Hydrothermal explosion at Yellowstone National Park's Biscuit Basin damages part of boardwalk-InfoExpress

A hydrothermal explosion took place at Yellowstone National Park's Biscuit Basin in northwest Wyoming Tuesday morning, sending boiling water and steam into the air and causing some damage to a boardwalk, officials said.

The small, localized eruption occurred at 10:19 a.m. local time near the Sapphire Pool, which is about two miles northwest of the Old Faithful Geyser, the National Park Service said.

The basin, including the parking lot and boardwalks, is temporarily closed until park officials determine the area is safe.

No injuries were reported, and the extent of damage is still being assessed, the National Park Service said. Photos shared by Yellowstone on social media showed a boardwalk covered in debris, with a bench and portions of a fence destroyed.

"Hydrothermal explosions, being episodes of water suddenly flashing to steam, are notoriously hard to predict," the U.S. Geological Survey said on social media. The agency likened the eruptions to a pressure cooker, adding that "they may not give warning signs at all."

Park staff assess the damage to Biscuit Basin boardwalks after a hydrothermal explosion at Yellowstone National Park in Wyoming on July 23, 2024. National Park Service

Volcanoes, on the other hand, do emit warning signs, and there were no signs of an imminent volcanic eruption or seismic activity in the Yellowstone region after the explosion, the USGS said.

Park officials similarly said that volcanic activity remained "at normal background levels."

Hydrothermal explosions can be "violent and dramatic events resulting in the rapid ejection of boiling water, steam, mud and rock fragments," according to the USGS. Larger geysers can reach over a mile high and leave craters hundreds of feet wide.

"This sort of thing happens 1-2 times per year somewhere in Yellowstone (often in the backcountry, so it goes unnoticed)," the USGS said on social media. "It's an underappreciated hazard that we've been emphasizing for years. A similar event happened in roughly the same place in 2009."

The agency added that "small doesn't mean that it was not spectacular."

— Li Cohen contributed reporting.