Grand Prismatic Spring.

The Grand Prismatic Spring in Yellowstone National Park is the largest hot spring in the United States, and the third largest in the world,^[1] next to those in New Zealand.

History

There is no doubt that many Native American people were aware of the Grand Prismatic Spring long before Europeans first saw it, but the first records of the spring are from early explorers and surveyors.

In 1839, a group of fur trappers from the American Fur Company crossed the Midland Geyser Basin and made note of a "boiling lake", most likely the Grand Prismatic Spring,^[2] with a diameter of .

In 1870, the Washburn Party, led by General Henry D. Washburn, visited the spring, noting a 50-foot (15-meter) geyser nearby (later named Excelsior^[3]).^[4]

Colour

An aerial view of Grand Prismatic Spring.

The vivid colors in the spring are the result of pigmented bacteria in the microbial mats that grow around the edges of the mineral-rich water. The bacteria produce colors ranging from green to red; the amount of color in the microbial mats depends on the ratio of chlorophyll to carotenoids. In the summer, the mats tend to be orange and red, whereas in the winter the mats are usually dark green.^[5] The center of the pool is sterile due to extreme heat.

The deep blue color of the water in the center of the pool results from a light-absorbing overtone of the hydroxy stretch of water.^[6] Though this effect is responsible for making all large bodies of water blue, it is particularly intense in Grand Prismatic Spring because of the high purity and depth of the water in the middle of the spring.

Physical structure

Grand Prismatic Spring and Midway Geyser Basin

References

External links

fr:Grand Prismatic Spring nl:Grand Prismatic Spring