Interesting Features
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Features
The hydrocarbon content of some of the Pierre shale is high and has ignited occasionally in the Spring due to friction from landslides along the Missouri River. Smoldering bluffs (Tour Map symbol 'B') were observed during the Lewis and Clark expedition of 1804 -1806. A telltale reddish coloration of oxidized shale is visible where the shale has burned. In addition, some small gypsum crystals (selenite form) can be found on the surface of the Pierre shale.
Lignite in the Hell Creek formation has also burned on many occasions as well. Generated heat fused the strata surrounding the lignite seam to resemble brick and form a material locally known as scoria. Its variegated light red to deep purple coloring is visible on the sides and tops of many buttes in this formation.
Rock hounds can collect small semiprecious stones (agates, chalcedony, and jasper) at a number of locations outside of the Badlands National Park (Tour Map symbol 'G') in the National Grassland. These semiprecious stones are found in bands of loose gravel that weathered out of the Badlands strata.
Sheepherders in open range country piled loose rocks in cairns (locally called stone johnnies) on hilltops to bide their time and mark their territory. Even though they seldom exceed 2m in height, they are visible from great distances because of their prominent positions on the landscape.
The sand hills of Nebraska extend into southwestern South Dakota in Todd and Bennett counties (Tour Map symbol 'D'). These hills are wind blown deposits of coarse-grained materials of varying heights. Hillsides that lack vegetation on which wind erosion is actively occurring are called 'blowouts'.
