Hi, I’m Holly Strand from Stokes Nature Center in beautiful Logan Canyon.
For awhile now, I assumed that living on a bench on the eastern edge of Cache Valley, meant that I was living on the very western edge of the Rocky Mountains. But is the Bear River Range really in the Rockies? Are the Wasatch Mountains in general?
Peakbagger.com, which features a hierarchical system of mountain range classification, says that the Utah Rockies are represented by two main mountain massifs the Uintas and the Wasatch.
But according to Halka Chronic, author of Roadside Geology of Utah, we are definitely out: The Wasatch Range, steeply faulted on its western side, was once considered to be part of the Rocky Mountains, formed in the late Cretaceous to early Tertiary period. The Wasatch is now known to be younger than the Rockies and is considered the easternmost part of the Basin and Range region. Chronic identifies Heber Valley as the easternmost basin of the Basin and Range. The Basin and Range is a huge arid region in Utah, Nevada and adjacent states. Within it, narrow north-south oriented mountain ranges alternate with valleys filled with erosional sediment.
I turned to some Utah State University geologists for help. As usual, the answer to what I think is a simple question turns out to be complicated. Sue Morgan considers the Wasatch to be the easternmost edge of the Basin and Range because the mountains were formed by normal faulting characteristic of the Basin and Range. But, she points out, that the Utah Geological Survey considers the Wasatch to be part of the Middle Rockies.
Dave Liddell says the answer to my question is a matter of scale. If you are looking at North America from space those of us on the Wasatch Front could justifiably consider ourselves located on the edge of the continental–scale Rocky Mountain system. However, the closer look, you have to start taking into consideration lots of fine scale variations and categorizations; this makes drawing a boundary between the Rockies and the Basin and Range province extremely complex. Liddell would put Cache Valley in the Basin and Range because of its formation by pull apart tectonics. The rest of the Wasatch Front is Basin and Range for the same reason. But most geologists put Bear Lake in the Rockies. So perhaps the Wasatch is a large transition zone.
Next time the subject comes up—and there’s no guarantee that it will ever come up—I’m probably going to favor the argument that the Wasatch Mountains are outside the Rockies and that most Utahns live in the Basin and Range region. But if some of you Wasatch Front residents really want to live at the foot of the Rockies, that’s fine too–you can cite the Utah Geological Survey. Now that I decided to go with Basin and Range, I’ll want to find out more about the plants and animals that live here. So you can expect to hear more about them in future programs.
For Wild About Utah and Stokes Nature Center, I’m Holly Strand.
Photo: Courtesy Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC http://visibleearth.nasa.gov/view.php?id=62272
Text: Stokes Nature Center: Holly Strand
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