#snowslide

book cover - Snowslide - 1950

Avalanche, Silver Plume, Colo.

By Norman Clyde

Norman Clyde was a young high school principal in Independence, California in the 1920s. Clyde had been inspired by the writings of John Muir and became well known for his high country exploits. By the age of fifty in 1935, Clyde was the veteran of more than six hundred mountain ascents. During a "vacation" in Glacier National Park, Clyde scaled thirty-six peaks in an many consecutive days. We included a wonderful story he wrote, "The Search for Walter Starr", in The Pacific Crest Trailside Reader: California.

The short piece below is from a short tome that Clyde authored in 1962, "Close Ups of the High Sierra", focused on avalanches in the Sierra. It touches on a subject that is especially relevant to PCT hikers who enter the Sierra earlier and earlier in the year.

(Walking through an avalanche field in the Sierra where the trees have been snapped off by an avalanche. Photo credit: Rees Hughes)

Avalanches are much more numerous in the High Sierra during the winter and spring than those who have not spent considerable time there are aware. Their number varies greatly being much ore frequent and of greater volume during seasons of high precipitation. That comparatively slight damage has been done to property and few lives lost is due, in large measure, to the fact that most occur when there is little property to destroy and no person in the pathway.

Snowslides in the higher portions of the mountains take place most frequently in couloirs or chutes. After heavy snowfalls, numerous slides course down. . . . In spring, after a storm, almost as soon as the sunshine strikes new snow, it may let go and come rushing down the couloir. After a storm in May, I have seen as many as a dozen slides coursing down as many couloirs in beautiful snowfalls.

Avalanches take place on smooth slopes on steep mountain faces. Powder snow does not cling to these faces. If it happens to be wet, as sometimes happens, even in the High Sierra, a considerable amount may adhere to the rocks. As the temperature warms this usually sloughs off in avalanches.

Many slides to not reach the underlying terrain. Except on protected slopes or basins, snow that falls in the Sierra may be packed by the wind or thaw on the surface. As the temperature drops, a crust is formed. If alternate thawing and freezing continues, neve, or granular snow is formed. By spring, much of the snow, particularly on exposed slopes is of this form.

Rough slopes which would prevent snow from sliding are sometimes smoothed over. Should a heavy snow fall of such a surface, particularly if the slopes is above 45 degrees, the danger of a slide is great. Many of the spring slides are of this type.

Avalanches usually start slowly. A crack runs along, then slowly widens and a sheet of snow begins to move. Once started, the acceleration may be great. If it travels three thousand feet down a steep slope, it may reach express train speed. Its momentum being sufficient, it may run across several hundred yards of terrain at the foot.

On one occasion, weary of slogging through wet snow well up to my knees, I hit upon the idea of starting miniature snowslides and riding them. This I did by sitting down heavily, causing the layer of new snow to begin to slide. The acceleration was rapid. Eventually I struck a shadowed area, where an icy crust had formed.