In 1869, Yellowstone was just a rumor to European Americans, believed to be a myth spread by hallucinating mountain men. When Charles Cook — of the Folsom–Cook–Petersen Expedition — wrote a seven-page article for Lippincott’s Magazine about “where Hell Rises,” his editors responded: “Thank you you, but we don’t print novels.”

In the years that followed, Yellowstone shed its mythical hell and became the world’s first national park. But the park still bubbles, flows, steams and seethes like no other place on Earth. And look no further than the rainbow-colored void known as Grand Prismatic Spring.

This 160-foot-deep hot spring is located in “Death Valley” or “Wonderland,” depending on how close you are to the steam. But how on earth did this place that was once believed to be the entrance to Hell become like this? This rainbow death trap has very little to do with hell — but you’d best still pay attention to the boardwalk.

Located in Yellowstone’s Midway Geyser Basin – just north of Old Faithful – Grand Prismatic is the largest, most colorful spring in the park. “With a circumference of 300 yards, it resembles a lake more than a stream,” wrote naturalist John Muir. One of the countless fountains in Yellowstone is enough in itself for a trip across the continent.”

This non-lake hot spring – the third largest in the world – has an average temperature of 160°F. But why does it come in so many colors? Mats of thermophilic microorganisms (single-celled, bacteria-like organisms) cling to the edges, with different species congregating at different temperatures and forming the outer rainbow of spring colors. It’s too hot for these little guys towards the center, leading to the dark, sterile blue tone found there. In warmer seasons, the water is surrounded by bright oranges and greens; In winter, its color dulls a bit, turning browner in tone.

And while the colors of the Grand Prismatic seem completely unique, “Many other hot springs and thermal pools have or had similarly beautiful colors,” said Shaul Hurwitz, Survey Hydrologist Geology of the United States, explained. “A prime example is Morning Glory Lake in Yellowstone’s Upper Geyser Basin, previously known as one of the most spectacular. But because people continuously throw coins and other trash into the pool, the water temperature changes, leading to different microbial populations and different colors.”

“Grand Prismatic is unique because of the way the light is dispersed,” notes Hurwitz. “For example, many other streams are surrounded by trees or cliffs, so the sun’s rays are dispersed differently.” As long as humans do not interfere with it, the Grand Prismatic’s colors will persist.

The ground where Grand Prismatic Spring sits is quite flat – which is why the stream has formed orange octopus-like tendrils, with silica-rich water flowing out in all directions. But look at a map and you’ll see mountain ranges on nearly every side of the park. Yellowstone is located in a convenient, lower clearing.

Why? The Yellowstone supervolcano “ate” the mountains about 640,000 years ago. The Lava Creek eruption sent ash as far as Des Moines and New Orleans, forming the Yellowstone caldera we know today. And then, of course, the glaciers rush by and leave “till” everywhere in their smooth path — even under the Grand Prismatic.

Through all of this, Yellowstone remains an active supervolcano, capable of causing another such explosion. A giant plume of magma – resembling an oblong ball of lava – now lies beneath the park, curling above the ground as it inhales and falling as it exhales. Previous explosions occurred 1.3 and 2.1 million years ago, meaning eruptions occur approximately every 650,000 years. Let’s do the math on that.

Note: While the magma flow remains stagnant, North America is heading southwest. About 16.1 million years ago, “Yellowstone” was present in Nevada. (You probably won’t buy real estate in Billings, Montana in a million years.)

A busy footpath runs along the north edge of the stream, on the Excelsior Geyser side, in Yellowstone’s Midway Basin. But for the best vantage point, climb the ridge south of the spring, up the trail to the Grand Prismatic Spring Overlook. It’s the closest thing you can get to shooting with a drone, and it quickly reaches 0.6 miles at 105 feet.

But Hurwitz notes that while the colors are 100% real, you may need to be patient. “Most people standing near the stream expected to see what they saw in the photo. These photos were taken in favorable lighting conditions; Additionally, depending on wind direction, water vapor above the lake can hide the beautiful colors.”

How not to discover it? By hopping on — or even stepping off the boardwalk. This is not a large natural hot tub.

“I tell people who will be joining me in this fieldwork, that what looks like a perfectly safe place to enter could, in fact, hide a large quantity of boiling water underneath and could give way as soon as you put weight on it.”

Oh, and if you can get out, your death is not from infection. “You will die of dehydration 2-3 days later, the skin is cooked and can no longer regulate water retention.” In other words: The NPS principle is there for a reason. Please obey them.