The landslide occurred on June 23, The landslide occurred where steeply-dipping rocks of late Paleozoic age were undercut by the Gros Ventre River.
Heavy rains and spring snow melt may have been contributing factors as well. The volume that slid was nearly a mile long, 2, feet wide, and several hundred feet thick-estimated at about 50 million cubic yards. In a matter of minutes the landslide moved into the valley and dammed the Gros Ventre River.
A large lake formed behind upstream of the landslide. On May 18,, the natural dam partially failed, and a great flood of water, rock, and debris washed down the valley causing catastrophic damage to the town of Kelly, Wyoming and several ranches in the valley below. At least six people were killed in the flood.
This view is looking down onto the toe area of the Gros Ventre Landslide. Boulders, mostly Tensleep Sandstone, litter the surface of the landslide. They also cover much the stream valley below the slide area-carried downstream in the flood when the natural dam formed by the landslide failed. The forest has grown back since the landslide occurred in Barren areas are locations where there is little or no soil, or where smaller, more recent landslides have occurred.
Left - Glacially polished bedrock in Alaska Basin with glacial erratics resting on the surface. Lehle Glaciers. Pleistocene Ice Age glaciers sculpted the Teton landscape over multiple glacial advances widening V-shaped river canyons into U-shaped glacial canyons, gouging out depressions filled by lakes today, sharpening high peaks, and filling the valley floor with outwash debris.
The most recent advance, known as the Pinedale, lasted from roughly 50, to 12, years ago. Many hikers access the park's high country by traveling up glacial canyons such as Cascade, Paintbrush, Death Canyon and Granite.
Look for features like glacially polished bedrock as you hike through these areas. In an earlier glacial advance, about , years ago, large ice sheets flowed off the Yellowstone Plateau through the Jackson Hole valley, almost reaching Hoback Junction and burying the valley with more than 2, feet of ice.
These glaciers left behind outwash plains of gravel and cobbles that are now covered in sagebrush. Glacial meltwater carried away the fine sands and silts that would have retained moisture and allowed topsoil to form; sagebrush is well adapted to dry soils, so it now covers these outwash plains.
Conversely, conifers cover moraines, which mark the borders of former glaciers. Glaciers carry boulders, cobbles and gravel as they flow and grind up rocky material to the consistency of flour. As glaciers melt constantly at their terminus, they deposit this rocky debris as ridges called moraines. The fine-grained material help soils form and retains moisture, allowing trees to grow. Look for moraines ringing glacial lakes such as Jenny, Taggart and Jackson, as well as some isolated moraines such as Timbered Island.
Glacial features include knife edged ridges on high peaks, U-shaped canyons, sagebrush-covered outwash plains, conifer covered glacial moraines, and a glacially gouged lake. NPS Other Park Resources To learn more, visit Grand Teton's websites on glacial features and current glacier research , as well as the park's geology brochure.
Outside Resources Discover Grand Teton allows viewers to explore the geology of the region through a timeline, earthquakes, rocks and forces. There is a multitude of hiking trails ranging from. Overview The peaks of the Teton Mountain Range are regal and imposing as they make one of the boldest geologic statements in the Rockies. With no foothills to suggest their presence, they rise through steep conifer forests into alpine meadows strewn with wildflowers, past blue and white glaciers to naked granite pinnacles.
The Grand, Middle, and South Tetons form the heart of the range. By traveling a mere four miles north of the town of Jackson, Wyoming, you will be awe struck by the immense size and height of this natural wonder.
These are problems to challenge the minds of generations of earth scientists yet to come. Among the greatest of the park's many attractions is the solitude one can savor in the midst of magnificent scenery. Only a short walk separates us from the highway, torrents of cars, noise, and tension. Away from these, everything seems restful.
Quiescent it may seem, yet the landscape is not static but dynamic. This is one of the many exciting ideas that geology has contributed to society. The concept of the "everlasting hills" is a myth. All the features around us are actually rather short-lived in terms of geologic time. The discerning eye detects again and again the restlessness of the land. We have discussed many bits of evidence that show how the landscape and the earth's crust beneath it are constantly being carved, pushed up, dropped down, folded, tilted, and faulted.
The Teton landscape is a battleground, the scene of a continuing unresolved struggle between the forces that deform the earth's crust and raise the mountains and the slow processes of erosion that strive to level the uplands, fill the hollows, and reduce the landscape to an ultimate featureless plain.
The remainder of this booklet is devoted to tracing the seesaw conflict between these inexorable antagonists through more than 2. Evidence of the struggle is all around us. Even though to some observers it may detract from the restfulness of the scene, perhaps it conveys to all of us a new appreciation of the tremendous dynamic forces responsible for the magnificence of the Teton Range.
The battle is indicated by the small faults that displace both the land surface and young deposits at the east base of Mount Teewinot, Rockchuck Peak fig. Jackson Hole continues to drop and tilt. The gravel-covered surfaces that originally sloped southward are now tilted westward toward the mountains.
The Snake River, although the major stream, is not in the lowest part of Jackson Hole; Fish Creek, a lesser tributary near the town of Wilson, is 15 feet lower. For 10 miles this creek flows southward parallel to the Snake River but with a gentler gradient, thus permitting the two streams to join near the south end of Jackson Hole.
As tilting continues, the Snake River west of Jackson tries to move westward but is prevented from doing so by long flood-control levees built south of the park. Recent faults also break the valley floor between the Gros Ventre River and the town of Jackson.
The ever-changing piles of rock debris that mantle the slopes adjacent to the higher peaks, the creeping advance of rock glaciers, the devastating snow avalanches, and the thundering rockfalls are specific reminders that the land surface is restless. Jackson Hole contains more landslides and rock mudflows than almost any other part of the Rocky Mountain region.
They constantly plague road builders fig. All of these examples of the relentless battle between constructive and destructive processes modifying the Teton landscape are but minor skirmishes. The bending and breaking of rocks at the surface are small reflections of enormous stresses and strains deep within the earth where the major conflict is being waged. It is revealed every now and then by a convulsion such as the earthquake in and west of Yellowstone Park.
0コメント