Landscape Evolution in Arid Climates
Steven Dutch, Natural and Applied Sciences, University
of Wisconsin - Green Bay
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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
- 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
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Created 27 February 2008, Last Update
25 May 2011
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