid colors in the spring are the result of microbial mats of thermophilic bacteria around the edges of the mineral-rich water. The mats produce colors ranging from green to red; the amount of color in the microbial mats depends on the ratio of chlorophyll to carotenoids and on the temperature gradient in the runoff. In the summer, the mats tend to be orange and red, whereas in the winter the mats are usually dark green (read more).