As the largest hot spring in Yellowstone—and in the country—Grand Prismatic certainly lives up to the grand in its name. At 121 feet deep, this naturally plumbed spring is known for its vivid colors, which have lent themselves so well to countless photos, postcards and paintings. But the scientific story behind its hues is even more remarkable than the imagination and artwork it inspires. Let’s take a look inside the spring’s depths.
Grand Prismatic looks like the Everlasting Gobstopper of geothermal features—you know, the candy that slowly dissolves layer by layer, changing flavors and colors as it goes. Except as each color layer changes in Grand Prismatic, it tells us a little bit about the changing temperature of the spring. And the colors share what critters live there.
If we start in the center and work our way outward, the spring tells a story of temperature. The water in the middle, that clear and brilliant blue, is the hottest. At 188 degrees Fahrenheit (87 Celsius), this water is too hot for just about any life to survive, except for organisms that eat inorganic material. After all, there’s nothing else in there for them to eat besides hydrogen gas—nothing else can survive long enough to become dinner.
From that clear sapphire blue, the colors of Grand Prismatic march on. In a rainbow that matches the color sequence of light refracted through a prism, it continues on to yellow, orange and red, in a color play stretching 300 feet (90 meters) across. Each color layer corresponds to a different temperature layer, as the water bubbles up from the depths of the spring, moving out across the surface as it cools, before sinking down again to reheat.
As each layer shifts color, we’re seeing the temperature drop, making for a more hospitable habitat for more microorganisms. It starts with yellow, where the water is still at 165 degrees Fahrenheit. That’s a barely tolerable temperature for Synechococcus, a type of Cyanobacteria that can live in some pretty wild conditions. But even as an extremophile, adapted to extremes of temperature humans couldn’t hack it in, this microscopic Cyanobacteria struggles with the bright sun and hot temperature. That’s why it produces carotenoids (the same pigment that makes carrots orange) as a sort of sunscreen.
Moving outward, each layer of color means the water temperature drops a little, inviting more forms of life. And each type of microorganism throws another pigment into the color pot, leading from yellow to orange, and then finally red.
The biology of spots like Grand Prismatic is interesting in its own right. But they can teach us more than just the obvious. What scientists learn by studying these extremes of earth’s environments can help them be better prepared to detect life on other planets, in outer space, or in the deepest reaches of the planet.
These are relatives of some of the earliest life forms on earth, living in similar conditions. What scientists observe in them can share volumes about the past.
When you visit Grand Prismatic, you have a few options. You can walk the boardwalks that rose just above the water for an up-close look. Of course, you don’t want to touch this scalding and sensitive spot. And while drones are not allowed in the park, you still have an option for a bird’s-eye view. Take the trail up the bluff to see the color show from above.
When your Yellowstone adventures wind down for the day, find a spot to kick back and share your stories around the campfire. Highline Adventures properties can help you unwind and embrace sustainable living. Book your spot, and explore.