A video has appeared of terrified tourists screaming at a man who can be seen walking over the active geyser of the Yellowstone volcano in Wyoming, USA.
People shouted for the man to get back on the boardwalk and step away from the geyser.
Others gasped as he appeared to lower himself to the ground and take a peek inside the fuming geyser.
The shocking video was filmed and posted on Facebook by Ashley Lemanski on Saturday.
Ms Lemanski described the bizarre incident as a “rare occurrence at Old Faithful”.
The man was reportedly arrested by a park ranger after she walked away from the geyser and into the parking lot.
He was charged with violations, including being off-trail in the thermal area.
Yellowstone National Park is found in the northwest of the United States, spread across the corners of Wyoming, Idaho and Montana.
The first national park in the USA, the park is also known for its wildlife and geothermal features, especially Old Faithful geyser.
According to the United States Geological Survey (USGS), volcanoes are elevated to supervolcano status if they ever had an eruption of magnitude 8 on the Volcano Explosively Index (VEI).
Supervolcano eruptions of this size throw up vast amounts of volcanic material, measuring up to 250 cubic miles (one million cubic km).
Yellowstone has had at least three such cataclysmic eruptions in the past, several thousand times stronger than the 1980 eruption of Mount St Helens.
The Yellowstone supervolcano last erupted 2.1 million years ago, 1.2 million years ago and about 640,000 years ago.
Since that last “caldera-forming” super-eruption 640,000 year ago, the USGS has recorded at least 80 nonexplosive events.
The USGS said: “Of these eruptions, at least 27 where rhyolite lava flows in the caldera, 13 were rhyolite lava flows outside the caldera and 40 were basalt vents outside the caldera.
“Some of the eruptions were approximately the size of the devastating 1991 Pinatubo eruption in the Philippines, and several were much larger.
“The most recent volcanic eruption at Yellowstone, a lava flow on the Pitchstone Plateau, occurred 70,000 years ago.”