Why are hot springs so blue?

Microbial mats of heat-loving archaea (single-celled, bacteria-like organisms) cling to the edges, with different species congregating at different temperatures and forming the spring's outer rainbow hues. It's too hot for these tiny guys toward the center, leading to the rich, sterile blue tones found there.



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Many of the bright colors found in Yellowstone's hydrothermal basins come from “thermophiles” — microorganisms that thrive in hot temperatures. So many individual microorganisms are grouped together—trillions! —that they appear as masses of color.

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1. Norris Geyser Basin, Yellowstone. This tallest geyser in the world set the highest temperature ever recorded in the park. It's so far above sea level that the boiling point is 199°F rather than the sea-level 212°, but a hole drilled by scientists to 1,087 feet deep found a temperature of 459°F.

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The water in Yellowstone looks pristine and clear, but don't be fooled to think that it is clean and safe to drink on it's own. Because of the park's immense wildlife populations, there are animals constantly drinking, defecating and dying in and around these waters.

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Conundrum Hot Springs, Aspen, Colorado At the end of the trail, there is a cabin and thermal springs where you can soak and take in all that surrounds you.

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Hot springs are heated by geothermal heat—heat from the Earth's interior. In volcanic areas, water may come into contact with very hot rock heated by magma. Hot springs in active volcanic zones may produce superheated water, so hot that immersion can result in injury or death.

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We recommend getting out of the water for 5 minutes every 15 minutes or so. This largely depends on the temperature of the pool you're in. You might need to get out more often in a hotter pool and less in a mild pool. Listen to your body.

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Unfortunately, this means not all primitive hot springs are safe to swim in, with many boasting dangerous levels of algae or bacteria. Luckily, these dangerous conditions are rare, and most primitive hot springs undergo natural purifying processes that ensure their clean and safe swimming conditions for visitors.

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