Water burst from the business end of a glacier on Mount Rainier earlier this week, creating new waterfalls and tumbling boulders downstream. The resulting damage closed a road and trail in the national park.
The event on the South Tahoma Glacier occurred Monday between 6:48 and 7:58 p.m. without warning, according to a news release from Mount Rainier National Park on Thursday.
No one apparently was injured by the flow.
Flows the color of watery concrete damaged and temporarily closed the park’s Westside Road and Tahoma Creek Trail.
The glacier, located on the mountain’s southwest side, feeds into the Nisqually River.
Geologists said similar events could occur in the coming weeks or months.
Park staff realized something had happened on Tuesday morning when they noticed Tahoma Creek had turned “sediment-rich.”
Aerial reconnaissance confirmed the source and outflow areas. Video shows a series of large waterfalls exiting the glacier, one from a new cavern.
The event was so powerful it was recorded on seismic equipment, the Pacific Northwest Seismic Network reported on Friday.
Glacial outburst floods and debris flows are not uncommon on the mountain, the park said, but exactly how and why they occur is a mystery.
“Although the mechanism remains unknown, geologists report that stagnant water and slow moving ice on the lower part of a glacier combined with faster moving ice on the upper glacier has been associated with such events,” the park said.
The Tahoma Creek valley has seen at least 32 outburst floods since 1967.
The park advised visitors to keep watch for unusual sounds, shaking ground and changes in water levels of creeks and rivers and if observed, head to higher ground.