Yellowstone’s Grand Prismatic

With temperatures that are so hot if touched by a human hand skin would melt right off the bone, it’s hard to imagine it also being one of America’s geologic and visual treasures. But it is!

First noted by early 1800’s European trappers (obviously discovered much earlier by Native Americans) as a “boiling lake with a diameter of 300 feet,” Grand Prismatic Spring, located inside Yellowstone National Park, has been luring and amazing visitors for well over a century by its dazzling blue center surrounded by rings of red to green.

“Nothing ever conceived by human art could equal the peculiar vividness and delicacy of color of these remarkable prismatic springs.”

-Ferdinand Hayden 1871

The Grand Prismatic Spring is the largest hot spring in the United States, measuring approximately 370 feet in diameter and over 121 feet deep. It is the third largest in the world, after Frying Pan Lake in New Zealand and Boiling Lake in Dominica.

We’ll be certain to stop and photograph the spring while on Backcountry Journeys Spring Comes to Yellowstone & Grand Teton tour & Yellowstone Wildlife Safari. While Grand Prismatic is one of the brightest highlights on this highlight-filled tour, it is obviously not the only of Yellowstone’s famous hydrothermal features we’ll visit, so hang onto your hats!

While this post will focus on Grand Prismatic, we still feel it in order to take a moment to talk about the different hydrothermal features found at Yellowstone, because while they are all marvelous, they aren’t all the same. Yellowstone features hot springs, mud pots, fumaroles, and probably the most famous of the features, geysers!

What are they and how are they different?
(The following science comes from

Hot Springs: Hot springs are the most common hydrothermal features in the park. Their plumbing has no constrictions. Superheated water cools as it reaches the surface, sinks, and is replaced by hotter water from below. This circulation, called convection, prevents water from reaching the temperature needed to set off an eruption.

Mud Pots: Mudpots are acidic features with a limited water supply. Some microorganisms use hydrogen sulfide, which rises from deep within the earth, as an energy source. They help convert the gas to sulfuric acid, which breaks down rock into clay. Various gases escape through the wet clay mud, causing it to bubble. Mudpot consistency and activity vary with the seasons and precipitation.

Fumaroles: Fumaroles, or steam vents, are the hottest of the hydrothermal features. The limited amount of water flashes into steam before reaching the surface. The result is a loud hissing of steam and gases.

Travertine Terraces: Travertine terraces are formed from limestone (calcium carbonate). Water rises through the limestone, carrying high amounts of dissolved calcium carbonate. At the surface, carbon dioxide is released and calcium carbonate is deposited, forming travertine, the chalky white rock of the terraces. Due to the rapid rate of deposition, these features change often and fast.

Geysers: Geysers are hot springs with constrictions in their plumbing, usually near the surface, that prevent water from circulating freely to the surface where heat would escape. The deepest circulating water can exceed the surface boiling point. Surrounding pressure also increases with depth, similar to the ocean. Increased pressure exerted by the enormous weight of the overlying water prevents the water from boiling. As the water rises, steam forms. Bubbling upward, steam expands as it nears the top of the water column. At a critical point, the confined bubbles actually lift the water above, causing the geyser to splash or overflow. This decreases pressure on the system, and violent boiling results. Tremendous amounts of steam force water out of the vent and an eruption begins. Water is expelled faster than it can enter the plumbing system, and the heat and pressure gradually decrease. The eruption stops when the water reservoir is depleted or when the system cools.

Cool, no?

All these features are of course amazing in their own way, however, we’re going to focus this post on Grand Prismatic, which is a hot spring, so keep in mind some of the science on hot springs from the above paragraph.

(The following science is taken from

The otherworldly effect is caused by varieties of pigmented bacteria and microbes that thrive in the warm, mineral abundant waters surrounding the hot spring.

The hot spring radiates extremely hot water—and stunning prismatic color—from its center.

Water at the center of the spring, which bubbles up 121 feet from underground chambers, can reach temperatures around 189 degrees Fahrenheit, which makes it too hot to sustain most life. Because there’s very little living in the center of the pool, the water looks extremely clear and has a beautiful, deep-blue color.

But as the water spreads out and cools, it creates concentric circles of varying temperatures, and these distinct temperature rings create a very different environment inhabited by different types of bacteria.

And it’s the different types of bacteria that give the spring its prismatic colors.

Moving outward from the yellow band, the temperature of the hot spring begins to cool, and as the temperature cools, a more diverse set of bacterial life can flourish. The net result of this color diversity is the orange color that you see in pictures—it’s not that every bacterium manifests as orange individually, but that the composite color of all the different bacteria seen together is orange. And that orange color, like the yellow in the ring next to it, comes from carotenoids, which these bacteria produce to help shield themselves from the harsh light of Yellowstone’s summer sun.

The outermost ring is the coolest, at around 131°F, and home to the most diverse community of bacteria. As even more organisms are able to live in the outermost ring, the mix of their various carotenoids produces the darkest color of all—the kind of red-brown that you see in photos.

It truly is a sight to behold and one we tend to spend quite a bit of time on during our trips.

“Life becomes a privilege and a blessing after one has seen and thoroughly felt these incomparable types of nature’s cunning skill.”

-Hayden, 1871

Kenton Krueger







Kenton Krueger has spent the past several years guiding backpackers, hikers, and photographers into the wild places of the American West such as Grand Canyon, Yellowstone, Yosemite, Glacier, Katmai, Zion, Bryce Canyon, Arches, Canyonlands National Parks, as well as internationally in Costa Rica & Brazil. In addition to backpacking and camping, his adventures include rock climbing, exploring the slot canyons of southern Utah, mountain biking, and bagging 14ers in Colorado’s San Juan Mountain Mountain Range. Kenton is a trail runner, former pilot, and spent roughly five years writing and photographing for the award-winning Omaha World-Herald newspaper, out of his hometown, Omaha, Nebraska. Kenton looks forward to utilizing his years of trip leading and guiding experience, combined with his passion and experience behind the lens, to provide memorable and unforgettable experiences at the wild places we will visit together.


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