MYNORTHWEST NEWS

Washington’s scorching weather causes lahar on Mt. Rainier

Aug 17, 2023, 1:02 PM

lahar mt rainier volcano...

A small registered lahar off of Mt. Rainier (Photo courtesy of USGS Volcanoes)

(Photo courtesy of USGS Volcanoes)

Washington’s intense bout with record-breaking temperatures likely triggered a glacial mudslide on Mount Rainer.

Monitors registered the lahar Tuesday afternoon, saying it lasted for hours.

What are lahars?

Lahars, “along with debris flows and debris avalanches, are masses of rock, mud and water that travel rapidly downslope and downstream under the action of gravity,” the Cascades Volcano Observatory via the U.S. Geological Survey (USGS) says.

“Volcanoes are a perfect setting for these events because of an abundance of steep, rocky rubble and a ready source of water in the form of rain, snow or ice, the observatory added. “Lahars can flow many miles downstream from the volcano, making this the most threatening hazard in the Cascades.”

More on Mount Rainier: Missing climber’s body found in crevasse; he was celebrating 80th birthday

Federal geologists believe the South Tahoma glacier released a burst of water, starting a slide that ran under the Tahoma Creek Bridge on Nisqually-Paradise road. The lahar’s path is still visible on the Southwest side of Rainier. This lahar is considered “small.”

Lahars can occur by rapid melting of snow and ice during eruptions, by liquefaction of large landslides (also known as debris avalanches), by breakout floods from crater lakes, and by erosion of fresh volcanic ash deposits during heavy rains, the observatory notes.

More on volcanic eruptions: Swarm of quakes at Alaska volcano could mean eruption coming

Potential community effects of lahars

Lahars and excess sediment can cause serious economic and environmental damage to river valleys and flood plains, according to the USGS. Large lahars can crush, abrade, bury, and carry away almost anything in their paths. Buildings and valuable land could be partially or completely buried. USGS described large lahars as “rivers of concrete.”

Lahars and pyroclastic density currents (or flows) have been responsible for almost 40% of all fatalities related to volcanoes, according to Forbes.

A fire ban for Mount Rainier National Park will also be in place starting Friday, barring all campfires and the use of fire pits or barbecue grills. Portable stoves and lanterns that can use bottled fuel and be turned off are still allowed.

The ban comes as much of Western Washington is dealing with various levels of drought, making the region more susceptible to wildfires.

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Washington’s scorching weather causes lahar on Mt. Rainier