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Mount St. Helens
by Leslie Whitaker

On May 18, 1980, the sleeping giant awoke inside Mount St. Helens with devastating force. Since 1857, there had not been an eruption, but during the winter of 1979 and 1980, it became apparent that the long sleep might be coming to an end. The chronological list of events that led up to the eruption is below. For more detailed information about the recovery of Mount St. Helens consult our Mount St. Helens recovery paper, reprinted with permission of Mount St. Helens National Monument.

Mid-March: Progressively stronger earthquakes occurred. Inside the old crater, two explosions open new craters and a high plume of ash and steam escaped.

March 31: A new vibration pattern signaling the movement of fluids and gases inside the mountain began.

Late-April: A bulge began to appear on the north side of the mountain. This resulted from moving magma within.

May 12: The bulge grew to 60 feet high.

May 18: Fishing season began on this Sunday. Volcanologist David Johnston was at an observatory station five miles north of the mountain. At 7:00 am he reported that there was no change in the recent readings.

May 18: At 8:32 am, two things happened in quick secession. First, the bulge collapsed, in a debris avalanche, following a large mile deep earthquake. Then the superheated water (600 degrees Fahrenheit) within that bulge burst into steam as the pressure of the earthen shell was released. Rocks, soil, and ash shot into the air and a dozen miles to the north. The steam mixed with mud and formed a mass moving down the mountain, leveling everything in its path. This muddy mixture is called pyroclastic flow. The force of the blast was augmented by the load of rocks to a murderous strength, shearing off trees level with the ground. Everything in its path was leveled and sand blasted. Spokane is 200 miles east of the volcano and the ash cloud threw the city into total darkness at midday.

David Johnston and fifty-six other people did not survive this eruption.

When the ash cleared and the wind quieted and the mud flow stopped, the beautiful mountain was changed. One thousand two hundred feet of its cone was blown off the mountain, primarily on the north side. Although much of the rock fell back into the crater, 1.7 billion tons of ash were deposited on ten states. This fall out destroyed the fields for that season’s planting, but enriched the soil for future agriculture. The forest in the path of the Wind of Rocks and the mud slide was leveled. Many predicted that it would be a century before life would appear again.

However, others watch hopefully and waited to see what would come next. They did not have long to wait for the first signs of returning life. Even in the direct path of the blast, the roots of plants survived and sprouted. Shoots pushed up through the ash. Firewood, one of the first colonizers after a forest fire, appeared. Large animals were killed, but small animals survived: chipmunks, frogs, ants lived through the eruption in their buried homes below the ground or in rotting logs. The spores of fungi were opened by the heat of the eruption and the fungi grew.

The work of gophers was interesting to watch because it demonstrates how the earth and the animals interacted after the eruption. Gophers usually tunnel searching for food underground. One breed of gopher, the pocket gopher, lives on Mount St. Helens. A few of them survived and their efforts to dig new holes and find new food sources proved vital to the reclamation of the land for life. As they dug through the soil under the smothering ash, they kicked piles of this soil out onto the surface and formed piles of good soil where seeds could find a hospitable environment and let plants grow. One such plant that took root was the fireweed, shown here.

Woodpeckers were delighted with all the dead fall trees. They made holes, ate insects, laid eggs, and then deserted the holes in the trees. The mountain bluebirds need holes in trees to raise their young, but they can’t make their own. Therefore, the deserted woodpecker holes made nesting places for the mountain bluebird.

The healing of the mountain is beginning with the small threads of the web of life. Ecosystems are rebuilding in this land. In a century, there will not only be life on Mount St. Helen, but there will be a whole new forest. Unless there is another eruption.

Pyroclastic Flow

It is a common misconception that lava is the most dangerous thing about a volcanic eruption. The hot mud that is released from many volcanoes prior to the lava is the real killer. This superheated mud, called the pyroclastic flow, is devastating. This superheated flood traveled as fast as 80 miles an hour, destroying everything in it's path.

Debris Avalanche

The large land slide that preceded the release of the lava is the debris avalanche. The debris avalanche at Mt. St. Helens was the largest in recorded history. Even if it had not been mixed with hot water, making it the pyroclastic flow, it would have been devastating.

Introduction - Magma, Lava, and Mountain Formation - Predicting Volcanoes - Tectonic Plates - Mt. St Helens - Mount St. Helens Recovery - Volcanoes: Good, Bad or Both