Yardangs in Dasht-e Lut, Iran

Rain, wind and ice constantly wear down the Earth's land surface and transport the resulting broken down rock and soil to the oceans in a process called erosion.

Left unchecked, erosion would transport all the Earth's dry land into the oceans, leaving a water world. It is only the movement of the Earth's plates, which builds mountains, that stops this happening.

Geologists are quite precise about what erosion is: The term erosion only covers the transportation of Earth materials. Rock and soil are altered while still in place by a process referred to as weathering. Weathering often makes rock and soil susceptible to erosion.

Image: The wind eroded ridges in this image are known as yardangs. These examples are in the Dasht-e Lut desert, Iran. (credit: George Steinmetz/SPL)


Yardangs in Dasht-e Lut, Iran Erosion

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While erosion is a natural process, human activities have increased by 10-40 times the rate at which erosion is occurring globally. Excessive (or accelerated) erosion causes both 'on-site' and 'off-site' problems. On-site impacts include decreases in agricultural productivity and (on natural landscapes) ecological collapse, both because of loss of the nutrient-rich upper soil layers. In some cases, the eventual end result is desertification. Off-site effects include sedimentation of waterways and eutrophication of water bodies, as well as sediment-related damage to roads and houses. Water and wind erosion are the two primary causes of land degradation; combined, they are responsible for about 84% of the global extent of degraded land, making excessive erosion one of the most significant environmental problems world-wide.


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