Surprise Blast of Rock, Water, and Steam in Yellowstone Sends Dozens Running for Safety

CHEYENNE, Wyo.—A surprise eruption in Yellowstone National Park shot steam, water, and dark-colored rock and dirt high into the sky Tuesday and sent sightseers running for safety. The hydrothermal explosion happened around 10 a.m. in Biscuit Basin, a collection of hot springs a couple of miles north of the famous Old Faithful Geyser. A video posted online showed a couple of dozen people watching from a boardwalk as the eruption sprayed and grew in front of them. As water and debris began to fall, they ran to keep clear, some yelling “Back up!” and “Holy cow!” People then turned to watch the spectacle under a huge cloud of steam....