High in the south wall of American Fork Canyon, in Utah's Wasatch Range, three caves joined by tunnels hold some of the finest limestone formations in the West. Timpanogos Cave National Monument, set aside in 1922, protects them — and the canyon wall they sit in, a stack of rock running from the Precambrian to the Cenozoic.
The monument in brief
| Established | October 14, 1922 |
| Size | 250 acres |
| The caves | Hansen, Middle and Timpanogos, connected by tunnels; 5,600 feet in all |
| The canyon | a steep, narrow limestone gorge with cliffs, avalanche chutes and pinnacles |
How the caves formed
The caves are in the Deseret Limestone, of Mississippian age. Slightly acidic groundwater, moving along its paths through the rock, slowly dissolved the limestone and opened voids that became the caves. The same chemistry runs in reverse elsewhere: limestone dissolved in one place comes out of solution in another and builds speleothems — stalactites, stalagmites and the other cave formations.
The canyon walls
| Wall | Rocks |
|---|---|
| North side | the Precambrian Mutual Formation — up to 10,000 feet of quartzite and coarse conglomerate with some limy shale and slate |
| South side, where the caves are | Paleozoic layers: the Cambrian Tintic Quartzite, Ophir Limestone and Maxfield Limestone, and the Mississippian Fitchville Formation, Gardison, Deseret, Humbug and Great Blue limestones |
| Younger | Mesozoic and Cenozoic sediments such as the Tibble Formation, and the granite of the Little Cottonwood stock |
All of it is broken by faults of both kinds — normal and reverse — at every scale. The monument belongs to the Basin and Range physiographic province.
The Park Service's Geologic Resources Inventory has published a geologic map and report for the monument, free on the NPS DataStore. Fossils are protected by the Paleontological Resources Preservation Act of 2009.
Sources
Written from "NPS Geodiversity Atlas—Timpanogos Cave National Monument, Utah", National Park Service Geologic Resources Division, a work of the United States government in the public domain, which cites Thornberry-Ehrlich (2006).
Licence: CC0 1.0 (public domain) · Adapted from www.nps.gov
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