Expert baffled by ferocity, distance of ‘freakish’ slide

[uppityperson]

Animation of slide at link. "This computer animation from the U.S. Geological Survey shows how the Oso landslide roared off the slope and engulfed the neighborhood and Highway 530. Scientists estimate the slide was traveling 60 mph and crossed the valley in one minute. This animation is about 12 times faster than real time. The scale indicates the depth of the slide. Darker blue equals thicker deposits."

http://seattletimes.com/html/localnews/2023331700_mudslidescientistxml.html

Geologists were stunned at how far and how fast the Oso slide ran out — one expert estimated the slide hit the Stillaguamish River at 60 mph. But scientists also hope that detailed analysis will help prevent such tragedies in the future.

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“It was a freakish thing,” said Iverson, of the U.S. Geological Survey’s Cascades Volcano Observatory. “I’m not sure anybody would have anticipated a slope like that would liquefy the way it did.”

Using a new computer model, Iverson estimated that the mass of mud, rocks and trees was traveling about 60 mph when it slammed into the river. Imagine standing on the side of a freeway when a semi truck barrels past at 60 mph, Iverson said. Then imagine a battalion of eighteen-wheelers, half a mile wide, headed straight at you....

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The hope is that by understanding what caused the slide to morph into a monster, scientists will be able to better identify the most dangerous hazard zones in the future, said Jonathan Godt, a Denver-based USGS expert who also visited the Oso slide.(more)

[Sunlei]

1. The entire valley sides have scallop shapes above it from past slides. Silt deposits when there used

to be a glacier? and then Stillaguamish was a raging river that filled the entire 'valley'. Or perhaps even past tsunami silt.


'A legend from the Stillaguamish people.'
One time, long ago, the waters in the whulge came up high, and flooded all the country way up into the mountains. First a big black Thunderbird flew over the country and made much noise, then it beget to rain. It rained and rained. The water came up and up, and when it stopped there were only some high hills and mountains sticking out. After a ‘long time it went down again. You can see sometimes now clamshells high up in the hills, and some places up in the mountains white logs lying just like on the beach. They were left there by the water.