Layers: Mt. Rainier, Seattle, Tacoma

LAYERSRainierDetailOneHer white mantled majesty looms placidly over the entire Seattle-

Tacoma metroplex.  Reassuringly there anytime the sky is clear enough to reveal her beauty.  Her permanence is somehow reassuring despite the fact that Mount Rainier is the volcano in the backyard.  One day, sooner or later, this mountain that looks so permanent and stable will erupt with booming explosions spewing forth blankets of hot ash and torrents of steaming mud.  A Mount Saint Helens on a fearfully grander scale; millions of people, their lives and livelihoods will be at immense risk.

The volcano is the melt off by-product of the modest sized Juan de Fuca plate, which is slowly, fitfully grinding down beneath the North American continent.  The relative motions and dissimilar densities of these large plate slabs of oceanic and continental crustal rock dictate this downward motion.  The descent will not be gentle. The frictional heat generated will melt the minerals that make up the rocks sending plumes of heat toward rocks nearer the surface that are more easily melted.  Large mountain-sized masses of rock will melt in place and slowly rise, hot air balloon-like to the surface. Water will tend to dissolve in the mass leading to further melting as it interacts with the rock above.  This water vapor gas charged magma remains ready to explode upward and outward should additional magma push in from below and when cracks in the surface or a decrease in overlying containing pressures allow an unstoppable expansion. The eruption will be Plinean, rapid, extensive and murderously effective in extinguishing all life within many miles. The flanks of the mountain, the National Park facilities and the communities at the base will be smothered by pyroclastic flows of fearsome proportions.  Vesuvius-like incandescent rock and ash will sear and bury everyone and everything in their path.  Pompeii revisited.  Further from the mountain, day will turn to night as the now cooled ash spreads and disperses.  It is likely that the ash cloud and billows of steam from the melting snow and glacial ice will obscure the birth of the real terror for those who on a clear day could see Mount Rainier.  The ash, broken rocks and lava will mix with the melt water and plunge down every side of the mountain’s radial drainage pattern into the scores of stream valleys below. The viscous steaming mud flow will advance at hundreds of miles an hour. The lahar will expand and extend, enveloping the valleys surrounding the mountain and all in its path, reaching Tacoma and perhaps even parts of Seattle.  It will still be hot enough to send up clouds of steam as it plunges into Puget Sound.  While modern monitoring and evacuation plans should give warning and time to escape they have yet to be tested.  Hundreds will probably die gruesome deaths and the economic geography of the region will be destroyed….

(From Mt. Rainier, Seattle, Tacoma)

Text prepared by Dr. James Brey

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Layers: Places in Peril

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