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Living with volcanoes

While the Pacific Northwest takes stock of the devastation, and wonders what to do with all that volcanic dust, there is an important lesson to be heeded in the Mt. St. Helens eruptions. Awesome as they are, such outbursts in that region now are known to be expectable natural events. Part of the rehabilitation effort should be area-wide contingency planning for living in a live volcanic region.

It is understandable that little thought was given to this as the region developed. Until recently, geologists had only a vague notion of the underlying causes of the volcanism that helped produce such a scenic landscape. There was little to challenge the complacent notion that such causes were deeply dormant, if not extinct.

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But over the past two decades, the insights of the new theory of plate tectonics have shown those causes to be alive and very active. Earth's outer layer is broken into 10 or so large plates. Most of the world's earthquake activity and volcanism occur along the margins where plates interact.

Along the US West Coast, two such plates now are sliding past each other. Formerly, one plate was plunging beneath another. This past and present plate activity has shaped the landscape, gives rise to earthquakes, and makes dormant volcanoes such as those of the Cascade Range a continuing threat which must be respected in the region's development.

It is worth recalling the warning given a few years ago in the book "Earth," by Raymond Siever of Harvard University and presidential science adviser Frank Press. Referring specifically to the type of situation represented by the Pacific Northwest, they wrote: "Although it will be difficult, it may soon be possible to predict future eruptions of known active or temporarily dormant volcanoes. But what of the long-extinct volcanoes? Will they come to life suddenly -- as Vesuvius did? Some currently inactive, but potentially dangerous volcanoes are Mt. Baker and Mt. St. Helensm in Washington, Mt. Hood in Oregon, and Mt. Shasta in California."

As with other natural hazards -- such as earthquakes, tornadoes, or hurricanes -- the advance of scientific knowledge makes it possible to minimize the danger to human life and to make potential property damage a known risk which can be assumed or avoided as seems sensible in specific situations.

Zoning can prevent unwise development of high risk areas. Drs. Press and Siever note, for example, that it should be possible to identify areas vulnerable to volcano-caused floods -- such as that which has threatened communities downstream of Spirit Lake. In such places, they add, "it seems better to prevent habitation." In less vulnerable, but still potentially hazardous, locations, stand-by evacuation plans could be developed so that people would know what to do if early warning signs of a possible eruption were detected.

Some news reports have been calling the Mt. St. Helens eruption a once-in-a-millennium event. That is a mistaken perspective which should not obscure the clear warning of the need for preparedness.

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