"Vancouver, Vancouver, this is it!"

Twenty-five years ago today.

In March 1980, Mount St. Helens began to stir. Authorities closed off a "red zone" around the mountain and restricted access as small puffs of ash emerged from newly formed craters on the mountain's summit. The volcano was stirring.

At 8:32 AM Pacific, May 18, 1980, a magnitude 5.1 earthquake dislodged the hardened magma plug that had trapped the violent pressures below. On a ridge to the northwest, a geologist named David Johnson saw the movement and called the volcano observatory in Vancouver, Washington: "Vancouver, Vancouver, this it!" As the plug fell away to the north, the suddenly released magma and gases rushed out in a superheated cloud of ash and poisonous gas, incinerating everything in their path and rearranging the landscape in an explosion that could be heard as far away as Canada. The hot cloud moved north at incredible speeds, blasting down trees 17 miles from the mountain. With the plug gone, an ash plume tens of thousands of feet high rose into the blue Washington sky, carried east by the prevailing winds.



East of the mountain, the ash clouds rained pumice and a haze of ash decended on Eastern Washington. In Yakima, ashfall was measured in inches.

On the mountain itself, the hot ash and rock melted the mountain's snows and glaciers, and the rushing waters absorbed finely pulverized rock to form giant mudflows that moved down the nearby rivers, crushing homes and bridges and scouring the floodplain. Flowing down the Toutle river, one mud flow almost destroyed the Interstate 5 bridges and filled in the Columbia River channel, raising its depth from forty to less than thirteen feet deep, stranding several ships in Portland.

David Johnson and 56 others died that day, victims of a force of nature Americans had little previous experience with. That would change.

The Cascades are lined with several similar resting volcanoes, from Mount Baker in the north to Mount Lassen and Mammoth Mountain in California. Now science is attempting to learn all it can, so at least we will have a better warning and a better understanding of the forces around us. We have already learned much in unexpected areas - such as how forests grow, and how nature responds to disaster. And we are learning to plan and prepare, as much of the human reaction in 1980 was ad hoc and improvised.

As for Mt. St. Helens herself, she has recently reawakened. A large mound has been growing next to the one she built after the 1980 eruption, which ceased growing in 1986. Volcanologists are watching, and waiting. What happens next is anyone's guess.


Links:
Mt. St. Helens Volcanic National Monument
USGS - Mount St. Helens
Seattle PI
SF Chronicle