Ever wondered how desert stacks emerge, how huge archways appear out of the rock and how colourful stripes stretch along rocky ledges in the desert? All of these features are the result of wind erosion – the fancy term for which is Aeolian processes.
In the wide-open expanses of deserts, the sheer force of the wind can eat into softer types of rock, such as sandstone. Rock particles are removed and lifted up by the wind (a process known as deflation) and then, as the wind blusters through the arid landscape, its path governed by the rock formations that dominate the terrain, these particles act almost like sandpaper on the rocks and gradually transform them into the streamlined shapes that follow the wind’s path – a process known as abrasion.
Over time, this gradual erosion produces the incredible landforms we associate with the desert landscape, which are known as ‘yardangs’. The type of rock in an area greatly affects how the wind shapes it. Softer rock types are easily eroded, while harder rock is far more resistant and is more likely to be polished by the ferocity of the wind, resulting in smooth, buffed formations.
Softer rock is carved out by the wind, producing much more pronounced effects, while a mixture of both hard and soft rock types can produce incredible formations such as buttes and arches. Read also Coastal Erosion Facts!
How rock archways are formed
Rock layers – Different types of rock with diff erent properties form and shape the landscape in layers.
Overlying rock – The wind gradually erodes the layers of rock above the cracks.
Cracks deepen – As the wind rushes through the cracks they are gradually eroded away and begin to widen and deepen.
Rain and ice – Rainwater dissolves some of the soft rock’s chemical makeup, while water in small cracks freezes and weakens the rock.
Rockfalls – The weakened softer rock begins to crumble and eventually falls away, leaving an arch of more resistant rock.
Archways widen – Wind erosion continues to wear away at every surface of the exposed archway, constantly widening it.
Collapse – Eventually, the arch is eroded so much that it collapses, leaving two rock pillars standing either side.
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