Landscape Evolution in Arid Climates

Steven Dutch, Professor Emeritus, Natural and Applied Sciences, University of Wisconsin - Green Bay

The picture here shows the evolution of landscapes in arid climates.

The top left diagram shows the youthful stage. Rivers are deepening their valleys but there is flat land between the valleys because small streams have not yet had time to erode deep channels. The river valleys are steep sided and V-shaped.
The top right diagram shows the beginnings of the mature stage. Slopes stay steep but retreat. Unlike humid climates, there is little chemical weathering or soil creep to round off the landscape. Where small streams enter the main valleys, they dump cones of debris called alluvial fans.
The lower left diagram shows the later part of the mature stage. As slopes continue to retreat, they leave behind a gently sloping rock surface called a pediment.
The lower right diagram shows the old age stage. Slopes have retreated so far that the mountains begin to break up into isolated small highlands called inselbergs (German for "island mountain"). Pediments from opposite sides of the mountains meet to create a pediment pass. Water flowing into basins never accumulates deeply enough to carve an outlet. Instead the water ponds up in low spots and evaporates, leaving deposits of dissolved minerals behind. These small, usually very salty ponds are called playa lakes. Theoretically, erosion could continue until the landscape consists of nothing but pediment surfaces, a state called a pediplain. Parts of the Sahara or the Outback of Australia come close to this condition.

Possible Coloring

Created 27 February 2008, Last Update 15 January 2020