With little rain, wind plays a major role in eroding desert landscapes.
As the wind swoops down across the planet, it shifts bits of earth from one place to another. In its course, it builds up formations like sand dunes and eats away at the Earth's surface, creating hollows. The activities of the wind, called eolian processes (which include deflation), particularly affect arid regions where the scarcity of plant roots renders the loose soil subject to the eroding aspects of the wind.
Deflation
A type of eolian erosion, deflation results as the wind removes and transports fine-grained particles from an area. Deflation commonly occurs in desert regions where little water and vegetation exist to weigh down the soil. Consequences of the deflation process include wearing desert areas flat or carving hollows into the sand.
Blowouts
As the wind blows away fine desert sand, it often reveals depressions in the ground beneath the sand. These depressions, or blowouts, form irregular or symmetric shapes and range in size from shallow to deep, from a few feet wide to multiple miles. The closed bottom of a blowout can collect runoff or cross groundwater.
Deflation in semi-arid deserts with a little vegetation forms hollows called pans in sand sheets that hold water, according to the U.S. Army Corp of Engineers. In regions with semi-vegetated sand dunes, hollows or blowouts usually become source areas for parabolic dunes or dunes that form with a depression between tips. In addition, blowouts occurring around plant roots and rock structures clear out all loose sand around the base, forming a column out of the plant or rock.
Desert Pavement
Another consequence of the eolian process of deflation, desert pavement results when the wind carries away fine particles, revealing a flat sheet-like rock surface. While the size of particle removed depends on the strength of the wind, over time, both fine sand particles and larger ones are carried away. Eventually the land surface loses elevation, sinking down until only a tightly packed layer of pebbles and rocks, called pavement, remains, too heavy for the wind to lift away. The wind continues to batter these pebbles and rocks, further smoothing and polishing them down.
While sand dunes may portray the face of desert regions, they can only claim 20 percent of the landscape. Features like desert pavement, however, according to the U.S. Geological Survey, compose nearly half of all desert regions.
Rock Varnish
In addition to carving hollows in the earth and smoothing desert areas into flat pavement surfaces, deflation also exposes rocks once hidden beneath sand. If exposed for a long period of time to the elements, these rocks form rock varnish, or dark, shiny stains, on the exposed surfaces. Certain minerals and compounds like manganese, hydroxides and clay minerals, in particular, create the most shine and varnishes.
Tags: desert regions, sand dunes, away fine, beneath sand, carving hollows, desert areas, pebbles rocks
