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Wind erosion
Geoindicator


Name: Wind erosion

BRIEF DESCRIPTION: The action of wind on exposed sediments and friable rock formations causes erosion (abrasion) and entrainment of sediment and soil particles [see dust storm magnitude, duration and frequency]. Eolian action also forms and shapes sand dunes, yardangs (streamlined bedrock hills) and other landforms. Subsurface deposits and roots are commonly exposed by wind erosion. Wind can also reduce vegetation cover in wadis and depressions, scattering the remains of vegetation in interfluves. Stone pavements may result from the deflation (removal) of fine material from the surface leaving a residue of coarse particles. Blowouts (erosional troughs and depressions) in coastal dune complexes [see dune formation and reactivation] are important indicators of changes in wind erosion. The potential for deflation is generally increased by shoreline erosion or washovers, vegetation die-back due to soil nutrient deficiency or to animal activity, and by human actions such as recreation and construction.

SIGNIFICANCE: Changes in wind-shaped surface morphology and vegetation cover that accompany desertification, drought, and aridification are important gauges of environmental change in arid lands. Wind erosion also affects large areas of croplands in arid and semi-arid regions, removing topsoil, seeds and nutrients.

HUMAN OR NATURAL CAUSE: Eolian erosion is a natural phenomenon, but the surfaces it acts upon may be made susceptible to active wind shaping and transport by human actions, especially those, such as cultivation and over-grazing, that result in the reduction of cover vegetation.

ENVIRONMENT WHERE APPLICABLE: arid and semi-arid lands

TYPES OF MONITORING SITES: Dune fields, coastlines, desert surfaces

SPATIAL SCALE: patch to landscape / mesoscale to regional

METHOD OF MEASUREMENT: Field observations, aided by airphotos and field surveys. Changes in vegetation cover can be monitored using historical records, sequential maps, air photos, satellite images, and by ground survey techniques.

FREQUENCY OF MEASUREMENT: Every 5-20 years

LIMITATIONS OF DATA AND MONITORING: The effect of wind erosion on different rock types and landforms (with contrasted aerodynamic shapes) varies, so that it is not easy to assess the degree of erosion of a complex landscape.

APPLICATIONS TO PAST AND FUTURE: Differential erosion by wind in the past may be detected through study of buried soil horizons developed on ancient erosional surfaces, which formed during dry (wind erosion) to wet (soil formation) climatic cycles.

POSSIBLE THRESHOLDS: Sediment erosion and transport takes place within a specific range of wind speeds, depending on grain size, degree of cementation and compaction, moisture content, and vegetation cover.

KEY REFERENCES:

Abrahams, A.D, & A.J. Parsons 1994. Geomorphology of desert environments . London: Chapman and Hall.

Cooke, R., A. Warren & A. Goudie 1993. Desert geomorphology . London: UCL Press.

Lancaster, N. 1996. Geoindicators from desert landforms. In Berger, A.R. & W.J.Iams (eds). Geoindicators: Assessing rapid environmental changes in earth systems. : 251-268. Rotterdam: A.A. Balkema.

OTHER SOURCES OF INFORMATION: Geological surveys, desert research institutes, IGA.

RELATED ENVIRONMENTAL AND GEOLOGICAL ISSUES: Degradation of agricultural land, desertification.

OVERALL ASSESSMENT: Wind erosion is a valuable indicator of environmental change in arid and semi-arid regions.

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