Denali National Park - Rivers of Ice

The surface of the Muldrow Glacier was for many years the major route into the mountains. A 32-mile-long river of ice, it is fed by three large tributaries, each of which originates in a cirque, or huge, rounded bowl, high in the mountains. Here snow piled up for centuries, every foot of accumulation helping to compact the snow beneath into ice until, under the tremendous pressure, the bottom layer became puttylike and the entire mass began to move downhill.

For millennia the glaciers grew. The leading edges, or snouts, usually moved only as fast as they were forced to by the slow accumulation of snow at the glaciers' heads. But sometimes the action was more violent. The Muldrow, for instance, is a "surging" glacier, one of several in Alaska. Such a glacier creeps imperceptibly for many years, as most glaciers do, until, for reasons not clearly understood, it makes a convulsive forward lunge. During the winter of 1956-57 the Muldrow made a mighty surge, its snout pushing four miles forward. By late 1957, when the energy of the surge was spent, the surface of the lower end had fractured, great chunks and pinnacles of white ice had been exposed from within, and the upper end had sunk 200 feet. The Muldrow was no longer the easy route it had been.

The Awakening Tundra
Although winter is long and cold on the tundra, the land is locked under a cover of snow from October into May, the coming of spring is swift and dramatic. Brown earth appears, moist with melting snow, and is quickly covered by a spreading flush of green: lichens, mosses, fast-growing grasses and sedges, and low matted perennials. Almost immediately, pinpoints and blotches of color, the blossoms of an array of wildflowers, punctuate the landscape.

In May, before the tundra grows soggy, bands of caribou set out through the valley toward their summer feeding grounds beyond the lower passes of the Alaska Range. The year's calves are born along the way and are almost immediately able to keep up with their mothers; those who cannot will probably fall victim to wolves.

Dall sheep, the only pure white wild sheep in North America, also make the hazardous trek across the lowlands. They move with urgency through this domain of wolves and grizzly bears to the rocky, windswept mountain heights, where they reign, sure-footed and surpreme.

Grizzly bears roam the tundra unmolested and ravenous after their long winter sleep. They are for the most part vegetarians, digging the roots of pea vines and other plants in spring, and feeding on greens and flowers throughout the summer and on the plentiful fruits of autumn. But they do not scorn meat. Anything that a grizzly comes across in its travels it may eat, ground squirrels, caribou calves, even moose, are potential food. A grizzly that happens upon a wolf, or even a group of wolves, enjoying the outcome of a hunt will probably move in and take over. The wolves may object, but not for long. A grizzly bear does what it wants to do.