Grand Teton National Park

To anyone who loves mountains, one name keeps coming to mind: the Tetons. The grand Tetons. For grand they are. While they are higher peaks elsewhere in the Rockies, none quite match the rugged majesty, the raw, wild beauty of this range. Bold, jagged spires of rock, the Tetons reach high into the Wyoming sky as if to snag the passing clouds.

The peaks are all the grander for their setting. To the east of the mountains lies Jackson Hole (fur trappers of the last century referred to mountain-rimmed valleys as "holes"). From this basin the Tetons rise abruptly, with no intervening foothills, to neck-craning heights, a solid mountain rampart towering some 7,000 feet above the valley floor. And then there are the lakes, Jackson Lake, Jenny Lake, and more. The mirrored images of the peaks in their waters seem to double the height of the mountain wall.

Winding through this lovely valley, like a silver thread of continuity, is the Snake River. A profusion of wildlife flourishes all along its course and throughout the park. Ospreys nest in the weathered skeletons of dead trees by the riverside, as do bald eagles. Otters play on the riverbanks or glide gracefully through the water. Along tributary streams, the small ponds created by beavers are favored feeding spots for moose. The great beasts are often seen standing flank-deep, sometimes even neckdeep, in the ponds, munching on aquatic plants. The park's lodgepole pine forests are home to elk and mule deer, while the sagebrush flats of Jackson Hole are preferred by pronghorns. Black bears wander through the valley forests and on the lower mountain flanks, and grizzly bears are sometimes sighted in the northern reaches of the park. Coyotes, mountain lions, lynx, martens, bobcats, badgers, and a host of smaller animals also find refuge in this rugged wilderness. And above it all, always there, looming over the scene, sensed even when hidden within a shroud of clouds, are the Tetons, the newest of the many ranges that make up the Rocky Mountains. Less than 10 million years old, geologically the Tetons are mere babes; the rest of the Rockies average 60 million years in age.

Youthful mountains, ancient rocks
Five to nine million years ago there were no mountains on this spot. The landscape of what is now western Wyoming was a gently undulating plain, partly forested, partly covered with lush grasslands.

Though it must have seemed a peaceful scene, there was an ominous flaw: trending north-south across the countryside was a zone of weakness in the earth's crust, an area some 40 miles long. The birth of the mountains probably began with modest tremors that culminated in a violent earthquake, the result of a slippage of the rocks on either side of the fault. As the land shuddered in the quake, a great block of the earth's crust to the west of the fault tilted slightly upward. The land to the east simultaneously slipped down.

Birds and beasts no doubt fled in terror as the earth trembled and a great growling roar filled the air. Then when the quake ended and all was still again, a new feature marked the face of this land, a ridge. Even if a comprehending mind had been present to witness these events, however, it is doubtful that this relatively small disturbance of the earth's crust would have been recognized as the first stage in the creation of a massive mountain range.

Centuries may have passed before the earth quaked once again. There may have been days and weeks of nearly constant tremors, followed by decades or even centuries of quiescence. But with each new upheaval, the steep escarpment that was to become the eastern face of the Tetons rose higher into the sky, and the floor of the future Jackson Hole slipped slightly downward.

Neither the number nor the magnitude of each one of these mountain-building crustal movements is known, but the accumulated results over millions of years were truly staggering: scientists estimate that total vertical displacement along the fault has been about 30,000 feet. Why, then, do the peaks rise only 7,000 feet above the valley floor today? This has happened because, though the upheavals were intermittent, erosion has been constant. Ever since that first little ridge appeared across the landscape, running water, seasonal freezing and thawing, and other forces of erosion have been grinding away the newly exposed rocks and depositing much of the debris on the subsiding valley floor. Over the eons, thousands of feet of sandstones, limestones, and volcanic rock layers have been stripped away. What remains today is primarily massive formations of granite, gneiss, and schist that once lay hidden deep beneath the surface of the earth. Born of intense heat and pressure in the earth's interior, these ancient basement rocks are about 2½ billion years old.

Tough and resistant as this steel-hard bedrock may be, it too has succumbed to the forces of erosion, especially moving ice. Two times in the last quarter-million years, worldwide climatic changes have resulted in extensive glaciation over much of North America. During these glacial periods the summer sun no longer melted all of the winter's snow and gradually, over the centuries, large ice fields accumulated among the peaks and sent glaciers spilling down the slopes. Moving slowly but steadily under their own ponderous weight, the glaciers chipped and scoured and scraped away at the hard granitic rocks, sharpening and faceting the peaks into those jagged forms that are so familiar today: Mount Owen, Teewinot Mountain, Middle Teton, South Teton, and towering above all the rest, the majestic spire of Grand Teton.