An underground hydrothermal explosion at Yellowstone National Park sent visitors running for their lives Tuesday morning as a massive black mushroom cloud of steam and debris rose hundreds of feet in the air.
The eruption was in the national park’s Biscuit Basin area, originating near Black Diamond Pool, located about 2.1 miles northwest of Old Faithful.
Frightening footage shows about a dozen tourists fleeing along the boardwalk leading up to the thermal pools, some screaming as large chunks of rock spewed in all directions.
Miraculously, no one was injured in the explosion, according to the United States Geological Survey (USGS), but Biscuit Basin, as well as its parking lot and boardwalks, have been temporarily closed for visitor safety.
According to the USGS, such explosions occur “when water suddenly flashes to steam underground,” saying such events are “relatively common in Yellowstone.”
The federal agency says the explosion is not an indication of volcanic activity and that it wasn’t caused by magma rising towards the surface.
Video taken after the massive plume subsided shows the boardwalk littered with debris as tourists carefully make their way to check out the steaming underground cauldron.
Similar explosions are not unheard of. Porkchop Geyser in Norris Geyser Basin experienced a blow-up of its own in 1989, and experts recorded a similar, though smaller, event at the same basin in April of this year.
According to USGS, Yellowstone is home to the “largest and most diverse collection of natural thermal features in the world.”
The explosion is under investigation by Yellowstone geologists.