Yellowstone National Park had a steamboat geyser eruption on Friday, for the first time in eight years.
The blast, lasting nine minutes, sent steaming hot water an estimated 200 to 300 feet in the air, according to the Salt Lake Tribune, citing park geologist Hank Heasler.
No one knows when the geyser will explode next.
It’s gone as long as 50 years without a major, while in 1964 it erupted a record 29 times.
Steamboat is the biggest geyser at the park, out of 500.
The eruption at 7:30 p.m. on July 31 drew onlookers.
“It was an amazing experience. This thing sounded like a locomotive,” Robb Long, a freelance photographer from Sioux Falls, S.D., said. “Everybody was frantic, taking pictures. People were running down there trying to get to it before it went away, and park rangers were running around trying to gather up people so they didn’t get too close.”