Nature Notes

Vol. X November - 1932 No. 11

The Reason Why

About noon on Friday, October 14, a family of park visitors who had motored from Seattle were lunching at the parking area near the Nisqually Glacier Bridge. From the steep walls of that glacial gorge reverberated the dull roar of the river a short distance away. On the wings of a lazy wind thin wisps of fog had gathered overhead to shut out the sky and render spectral-like the outlines of the canyon walls and the trees that clung tenaciously to the crevices in these rocky battlements. At the head of the valley, some half mile away and choking the spectrum between the steep cliffs was the snout of the Nisqually Glacier, black, and ugly with its tons of rock debris that had been brought down by the moving ice in ages past. Its appearance was even more gloomy and forbidding in the half light of the foggy day.

Suddenly our visitors were conscious of a dull roar, a distant rumbling of greater magnitude than it was possible for the waters of the turbulent Nisqually to produce. Curious as to its cause one of the men in the party rose to his feet and turned toward the source of the disturbance. He cried out! The others jumped up and likewise saw - as they described later - a "wall of rock and water one hundred feet high rushing down upon them!" Those of us who viewed the results of this freak of nature later consider it fortunate that our visitors escaped without harm. As it was they were milling about in a foot or so of murky water before their car was started and the scene was left behind. Apparently the phenomenon was as short lived as it was sudden for the force of the rushing water with its tons of rock was soon spent. But it left disaster in its wake and the first to view the scene looked upon a very different sight than had, for many ears, been customary in the region of the Glacier Bridge. The river bed was a shambles, the channel scooped out and great boulders strewn about like so many peas. A large section of the trail, over which thousands of visitors trek annually to a point near the snout of the glacier, was washed out and the center span of the concrete bridge itself, which weighs about forty tons, had been swept nearly a mile down stream. A mass of great boulders was strewn about the parking area, and the snout of the glacier, instead of being dirty with the accumulation of rock debris, was now white - having been scrubbed into respectability by the mass of water that had plunged over its face.

Nisqually Glacier

The question, "How did it happen?", is a natural one. And so the ascertain the reason for the Nisqually's unorthodox behavior Superintendent Tomlinson, accompanied by Park Engineer Waterhouse, Landscape Architect Davidson, and the writer journeyed to the glacier some days later. It was evident that the force of the wash had come from somewhere upon the upper surface of the ice as the rock was very perceptibly washed of glacial till. And so, after scrambling up the steep cliff of loose material near the snout, we found ourselves standing on the ice near the edge of the 200 to 250 foot precipice which was the glacier's snout. Stretching upward along the ice rose a series of small steps or catch basins, all partially surrounded by morainal material. The force of a rushing stream was everywhere apparent but the effect of this force was more evident toward the snout face - for the water, gaining momentum as it swept along had added power to sweep more rock from the ice. We walked along upstream on the ice and along the crests of undisturbed moraines and the series of catch basins persisted. Finally, some quarter to one-half mile from the snout and along the west side of the glacier with the canyon wall to one side and a high moraine to the other we saw a large depression - the uppermost of the catch basins. A great scar of freshly exposed earth on the canyon wall near the head of this large basin was seen and it was evident that the catastrophe had its origin at that point.

For some days previous to this time this region had been subjected to an exceedingly heavy rainfall and, as we observed the result, we attempted to piece together the fragments of the story from the facts that were exposed to view. It was finally concluded that the movement, settling and melting of the ice in years past had formed the catch basins which were in turn modified or enlarged by running water from melting ice. Secondly, water gathered in the series of small dams both from melting ice and the current of heavy rainfall. The result was due to the slide on the canyon wall that acted as a detonator to set the whole mass of heretofore stagnant water in motion. The disturbance in the large pool, caused by the slide, broke over the moraine that served as a dam. The rushing water took it completely out and as it plunged into the lower basin its lower dam in turn gave way. And so each catch basin in turn was flooded and washed out. But the greatest momentum did not result until the huge mass of water plunged over the ice cliff at the snout. Then, no doubt, with a Niagara-like roar it swept all before it, gathering up great rocks and carrying tons upon tons of boulders smashed into the bridge a half mile below to add it to its accumulated debris. Once the peak of the flood had passed, once the crest of that great wave of rock and water had swept by, the Nisqually again pursued a more normal course.

And thus did Mother Nature, with one sweep of her paw demonstrate quite forcibly the power that was here. And once again man's pigmy might was put to shame. But, like a spider weaving new strands into a web that had been torn and broken, a force of men was soon at work clearing away the debris, hauling in great logs on trucks and assembling equipment to again bridge the stream. Within a week after the Nisqually struck its turbulent waters were again spanned by a sturdy log bridge.

Lodgepole pine cones

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