One of the most dangerous volcanic hazards in the Cascades is lahars

Lefty Graves
Lahars from Mount St. Helens carried this large boulder downstream as it ripped down trees and left a thick mudflow deposit in May of 1980Photo

Lahars are considered one of the most perilous volcanic hazards in the Cascades region. Lahars is an Indonesian word that describes the mudflow or debris field originating from the slopes of volcanoes. Lahar's debris fields may carry a slurry of pyroclastic materials such as rocks, mud, water, and other debris in the flow field. They happen when the ground becomes too soggy because of rain or snow melt, and the ensuing result is a landslide. Smaller debris fields are very common in the Cascade Mountain Range of Washington State, where they are formed when heavy rains and rapid snow melt cause shallow landslides.

Such debris fields will destroy everything in their path. This occurred recently when Mt. St. Helen’s stranded 12 people on her peak for an unplanned overnight stay. A landslide closed the road leading up to the observatory, and 12 visitors were treated to a helicopter ride in the morning to get back to civilization. Their cars, on the other hand, may be stranded there for quite some time.

Washington State is home to five volcanoes, all susceptible to lahars. The volcanoes of the Cascades have a lot of debris from former eruptions that make them more susceptible to the sudden landslides that happen when the snow melts, and heavy rains ensue.

Towns and other areas located downstream from such dangers are in serious jeopardy should lahars or eruptions occur. Approximately 5000 years ago, Mt. Rainier erupted, resulting in an Electron Mud Flow. The lahar traveled down to the Puyallup River Valley. It was noted in 2009 by the USGS that as many as 78,000 residents could be in the danger zone should another eruption occur.

To further understand the risk factors, scientists have observed and must quantify what happens in such cataclysmic events. They’ve performed many experiments to see how quickly such lahars might reach towns in the region.

Residents of the Pacific Northwest must be aware of the potential for such dangers. Residents in the region should be aware and prepared to evacuate should such an event occur. Such events have taken place in the past, and the region is still at risk due to the volcanoes in the area. While the volcanoes are currently dormant, they may awaken at any time, just as Mt. St. Helen’s chose to do.

Having a plan and knowing the best time to evacuate is important. It’s also important to teach the children in the area the potential safety hazards and have plans in place to ensure their safety should they be away at school while their parents are away at work. While the public is encouraged not to live in fear, they are also encouraged to be aware of their surroundings and what is happening in nature.

© Lefty Graves. 2023 All Rights Reserved.

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Lefty has been writing online since 2000 on various topics, including youth mentoring, addiction recovery, parenting, gardening, advocating for seniors, sustainability, farming, and an eclectic mix of other topics. She writes about all things Washington. She resides on a farm with her family in Northeastern Washington State.

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