By Pat Jenkins The Dispatch Mount Rainier at its worst, and lessons learned from a volcano-devastated town in South America, will be the subject of a public meeting involving federal and local officials next Wednesday in Ashford. Carolyn Driedger of the U.S. Geological Survey's Cascade Volcano Observatory and Scott Beason, a Mount Rainier National Park geologist, will discuss what they learned from their visit to Colombia for a study of the effects of a volcanic eruption, and how that 1985 event can help protect areas around Mount Rainier in the event that slumbering volcano awakens. The presentation, accompanied by a free chili dinner, is scheduled for 6 to 8 p.m. at Columbia Crest STEM School. In addition to Driedger and Beason, presenters will include Fire District 23 chief Garry Olson, who will share evacuation and emergency communication plans for the Nisqually River valley and other surrounding communities. Pierce County Emergency Management officials will provide information that families and residents can use to make their own preparedness plans. Colombia suffered one of the worst volcanic disasters of the 20th century nearly 30 years ago when Nevado del Ruiz erupted. Lahars - flows of mud and water - from the ice-clad mountain destroyed surrounding communities and killed more than 23,000 people. The disaster made a lasting impact worldwide on scientific studies of volcanos and disaster preparations and management. Lahars, which can be touched off by an eruption of lava or hot gasses that melt a glacier, or by avalanches and earthquakes, can push mud and debris at a high speed. The flow has the consistency of wet concrete. Mount Rainier has produced major lahars every 500 to 1,000 years and smaller flows more frequently. The most recent big lahar to reach the Puget Sound region's lowlands was what historians call the Electron mudflow, which happened about 600 years ago. The flow was more than 100 feet thick in the area now known as Electron and about 20 feet thick in what today is Orting. A report in mid-2012 from the state Department of Natural Resources estimated that a a lahar spewing from the mountain could cause property damage and losses of up to $6 billion to communities in the Puyallup Valley portion alone of Pierce County. Due to the weakened rocks on the upper west flank of the mountain, the Puyallup Valley is the area considered most susceptible to lahars. Lahar-related flooding has the potential to reach Commencement Bay in Tacoma. Ten other river valleys are considered hazard zones for lahars, lava flows and pyroclastic flows in the event of a major eruption. The valley drainages include the Nisqually River, with Alder Lake and the Elbe area along the way and Eatonville nearby, and GÇô in Lewis County to the south GÇô the Cowlitz River and Riffe Lake. All the areas could be "inundated" if eruptive events were similar to those in the past, the DNR report states. The report also notes that the hazard from lahars isn't equal in all the valleys. Experts say at least 60 lahars from Mount Rainier have traveled as far as 70 miles downstream.
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