Badlands Of The United States

Badlands are a type of dry terrain where softer sedimentary rocks and clay-rich soils have been extensively eroded."Badlands" in ''Chambers's Encyclopædia''. London: George Newnes, 1961, Vol. 2, p. 47. They are characterized by steep slopes, minimal vegetation, lack of a substantial regolith, and high drainage density.A.J. Parsons and A.D. Abrahams, Editors (2009) ''Geomorphology of Desert Environments'' (2nd ed.) Springer Science & Business Media Ravines, gullies, buttes, hoodoos and other such geologic forms are common in badlands.

Badlands are found on every continent except Antarctica, being most common where there are unconsolidated sediments. They are often difficult to navigate by foot, and are unsuitable for agriculture. Most are a result of natural processes, but destruction of vegetation by overgrazing or pollution can produce anthropogenic badlands.

Badlands topography

Badlands are characterized by a distinctive badlands topography. This is terrain in which water erosion has cut a very large number of deep drainage channels, separated by short, steep ridges ('' interfluves''). Such a drainage system is said to have a very fine drainage texture, as measured by its ''drainage density''. Drainage density is defined as the total length of drainage channels per unit area of land surface. Badlands have a very high drainage density of 77 to 747 miles per square mile (48 to 464 kilometers per square kilometer). The numerous deep drainage channels and high interfluves creates a stark landscape of hills, gullies, and ravines.

In addition to a dense system of drainages and interfluves, badlands often contain buttes and hoodoos ("mushroom rocks"). These are formed by resistant beds of sandstone, which form the caprock of the buttes and hoodoos.

Origin

Badlands arise from a combination of an impermeable but easily eroded ground surface, sparse vegetation, and infrequent but heavy rainfall. The surface bedrock is typically mudrock, sometimes with evaporites, with only occasional beds of more resistant sandstone. Infrequent heavy rains lead to heavy erosional dissection. Where sudden precipitation cannot penetrate impermeable clays, it is channeled into a very dense system of streamlets that erode a dense system of ever-enlarging, coalescing gulleys and ravines. Erosion is enhanced by pelting raindrops that dislodge soft sediments. The presence of bentonite clay further increases erodability, as can rejuvenation of the drainage system from regional uplift, as occurred at Badlands National Park.

In addition to surface erosion, badlands sometimes have well-developed ''piping'', which is a system of pipes, joints, caverns, and other connected void spaces in the subsurface through which water can drain. However, this is not a universal feature of badlands. For example, the Henry Mountains badlands show very little piping.

The precise processes by which the erosion responses take place vary depending on the precise interbedding of the sedimentary material. However, it has been estimated that the badlands of Badlands National Park erode at the relatively high rate of about per year. The White River draining Badlands National Park was so named for its heavy load of bentonite clay eroded from the badlands.

Regolith

Badlands are partially characterized by their thin to nonexistent regolith layers. The regolith profiles of badlands in arid climates are likely to resemble one another. In these regions, the upper layer (~) is typically composed of silt, shale, and sand (a byproduct of the weathered shale). This layer can form either a compact crust or a looser, more irregular aggregation of "popcorn" fragments. Located beneath the top layer is a sublayer (~), below which can be found a transitional shard layer (~), formed largely of loose disaggregated shale chips, which in turn eventually gives way to a layer of unweathered shale. Badlands such as those found in the Mancos Shale, the Brule Formation, the Chadron Formation, and the Dinosaur Provincial Park can be generally said to fit this profile.

In less arid regions, the regolith profile can vary considerably. Some badlands have no regolith layer whatsoever, capping instead in bare rock such as sandstone. Others have a regolith with a clay veneer, and still others have a biological crust of algae or lichen

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