Turns out the biggest dangers at Yellowstone National Park may be tourists themselves. Besides not staying in designated areas, they also tend to leave behind a number of litter.
In particular, Yellowstone tourists tend to leave behind their hats. So far, workers have found over 300 hats in thermal areas.
"When recreating or working in Yellowstone National Park, it's not uncommon to stumble across a team of National Park Service geologists in distinctive red safety vests. These folks are part of Yellowstone's Geology Program: a specially trained team dedicated to protecting, remediating, and studying Yellowstone's incredible geology and hydrothermal features," Margery Price, a physical science technician at the Yellowstone National Park Geology Program, wrote in a weekly Yellowstone Caldera Chronicle story.
Yellowstone Caps
Employees frequently clean up the national park to maintain the wilderness of the park. But it's not an easy task, requiring tools and creativity to retrieve some of this letter.
Price explained, "One of the Geology team's most important tasks is hydrothermal area cleanup. Yellowstone's picturesque landscapes are visited by over four million visitors each year. This immense amount of visitor traffic combines with the area's intense winds to create a near-constant stream of trash and hats that blow into delicate hydrothermal areas. Nearly all of this litter is unintentional, although sunflower seed shells, orange peels, and other food materials discarded by the occasional visitor accumulate as well and are particularly time-consuming for the team to remove."
In 2025 alone, the Yellowstone Geology crew collected more than 13,000 pieces of trash and over 300 hats from the thermal areas. That's a startling $6,000 in caps. Keep them on your head.
Price continued, "With so much time spent collecting debris, it's only natural to find some bizarre items. Favorite finds from the team during the summer of 2025 include a Birkenstock sandal, a pizza box with slices still inside, a fake Louis Vuitton bucket hat, a stuffed koala toy, a ball cap with the phrase "I PEE IN THE LAKE," and a Polaroid picture of Excelsior Geyser—which was found within Excelsior Geyser's crater!"
