If the volcanic eruption doesn’t scare you, the mudflow should

Studying tree rings helped scientists pinpoint when Mount Rainier last sent a lahar down its steep slopes, which could help planners anticipate future mudflows.

An outpouring of magma isn’t the biggest risk to people downhill from Mount Rainier in Washington. The active volcano’s greatest danger comes from lahars — amalgams of mud, rock and water that are as dense as wet concrete.

Over the past several thousand years at least nine large lahars have barreled down the steep slopes of the 14,410-foot mountain, sometimes reaching as far as the Puget Sound some 60 miles away. The largest lahar of the past 1,000 years was known as the Electron Mudflow, named for the small hamlet of Electron.

That event buried the nearby landscape in nearly 20 feet of mud. But scientists have struggled to precisely date when this event occurred. Knowing the year could make it possible to correlate the lahar with other events and therefore better predict future muddy outbursts.

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