What especially distinguishes the Puyallup Glacier from its neighbors to the north is the great elevation of its cirque; The Carbon, North Mowich, and South Mowich Glaciers all head at levels of about 10,000 feet, but the Puyallup Glacier has its source in the Sunset Amphitheater a full 2,000 feet higher. Encircled by a great vertical wall (fig; 22) that cuts into the Liberty Cap platform from the south, this amphitheater has developed evidently through glacial sapping from a hollow of volcanic origin. From it the Puyallup Glacier descends by a rather narrow chute. Then it expands again to a width of three-fourths of a mile and sends a portion of its volume to the South Mowich Glacier. In spite of this loss it continues to expand, reaching a maximum width of a mile and a total length of 4 miles. No doubt this is accounted for by the heavy snowfalls that replenish it throughout its course.
Its lower end consists of a tortuous ice lobe that describes a beautiful curve, flanked on the north by a vertical lava cliff. A lesser lobe splits off to the south on a wedge of rock.
Immediately south of the Sunset Amphitheater the crater rim of the volcano is breached for a distance of half a mile. (Fig. 22.) Through this gap tumbles a voluminous cascade from the névé fields about the summit, and this cascade, reenforced by a flow from the Sunset Amphitheater, forms the great Tahoma Glacier, the most impressive ice stream on the southwest side. Separated from its northern neighbor by a rock cleaver of remarkable length and straightness, it flows in a direct course for a distance of 5 miles. Its surface, more than a mile broad in places, is diversified by countless ice falls and cataracts.
A mere row of isolated pinnacles indicates its eastern border, and across the gaps in this row its névés coalesce with those of the South Tahoma Glacier. Farther down the two ice streams abruptly part company and flow in wide detours around a cliff-girt, castellated rock massGlacier Island it has been named. (Fig. 22.) The Tahoma Glacier, about a mile above its terminus, splits upon a low, verdant wedge and sends a lobe southward which skirts the walls of this island rock, and at its base meets again the South Tahoma Glacier. Here the two ice streams merge and form a single densely débris-laden mass, so chaotic in appearance that one would scarcely take it for a glacier. Numerous rivulets course over its dark surface only to disappear in mysterious holes and clefts. Profound, circular kettles filled with muddy water often develop on it during the summer months, and after a brief existence empty themselves again by subglacial passages or by a newly formed crevasse. So abundant is the rock débris released by melting that the wind at times whips it up into veritable dust storms.
Beautifully regular moraines accompany the ice mass on both sides, giving clear evidence of its recent shrinking.
SOUTH TAHOMA GLACIER.
The partner of the Tahoma Glacier, known as the South Tahoma Glacier, heads in a profound cirque (fig. 22) sculptured in the flanks of the great buttress that culminates in Point Success (14,150 feet). It is interesting chiefly as an example of a cirque-born glacier, nourished almost exclusively by direct snowfalls from the clouds and by eddying winds. In spite of its position, exposed to the midday sun, it attains a length of nearly 4 miles, a fact which impressively attests the ampleness of its ice supply.
In glacial times the glacier had a much greater volume and rose high enough to override the south half of Glacier Island, as is clearly shown by the glacial grooves and the scattered ice-worn boulders on that eminence. As the glacier shrank it continued for some time to send a lobe through the gulch in the middle of the island. Even now a portion of this lobe remains, but it no longer connects with the Tahoma Glacier.
An excellent nearby view of the lower cascades of the South Tahoma Glacier may be had from the ice-scarred rock platform west of Pyramid Rock. From that point, as well as from the other heights of Indian Henrys Hunting Ground, one may enjoy a panorama of ice and rock such as is seen in only a few places on this continent. (Fig. 22.)
Last Updated: 07-May-2007