A hydrothermal explosion in Yellowstone National Park in the Biscuit Basin thermal area on July 23, 2024. USGS Volcanoes / Facebook

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A hydrothermal explosion at Yellowstone National Park sent tourists fleeing for safety on Tuesday.

The event occurred in the morning at a group of hot springs called Biscuit Basin, just north of the popular Old Faithful Geyser.

Dozens of onlookers watched from a boardwalk as steam, water, dirt and rock erupted into the sky, reported The Guardian.

One of the spectators, a tourist named Vlada March, recorded the incident on her cellphone. March and her family were on a guided tour when the guide pointed to steam coming up from the ground, The New York Times reported.

“‘Oh look,’ he said. ‘This is unusual.’ I took out my phone like everyone does. Suddenly it became a huge, dark cloud full of rocks,” Vlada told The New York Times in a phone interview. “It was a huge cloud, it covered the sun. For a few moments, you couldn’t see the sun it was so dark.”

In the video, March can be heard imploring her children to run.

After the initial burst, people turned to watch as a large cloud of steam formed, reported The Guardian.

Biscuit Basin was closed for the safety of visitors after the falling rock damaged a walkway constructed to keep people from walking on dangerous and fragile geothermal formations. No injuries have been reported from the incident.

Visitors to Yellowstone are advised to stick to the trails and boardwalks in geothermal areas. Some of the springs and pools have a thin crust sitting atop the scalding hot and at times acidic water. Since 1890, at least 22 people have died from injuries caused by thermal features.

Following the explosion, park geologists are conducting an investigation of the area.

Mike Poland, a scientist with the Yellowstone Volcano Observatory, said the eruption could have been caused by a clogged passageway inside the natural network of ducts beneath the park’s geothermal features.

Poland said such a clog would have led to built up pressure and heat until the water became steam, expanding in volume and exploding.

According to Poland, Yellowstone is home to the biggest known crater created by a hydrothermal explosion on the planet, measuring 1.5 miles across.

“What we saw today was spectacular and definitely hazardous. But on the scale of what the Yellowstone system has done in the past, it was relatively small,” Poland said, as The Guardian reported. “It’s a very good reminder of an underappreciated hazard in Yellowstone.”

Yellowstone National Park sits on an enormous, dormant volcano. The United States Geological Survey (USGS) said the park’s volcanic system remains at normal levels.

According to the USGS, on average, large hydrothermal explosions happen every 700 years.

“Although large hydrothermal explosions are rare events on a human time scale, the potential for additional future events of the sort in Yellowstone National Park is not insignificant. Based on the occurrence of large hydrothermal explosion events over the past 16,000 years, an explosion large enough to create a 100-(meter)- (328-ft-) wide crater might be expected every few hundred years,” USGS added.

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