14 Shake and Bake

In 2010, two faculty, students, and I climbed Mt. St. Helens in Washington state. Mt. St. Helens is the most active of the volcanoes in the Cascade Mountains, and it still showed the scars from its last major eruption in 1980. That eruption is considered the most disastrous in U.S. history, blowing 1,300 feet off its height, destroying 200 homes, and killing 57 people. And the loss of life would have been much worse if not for the work of the U.S. Geological Survey in evacuating the area in advance of the blast.

THe U.S.G.S. was monitoring Mt. St. Helens for activity (video), watching for an increase in earthquake frequency and gas emissions. In addition,a bulge had started to form on the northern flank of the volcano. It was this bulge that U.S.G.S scientist David Johnston was monitoring on May 18th, 1980, when a landslide set off a lateral blast that travelled at over 300m.p.h. directly toward him. His body was never found. The Cascades Volcano Observatory is now named for him.

In the 30 years since that huge eruption, a glacier accumulated in the cone, reaching as much as 600 feet thick. Trees had grown back, having all been flattened in the blast. The night before our climb, we camped at Climbers Bivouac at 3,700 feet elevation. The hike up the next morning rose 4,500 feet over a 5-mile distance. Tough, but doable. The toughest part was the poor traction in the glacial snow, thick near the top despite our climb being in late July. The alternative, climbing through the boulders separating the glaciers, was little better. However, the view from on top was worth it—Mt. Baker, Mt. Jefferson, and other Cascade volcanoes each way we looked.

On the way down, several us decided to slide in the snow, not a particularly bright idea. We were lucky no one slammed into a boulder. I snapped a trekking pole trying to slow down. At least one group member got her pants packed full of snow.

Notes on Earthquakes and Volcanes:

Earthquakes are difficult to predict in the short-term. For a geologist to say, “There is a 85% chance of a major earthquake in this area in the next 70 years,” is really quite an accomplishment. But the politician that wants to get elected again in two years usually isn’t looking 70 years into the future. But looking ahead is the main thing we can do to reduce the costs of earthquakes. By planning and building well, we can save lives:

Zoning laws can be used to control the type of structures built in an earthquake zone—no nuclear reactors allowed!

Building codes are established to protect people from collapsing floors and a crushing death.

Emergency response measures put in place plans for providing basic necessities to victims of a disaster. These plans can include evacuation, if given sufficient warning and time.

Versions of the above plans can be used for most natural hazards, a big factor being the time period over which the event un-folds. However, some natural disasters have indicators that something big is about to happen— precursor events. For us here in the Midwest, a tornado is one of the most feared events. I haven’t yet lived through one—knock on wood—but others have told me that tornadoes are preceded by a strange darkening of the sky, a sort of green color. If we understand better how the disaster develops, we can better respond to the disaster. Let’s think about a volcanic eruption. What are precursor events?

Tremors and small earthquakes: As magma moves up to the surface, it sets off small earthquakes, rearranging the overly-ing rock.

Gas releases: The decreasing pressure allows trapped gases to escape. Some of these enter the groundwater, altering its chemistry in ways that can be monitored in wells.

Heat flow: The magma is hot, and with sensitive equipment it can be detected. See [here.]

Changes in land surface: bulging and other surface changes may reflect the movement of magma below.  Once the eruption takes place, the hazards take multiple forms:

lahars: Many volcanoes are snow-capped, and the lava rapidly melts it. The water mixes with ash and moves rapidly downhill as mudflows, often tens of feet thick, burying villages and roads below.

pyroclastic flows: Fiery rocks or clouds of glowing ash are blasted out from the volcano, incinerating everything in their path as they rush downhill at hundreds of miles per hour.

debris avalanches: New volcanic material steepens slopes and adds weight, often causing landslides.

bombs: Depending on the type of lava and the presence of water, explosions may toss large rocks high in the air.

So why would anyone choose to live next to a volcano? They are pretty, and the volcanic ash weathers to good soil. Also, eruptions may not occur often enough that people remember or take seriously the danger. Turning a volcano into a national park may be the best use for it, saving lives. And it may be up to geologists and geology students to make the case for doing so.