The first major section of the field course will follow the historic route of the Oregon Trail, that great emigrant highway route to the West. The idea of a single trail is probably inaccurate since several trails were interwoven, following roughly the same route west at times, and since these trails diverged significantly beyond South Pass in the Rocky Mountains. The Mormon Trail, for instance, paralleled and often overlapped with the main route of the Oregon Trail before splitting away and running into the Great Basin. Initially, however, the main path of all these trails was the Platte River valley, which today passes through the state of Nebraska. We pick up the Oregon Trail approximately near Kearney, NE, along I-80.
For more information on the Oregon and Mormon Trails, visit the following sites:
As we cross Nebraska, we enter into that portion of North America known as the Great Plains. Stereotypically, the plains are flat, treeless, and semiarid. At various locations, however, we will see evidence that the plains are more complex than that, especially in terms of the terrain. Many landforms at a variety of scales challenge the idea of a uniformly flat Great Plains. Note, too, that there are also trees in the region, usually appearing as galeria forests along river courses.
Some of the main landmarks of the Oregon Trail lie in western Nebraska and eastern Wyoming, in the very heart of the Great Plains. Before considering these sites in turn, examine the following map of the area to get your bearings:
Farther west, we arrive at one of the Oregon Trail's most prominent landmarks, Chimney Rock. A key historical site, Chimney Rock was mentioned in more than 9 out of 10 travel diaries of pioneers on the Oregon Trail, making it perhaps the most famous landmarks on the trail. Chimney Rock is also an important geomorphologic feature, containing clues to the erosional history of the Great Plains.
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A view of Chimney Rock as it might have appeared to pioneers is provided below in the form of a watercolor painted by the famed western landscape photographer William Henry Jackson. Jackson painted a number of watercolors of the Oregon Trail, many of which are held by the National Park Service at Scotts Bluff National Monument.
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Several additional views of Chimney Rock appear at the following sites:
Not far beyond Chimney Rock, lies the next major stop on the field trip, Scotts Bluff National Monument. Besides its importance as an Oregon Trail landmark, Scotts Bluff preserves even better than Chimney Rock the erosional history of the Great Plains. The bluff remains as an isolated relic of the former Great Plains surface, now approximately 800 feet higher than the North Platte bottomlands below. From the summit of the bluff (which we visit), you can see the results of the Platte's slow, but steady erosion of the plains. You can also see Chimney Rock in the distance. For more on Scotts Bluff, visit these sites, especially the National Park Service link which contains information on William Henry Jackson.
Just beyond Ft. Laramie, near the town of Guernsey, Wyoming, we'll see some of the most visible evidence of the Oregon Trail yet. This evidence survives in a sandstone ridge that the trail passed directly over. At one point, a soft cliff face served as a "bulletin board" for emigrants who etched their names in the stone. This is Register Cliff. While erosion has weathered away many of the names, others still survive, dating back to the very days of the Oregon Trail passage.
At a nearby location, the actual route of the wagons is clearly visible on this ridge. These are the Oregon Trail ruts, at one point carved about 5 feet into the sandstone. While there are disputes over the Oregon Trails actual location at various points along its route, there is little controversy here. Follow the link below and see why!
Our last major stop on the Oregon Trail is Independence Rock, a dome shaped granite outcropping along the banks of the Sweetwater River. Formerly an intrusive igneous formation, the rock has been exposed by the steady erosion of the Sweetwater of the softer sedimentary rocks that once covered it.
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Besides being an important landmark on the trail, Independence Rock is noteworthy as the great "Register of the Plains," as thousands of emigrants paused here long enough to inscribe their names into the rock's surface. Over time, many of these inscriptions have weathered away, but as you climb on the rock you can still find examples dating to the 1840s and 50s! From atop Independence Rock, you can also see the next site on the trail to the West--Devil's Gate.
Perhaps the most visually stunning feature on the trip (if a trip like this can have but one!) is the Grand Tetons, a tilted, fault-block mountain range that rises up dramatically from the Snake River Valley below. For lifelong-easterners who have never seen real mountains, these are mountains!
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Upper Left: Mount Moran (Source: Wyoming Images).
Upper Right: Grand Tetons and Snake River Valley (Source: Wyoming Images).
Lower Left: The Grand Teton, 13,766 feet (Source: Wyoming Images).
Lower Right: Grand Teton Range—aerial view from the north (Source: Geology Gems).
The real jewel of the field course is our next destination, Yellowstone National Park. Preserved since 1872 as a national park (the first in the U.S. and the world!), Yellowstone is dominated by volcanic activity. Noteworthy are the park's many geysers, hot springs, fumaroles, and mud pots, but evidence of past lava flows and other volcanic features is also visible.
Perhaps the most stunning of the volcanic features are Mammoth Hot Springs, here shown as photographed in 1871 by William H. Jackson while a member of the Hayden survey expedition. Images like this one, as well as the famous paintins by Thomas Moran, helped persuade Congress to create Yellowstone National Park.
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(Courtesy Colorado State Historical Society, #WHJ 1190 F24157, Jackson.)
Another prominent site in Yellowstone is that of the Grand Canyon, an erosional landform scoured from the altered rhyolite of a lava flow. At the head of the stunning canyon is the breathtaking Lower Falls of the Yellowstone, shown here.
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Thoughout the park, evidence abounds of the fires that swept through the region in 1988. The burned areas appear in the map below.
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For much more information on Yellowstone, including images and analysis of the park's volcanic landforms and geology, appear at some of the web sites below:
Before leaving Wyoming as we return east, we visit yet another volcanic feature, Devils Tower. Once the core of a volcano, the stump-like landform has been exposed by the steady erosion of overlying rock. Today, only the more resistant volcanic neck remains, rising sharply from the surrounding plain.
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Devils Tower (Source: Wyoming Images).
Just south-southeast of Devils Tower lies a major outlier of the Rockies, the Black Hills. This massive granite formation—a laccolith—was once covered by layers of sedimentary rock (like many other features we've observed). Erosion of this overlying strata, however, has exposed these igneous rocks. Eroding much more slowly than the surrounding rock, the Black Hills now rise dramatically above the surrounding plains.
Our last major stop on the Great Plains—Badlands National Park—is no less stunning that those visited earlier. Like so many of the previous location, Badlands provides vivid evidence of the geomorphologic history of the Great Plains. This evidence is visible thanks to erosion of the sedimentary deposits of the area, which results in a rugged region of dramatic relief:
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For further information on Badlands and more scenic views, visit these sites: