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, [cite web | title=Steam Explosions, Earthquakes, and Volcanic Eruptions—What’s in Yellowstone’s Future? | work=U.S. Geological Survey | url=http://pubs.usgs.gov/fs/2005/3024/ | accessdate=2005-09-14 ] 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, [cite web | title=VII. "The Fire Hole": Era of the American Fur Company, 1833-1840 | work=Colter's Hell & Jackson's Hole - The Fur Trappers' Exploration of the Yellowstone and Grand Teton Park Region | url=http://www.cr.nps.gov/history/online_books/grte1/chap7.htm | accessdate=2005-09-14 ] with a diameter of ft to m|300.

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 [cite web | title=Notes | work=Yellowstone National Park: Its Exploration and Establishment | url=http://www.cr.nps.gov/history/online_books/haines1/ieee.htm#2146 | accessdate=2005-09-14 ] ). [cite web | title=Part II: Definitive Knowledge - The Washburn Party (1870) | work=Yellowstone National Park: Its Exploration and Establishment | url=http://www.cr.nps.gov/history/online_books/haines1/iee2d.htm | accessdate=2005-09-14 ]

Colour

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. [cite web | author=Thomas D. Brock | title=Colorful Yellowstone | work=Life at High Temperatures | url= http://www.bact.wisc.edu/bact303/b4 | accessmonthday=September 14 | accessyear=2005 ] 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. [cite web | last = Braun | first = Charles L. | coauthors = Sergei N. Smirnov | year = 1993 | url = http://www.dartmouth.edu/~etrnsfer/water.htm | title = Why Is Water Blue? | accessmonthday = May 23 | accessyear = 2006] 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

The spring is approximately 250 by 300 feet (75 by 91 m) in size and is 160 feet (49 meters) deep. The spring discharges an estimated 560 gallons (2000 litres) of 160°F (71°C) water per minute. [cite web | year = 2006 | url = http://geyserstudy.computerpoint.net/geyser.aspx?pGeyserNo=GRANDPRISMATIC| title = Grand Prismatic Spring | work = Geyser Observation and Study Association (GOSA) | accessmonthday = May 23 | accessyear = 2006]

References

External links

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