Badlands

Barren, scoured and eroded by water and etched by weathering and wind-driven sand and rain, badlands are dramatic landforms that develop an intricate network of deeply incised, narrow, winding gullies and occasional fantastically shaped hoodoo rocks.

Steep, often precipitous and densely rilled slopes almost devoid of vegetation are striking evidence of the forces of erosion. To European settlers, such areas were clearly worthless. Perhaps the term badlands is derived from the French terres mauvais à traverser, meaning "land hard to cross," as the French were among the earliest explorers in the interior of western North America.

Distribution

Areas of badlands occur at scattered locations throughout the prairies of western Canada, where they stand in stark contrast to the gently rolling landscape of the plains. Badlands are particularly prevalent along the river valleys of southern Alberta, especially along the Red Deer River, where they flank the river for 300 km and culminate in their most impressive display in Dinosaur Provincial Park and are associated with the world-famous dinosaur fossils. The park was designated a United Nations World Heritage Site in 1979 partly on the basis of its spectacular badlands, the largest in Canada.

Badlands form where weak, relatively unconsolidated sedimentary rocks such as shale, siltstone and poorly cemented sandstone are exposed to vigorous erosion processes. They tend to occur in arid or semiarid regions such as southern Alberta, where rain often falls in short, torrential convectional storms.

Erosion

Rapid runoff on the barren, relatively impermeable, clay-rich rocks quickly cuts rills and gullies, producing rates of erosion of several mm a year. Surface erosion is often accompanied by extensive fracture-controlled subsurface piping or tunnel erosion, which frequently leads to the formation of sinkholes and slope failure.

Many of the badlands areas of Alberta were initially formed as a result of rapid channel downcutting by glacial meltwater during the retreat of the Late Wisconsin Laurentide ice sheet about 14 000 years ago. The steep valley walls, cut into the soft Upper Cretaceous rocks that dominate the bedrock geology of southern Alberta, were ideal for the development of badlands.