A vibrant, steamy view of the Grand Prismatic Spring in Yellowstone National Park, captured in the height of summer, in Wyoming on April 23, 2025. (Getty Images)

Some of the prime attractions that make Yellowstone National Park stunning and unique are the park's 10,000-plus hydrothermal features - geysers, mud pots, cauldrons, steam vents and hot springs. But every year, visitors ignore posted warnings and common sense at these mesmerizing sites.

Already this summer, several park visitors have been caught disregarding federal regulations put in place to both protect people and preserve the tiny organisms living in and around hot water.

The first known thermal injury of the year happened on July 28, when a teenager walked off-trail at the Lone Star Geyser near the Old Faithful Geyser and burned his foot and ankle. The 17-year-old had been walking on a thin, delicate crust that broke under his weight, plunging his lower leg into scalding water. According to a park news release, emergency medical staff responded to the scene and transported him to a hospital for treatment.

The Lone Star Geyser puts on quite a performance as it erupts for more than 15 minutes at Yellowstone National Park in Wyoming on Dec. 17, 2018. (Getty Images/iStockphoto)

On the same day, less than 10 miles away, another man reportedly walked across a thermal area near the colorful Grand Prismatic Spring. In photos posted by another visitor on Facebook, the man seems to be wearing flip-flops. The photos appear in a group called "Yellowstone National Park: Invasion of The Idiots!" which chronicles poor behavior in the park, from approaching bison to trespassing in closed areas. The user who posted photos of the incident wrote that the man was "repeatedly walking all over the bacterial mats near Grand Prismatic gathering hats that had flown off of other visitors' heads."

SFGATE brought the video to the attention of spokesperson Linda Veress, who sent the link to rangers for investigation. "We were not aware of this video or incident," she said.

A video posted on Instagram to "Tourons of Yellowstone," another page chronicling bad behavior, seems to show a middle-aged man drinking from a hot spring in July. A still photo shows him kneeling on the side of the boardwalk, appearing to fill a plastic cup with water. And it's not just humans who sometimes get too close to hot springs. A bison died in June after slipping into scalding water at Grand Prismatic Spring.

Bison ride through columns of steam at Yellowstone National Park's Grand Prismatic Spring in Wyoming. (REDA/Universal Images Group/Getty Images)

Yellowstone warns visitors to stay on boardwalks and designated trails in thermal areas. The pathways "protect you and delicate thermal formations," according to the park's website. The high water temperatures are dangerous: More than 20 people have died from burns after entering or falling into Yellowstone's hot springs. Drinking the water also isn't safe: In addition to hot temperatures, water from the hot springs can contain harmful doses of chemicals, such as arsenic and mercury, or even brain-eating amoebas.

"Hot springs also contain algae, bacteria, and fungi found nowhere else in the world; coming in contact with these life forms can destroy them," according to the park's website. "Resist the temptation to touch!" Microorganisms living in hot springs and other thermal features are called extremophiles because they survive in conditions that are too extreme for human life, such as water that's near boiling and/or acidic to the extent that it can burn a hole through clothing.

Touching thermal features or runoff, as well as swimming or soaking in hot springs, is strictly prohibited. So is throwing objects into the pools.

It can be hard to catch an offender if law enforcement isn't already nearby or if other visitors can't connect the person to their car's license plate. But some thermal trespassers occasionally do face punishment.

In 2024, a Washington man went to jail for a week and received a 2-year park ban for walking off the boardwalk near a geyser. Actor Pierce Brosnan was fined $1,500 for walking on a closed thermal area in Yellowstone in 2023, and two men were sentenced to 10 days in jail, as well as receiving a 5-year park ban and being ordered to pay $540 in fines, after trespassing near Old Faithful in 2019.

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