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Theodore Roosevelt National Park

Geologic Setting

Location Map of Theodore Roosevelt National Park.
Figure 1. Location Map of Theodore Roosevelt National Park.

Theodore Roosevelt National Park is situated mostly within the confines of the Little Missouri River valley in the remote southwestern corner of North Dakota (figure 1). This part of the Great Plains hosts a landscape that has changed little since 1883 when 24- year- old Theodore Roosevelt came west to hunt buffalo (figure 2). The park commemorates Theodore Roosevelt, the 26th U.S. president, who began to develop his conservation ethic in this place. The setting made a deep impression on the young man and influenced his presidential administrative policy, which promoted access to and sustainable use of public lands.

Photo of Bison in the South Unit Crossing the Little Missouri River.
Figure 2. Bison in the South Unit Crossing the Little Missouri River. When Theodore Roosevelt was 24 years old, he came to the region to hunt buffalo. The rugged landscape matched Roosevelt's individualism and influenced his thinking. NPS photo by Dave Krueger.

The Little Missouri River flows northward from Devils Tower and the Black Hills past Theodore Roosevelt National Park and on to the confluence of the Missouri River. The Missouri Plateau section of the Great Plains (figure 3) reflects the thorough dissection of the landscape by the Missouri River and its tributaries. The Little Missouri River flows through the South Unit of the park, past Roosevelt's ranch site, and into the North Unit where it turns abruptly eastward and joins the Missouri River about 80 km (50 miles) away (figure 4).

Map of Physiographic Areas of the Great Plains.
Figure 3. Physiographic Areas of the Great Plains.

The Missouri River and its tributaries (e.g., the Little Missouri River in North Dakota and the Yellowstone River in Montana) carved the Missouri Plateau into confined valleys, broad upland surfaces at many levels, and terraces along the rivers. Locally, high buttes rise above the uplands; these are remnants of former interstream divides. Continental ice sheets also dammed many tributary valleys, forming large lakes (Trimble 1993). Recession as a result of badlands development has widened some of the area's larger valleys.

The Little Missouri River valley is part of the Missouri Plateau of the Great Plains, which consists of two distinct sections: glaciated and unglaciated (figure 4). The boundary between the sections occurs in the park and is marked by glacial erratics (boulders) and cobbles. To the north of this glacial limit, much of the Missouri Plateau is a plain of little relief with muted landforms covered by a thick blanket of glacial debris. To the south the unglaciated Missouri Plateau displays the greatest variety of landforms of any section of the Great Plains (e.g., small mountains, plateaus, river valleys, and badlands) (Trimble 1993). Most of Theodore Roosevelt National Park is situated on the unglaciated Missouri Plateau.

Detailed maps of the North and South Units in Theodore Roosevelt National Park.
Figure 4. Detailed maps of the North and South Units in Theodore Roosevelt National Park.

Precipitation in the region comes as sudden showers, and storms commonly drop several inches of rain per hour (Opdahl et al. 1975). This sudden influx of precipitation causes runoff and rapid erosion of the poorly consolidated sediments, forming highly dissected badlands topography. In addition, fused then broken beds of burnt coal facilitate erosion during runoff events. Seasonally, small tributaries flow down the steep valley sides along the Little Missouri River, cutting into the strata of the Fort Union Group: shales, clays, sandstones, silts, and lignite of the Bullion Creek and Sentinel Butte formations.

In general, the shales and clays are gray to brown, and the sandstones tend to appear yellowish orange to buff and tan. Blue bentonite in the Sentinel Butte Formation adds another colorful layer to the landscape. Lignite is dark brown to black. Possibly the most noticeable strata in the park are the red beds, locally called "scoria," but more correctly called "clinker." The colorful, interbedded strata on the hillsides of the park add much to the scenic beauty of the badlands.



References:

Opdahl, D. D., W. F. Freymiler, L. P. Haugan, R. J. Kukowski, B. C. Baker, and J. G. Stevens. 1975. Soil survey of Bowman County, North Dakota. Bismarck, ND: U.S. Department of Agriculture Soil Conservation Service, North Dakota State Office.

Trimble, D. E. 1993. The geologic story of the Great Plains. Medora, ND: Theodore Roosevelt Nature and History Association.

updated on 08/06/2007  I   http://www.nature.nps.gov/geology/parks/thro/geol_setting.cfm   I  Email: Webmaster
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