[Illustration: A. _View west across Jackson Lake. Major peaks,
canyons, and outcrops of sedimentary rocks are indicated by “s.”_]
[Illustration: B. _View northeast; a study in contrast with the
panorama above._]
Three steepsided hills called _buttes_ rise out of the flat floor of
Jackson Hole. They are tilted and faulted masses of hard, layered rock
that have been shaped by southward-moving glaciers. Six miles north of
the boundary turnout is Blacktail Butte, on the flanks of which are
west-dipping white beds. Southwest of the turnout is East Gros Ventre
Butte, composed largely of layered rocks that are exposed along the road
from Jackson almost to the turnout. These are capped by very young lava
that forms the brown cliff overlooking the highway at the north end of
the butte. To the southwest is West Gros Ventre Butte, composed of
similar rocks.
_View west._—
The motorist traveling west along U. S. 26-287 is treated to two
magnificent views of the Teton Range. The first is 8 miles and the
second 13 miles west of Togwotee Pass. At these vantage points, between
20 and 30 miles from the mountains, the great peaks seem half suspended
between earth and sky—too close, almost, to believe, but too distant to
comprehend.
Only from closer range can the motorist begin to appreciate the size and
steepness of the mountains and to discern the details of their
architecture. The many roads on the floor of Jackson Hole furnish
ever-changing vistas, and signs provided by the National Park Service at
numerous turnouts and scenic overlooks help the visitor to identify
quickly the major peaks and canyons and the principal features of the
valley floor. Of all these roadside vantage points, the top of Signal
Mountain, an isolated hill rising nearly 1,000 feet out of the east
margin of Jackson Lake, probably offers the best overall perspective
(fig. 3). To the west, across the shimmering blue waters of Jackson
Lake, the whole long parade of rugged peaks stretches from the north
horizon to the south, many of the higher ones wearing the tattered
remnants of winter snow. From here, only 8 miles away, the towering
pinnacles, saw-toothed ridges, and deep U-shaped canyons are clearly
visible.
Unlike most other great mountain ranges, the Tetons rise steeply from
the flat valley floor in a straight unbroken line. The high central
peaks tower more than a mile above the valley, but northward and
southward the peaks diminish in height and lose their jagged character,
gradually giving way to lower ridges and rounded hills. Some of the
details of the mountain rock can be seen—gnarled gray rocks of the high
peaks threaded by a fine white lacework of dikes, the dark band that
cleaves through Mount Moran from base to summit, and the light brown and
gray layers on the northern and southern parts of the range.
At first glance the floor of Jackson Hole south of Signal Mountain seems
flat, smooth, and featureless, except for the Snake River that cuts
diagonally across it. Nevertheless, even the flats show a variety of
land forms. The broad sage-covered areas, low isolated hills, and
hummocky tree-studded ridges that form the foreground are all parts of
the Teton landscape, and give us clues to the natural processes that
shaped it. A critical look to the south discloses more strange things.
We take for granted the fact that the sides of normal valleys slope
inward toward a central major stream. South of Signal Mountain, however,
the visitor can see that the Snake River Valley does not fit this
description. The broad flat west of the river should slope east but it
does not. Instead, it has been tilted westward by downward movement
along the Teton fault at the base of the mountains.
_View south._—
About a million motorists drive south from Yellowstone to Grand Teton
National Park each year. As they wind along the crooked highway on the
west brink of Lewis River Canyon (fig. 1), the view south is everywhere
blocked by dense forest. Then, abruptly the road leaves the canyon,
straightens out, and one can look south down a 3-mile sloping avenue cut
through the trees. There, 20 to 30 miles away, framed by the roadway,
are the snow-capped Tetons, with Jackson Lake, luminous in reflected
light, nestled against the east face. This is one of the loveliest and
most unusual views of the mountains that is available to the motorist,
partly because he is 800 feet above the level of Jackson Lake and partly
because this is the only place on a main highway where he can see
clearly the third dimension (width) of the Tetons. The high peaks are on
the east edge; they rise 7,000 feet above the lake but other peaks and
precipitous ridges, progressively diminishing in height, extend on to
the west for a dozen miles (fig. 14). Giant, relatively young lava
flows, into which the Lewis River Canyon was cut, poured southward all
the way to the shore of Jackson Lake and buried the north end of the
Teton Range (figs. 13 and 53). South of Yellowstone Park these flows
were later tilted and broken by the dropping of Jackson Hole and the
rise of the mountains.