A hydrothermal explosion rocked part of Biscuit Basin in Yellowstone National Park on Tuesday, damaging a boardwalk and sending several park guests fleeing for safety.
The explosion occurred in the Biscuit Basin thermal area at about 10 a.m. local time and appeared to have originated near Black Diamond Pond, according to the U.S. Geological Survey. There were no immediate reports of injuries.
The USGS said Biscuit Pool, boardwalks and parking lots are closed for visitor safety while park geologists investigate what happened.
This popular tourist spot is located about two miles northwest of Old Faithful. Volcanic activity in the Yellowstone area remains at normal levels, according to the U.S. Geological Survey.
What are hydrothermal eruptions?
Hydrothermal eruptions occur when hot water in a volcanic system turns to steam in a confined area, Lisa Morgan, a research geologist emeritus with the U.S. Geological Survey, wrote for Yellowstone Caldera Chronicles, a publication of the Yellowstone Volcano Observatory.
“Blowouts are one of the most significant and least visible geological hazards,” Morgan said. Sudden drops in pressure cause a rapid expansion of superheated fluids or vapors, triggering an eruption that creates craters.
Yellowstone is the epicenter of geological hazards worldwide, and eruptions occur several times a year, Michael Poland, the scientist in charge of the observatory, told USA Today.
The area northeast of Yellowstone Lake is home to the three largest known hydrothermal craters on Earth. The largest is Mary Bay, a 13,000-year-old crater, measuring a mile and a half across; Turbid Lake is a mile across and formed 9,400 years ago; and Elliot Crater is nearly a half-mile across and formed 8,000 years ago.
An explosion large enough to leave a crater the size of a football field is expected to occur every few hundred years, according to the observatory.
According to Poland, eruptions can occur anywhere there is hydrothermal activity. Other potential hotspots include New Zealand, Iceland and Chile.