Yellowstone National Park - The Mountaintop World

On the flanks of nearby mountains, the tapestry diminishes, grows ragged, and finally disappears. The peaks look bald and dead. But here on Mount Washburn grow the gnarled whitebark pines that survive on all but a few of the highest peaks. Built to withstand wind, dryness, and heavy snows, they shelter one another from wintry blasts. Between and above them is the alpine tundra, where pikas scurry among rocks, gathering greenery to live on in winter, and where regal bighorn sheep move confidently on windswept ridges; every summer, a herd makes its home on Mount Washburn's slopes, the males holding their heads high to bear up the weight of their massive crowns of horns. Here, too, tenacious, but fragile enough to be erased by footsteps, are the lichens, grasses, and miniature flowering plants of the alpine tundra. For a few weeks in July, the tundra blooms with alpine buttercups, clover, forget-me-nots, phlox, and other tiny blossoms.

Distant mountain ranges meet the horizon in all directions. Northward are the snaggled, snowy Beartooths; to the west, the Gallatins; far to the south are the white-capped Tetons; and stretching along the park's eastern boundary is a range of barren peaks called the Absarokas. They, like the Mount Washburn, are remnants of ancient volcanoes that now mark a rim of the Yellowstone Caldera; they form a wall between the pocket in which Yellowstone lies and the Great Plains that stretch eastward to the Mississippi.

At the foot of the Absarokas in the shining expanse of Yellowstone Lake. Measuring 20 miles long, with a surface area of 136 square miles, it is almost an inland sea. It is a cold lake, its depths never warming to 40º F. Cutthroat trout thrive in its clear waters. Water birds ride the winds above, including many kinds that one associates with the ocean. Cormorants range the waves, terns wheel and soar, and gulls hang motionless on the wind. White pelicans fly low over the water, their long wings sweeping rhythmically in slow, powerful strokes. Ducks bob in large flotillas, and flocks of geese fly purposefully along the shore, honking as they go.

Like any large body of water, Yellowstone Lake has many moods. On calm summer nights it can reflect the moon and stars flawlessly. But when gales churn its surface, whitecaps 10 feet high can smash against the gravelly shorelines or eat away at bluffs until trees lose their footing and fall into the churning waters. In winter, it is a vast Arctic tableland, and sweeping winds pile 20-foot snowdrifts over islands and along the shoreline.

Lanscape of the Sky
Because of Yellowstone's elevation, generally between 7,000 and 8,500 feet, the air tends to be clear and dry during the summer: pleasantly warm in the sun, sharply cool in the shadows, often chilly at night. Puffy white cumulus clouds, beautiful against the deep blue sky, drift eastward overhead. But because Yellowstone is in a pocket surrounded by high peaks, its weather can change in odd ways.

Sometimes, in the middle levels of the atmosphere above the gentle cumulus, strange, lens-shaped white clouds ride invisible winds. These are mountain wave clouds, formed as air flows up over westward peaks, cools, and condenses into saucer shapes. Often they presage nothing, simply forming and dissipating for hours in the undulating atmosphere. But on other days they are the forerunners of thunderclouds that boil quickly upward into the clear western sky.

In the evening is warm, a luminous wall of thunderheads may even form over the eastern edge of the park, fed by hot air that rises along the front range of the Rockies. Then Yellowstone Lake is bathed in shadowless white light reflected from the billowing clouds, and everything becomes perfectly still. For long, hushed, breathless moments the park waits while thunder rolls and lightning flickers through the towers and battlements that seethe in the east. Often the storm remains only a distant and dramatic presence; but often, too, in apparent contradiction to the normal scheme of things, the thunderhead spreads backward, westward, over the park, and the air turns violent.

From whatever direction they come, Yellowstone's thunderstorms possess a stunning power to mix the summer air, lifting it and then pushing it earthward again. Rain is sucked high into the atmosphere, where the air is below freezing, and then flung down in the form of sleet, or hail, or even snow. Temperatures can drop from 75º F to the low 30's in less than an hour, transforming a warm, dry afternoon into a cold, wet evening. By morning the temperature, even in July or August, is likely to be below freezing, and snow may cover the ground. In early June or late August, such storms sometimes dump several inches of it.