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New geological research shows that the mountains of Great Basin National Park took millions of years to form. The southern Snake Range, the range at the heart of the park, was built over the past 50 million years by periods of intense extension — the stretching of the Earth's crust.
Stretching the crust created many faults, breaks along which rocks move up and down. The faults brought rocks from below up to the surface, and rain, snow, ice and wind then carved them into the range seen today.
One episode or several?
Geologists had not been sure whether the range formed in a single period of stretching or in several. To find out, Sarah Evans of the University of Nevada, Las Vegas, and her colleagues combined computer modelling with new laboratory analyses of rocks from the park and similar analyses by other researchers, to work out when faulting happened. The answer: several episodes.
| Episode | When | What else happened |
|---|---|---|
| First | from about 50 million years ago, for around 12 million years | |
| Second | about 33 to 23 million years ago | intense, probably explosive volcanic activity in east-central Nevada and west-central Utah; volcanic rocks from this time can be seen just south of the park, in parts of the Highland Ridge Wilderness |
| Third | about 23 to 8 million years ago |
Still stretching
The crust is still stretching along faults in and near the park. The time involved is hard to grasp, but the research has helped geologists understand a little more about how this range came to be.
Words on this page from people and organisations outside the federal government are paraphrased; rewritten in hubnx's own words.
Sources
- Sarah Evans, University of Nevada, Las Vegas, "Figuring out How the Southern Snake Range Formed," The Midden (Great Basin National Park), vol. 15, no. 2, winter 2015, National Park Service. https://www.nps.gov/articles/000/figuring-out-how-the-southern-snake-range-formed.htm
- The article's photograph, supplied by the author, is not reproduced here.
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Licence : CC0 1.0 (domaine public) · Adapté de www.nps.gov
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