Grand Teton National Park

Front 1

Name at least two specific kinds of crystalline rock making up the highest parts of the Teton Range. Using a term from the geologic time scale, state how old these rocks are. Why are younger rocks not present at the top of the range?

Back 1

There are layered gneisses, granitic gneisses, and granites and also pegmatites. Rocks are from Precambrian time. The older rocks were accumulated to the top during orogenic activities of the tetons. Also faulting caused displacement of younger rocks.

Front 2

Explain how tectonic compression and tectonic extension have each contributed to the uplift of the Teton Range. Include the kind of faulting. Which type of tectonic activity occurred first? What role did the Laramide orogeny play in the uplift of the range?

Back 2

The Teton fault is a steeply dipping normal fault. Tectonic compression was first. First, tensional forces split apart the two large crustal blocks and tiled them toward the west, with the mountain block hinging up and the eastside block sliding down. The compressive forces of the Laramide orogeny initiated buckling along a northwest-southwest trend and broad uplift throughout the region (late cretaceous). Mountains were raised higher as orogeny intensified with more folding and faulting.

Front 3

Explain the roles of the Teton fault and the Buck Mt. fault in forming the Teton Range and Jackson Hole in Grand Teton National Park.

Back 3

The highest mountains of the region were elevated by Reverse Buck Mt. Fault. Buck Mt. was a result of orogenic activity that preceded the normal Teton fault late of the Tertiary time. The crest area that had been raised by reverse faulting was later elevated by normal faulting to its present height. Additionally, the Teton Fault is a steeply dipping normal fault.

Front 4

Describe four ways that glacial activity has formed lake basins (the low areas occupied by lakes) in Grand Teton National Park.

Back 4

Ice eroded depressions in bedrock, cirques and rock basins, glacial troughs and morraines.

Front 5

Describe four ways that glacial activity has formed lake basins (the low areas occupied by lakes) in Grand Teton National Park.

Back 5

1) Two-Ocean Lake= left by Bull Lake glaciation
2) Emma Matilda Lake= left by Bull Lake glaciation
3) Burned Ridge moraine=glaciation
4) Jackson Lake=largest body of water

Front 6

The Gros Ventre landslide in 1925 near Grand Teton National Park profoundly changed the local stream drainage and ultimately killed six people in the town of Kelly five miles from the landslide. The disaster was in two stages and the fatalities actually came two years after the slide itself. Outline the geologic events that generated this slide and the later fatalities.

Back 6

Saturation of sedimentary rock layers and undercutting of the slope by the Gros Ventre River that left the base of the slope unsupported; rockslide triggered by tremors, moved several cubic miles of rock and debris down Sheep Mountain and across the Gros Ventre River valley; slide dammed the river, eventually giving way two years later, flooding the town of Kelly