Thoughtless Yellowstone tourists stroll right onto Grand Prismatic for photos

Grand Prismatic spring, Yellowstone National Park, USA
(Image credit: Getty Images)

A pair of tourists decided they wanted a closer look at Yellowstone National Park's biggest and most famous hot spring, wandering off the boardwalk and ignoring warning signs to stand right on the colorful bacterial mats at Grand Prismatic. 

A video of the incident (which you can see below) was shared via infamous Instagram account TouronsOfYellowstone this week. It shows the pair standing right at the water's edge, despite warnings from the National Park Service (NPS) that the ground around springs can be very thin, with scalding hot groundwater just below the surface. People have been seriously injured after accidentally slipping in.

"Hot springs have injured or killed more people in Yellowstone than any other natural feature," says the NPS. "Keep your children close and don’t let them run."

Note that the video has a caption referring to Idaho, despite Yellowstone being in Wyoming.

The NPS takes trespassing in thermal areas very seriously. Earlier this month, actor Pierce Brosnan pleaded guilty to straying off the boardwalk near Mammoth Terraces, and was ordered to pay fines totalling $1,500. Brosnan claimed that he missed signs warning visitors to stick to established trails.

"I deeply regret my transgression and offer my heartfelt apologies to all for trespassing in this sensitive area," he wrote on Instagram. "Yellowstone and all our National Parks are to be cared for and preserved for all to enjoy."

Wandering off-trail at Grand Prismatic also risks damaging the delicate bacterial mats that give the spring its signature vivid colors. Different types of thermophilic (heat-loving) bacteria thrive at different temperatures, and their relative concentration of chlorophyll and carotenoids give them their different hues.

"Imagine living in near-boiling temperatures, in hydrothermal features with the alkalinity of baking soda, or in water so acidic that it can burn holes in clothing," says the NPS. "Microorganisms in Yellowstone need these extremes to survive."

Cat Ellis

Cat is the editor of Advnture, She’s been a journalist for 15 years, and was fitness and wellbeing editor on TechRadar before joining the Advnture team in 2022. She’s a UK Athletics qualified run leader, and in her spare time enjoys nothing more than lacing up her shoes and hitting the roads and trails (the muddier, the better), usually wearing at least two sports watches.