The arid areas of the world range between 0º and 60º north latitude and between 0º and 55º south latitude. Strictly arid modeling is limited to sub-desert systems (steppe areas, Mediterranean basin and northern Mexico, among others), desert and desert tropical areas, such as the Sahara, Kalahari, Arabia, Australian and the Sonoran desert.
The characteristic aspects or reliefs of this type of morphoclimatic system are the following, divided into different groups:
Cárcavas and ravines; erosion pedestals; mountains-island or isolated hills standing out in the plain; mushroom-shaped rocks; rocky arches produced by the action of wind loaded with fine particles; dry channels except in the wet season of heavy rains and calls uadis in Morocco, ravines in the Canary Islands, ramblas in the SE of Spain and you laugh in Catalonia; reg or stone fields (in the Sahara), called hamada in Sudan, which correspond to large areas of low slope covered by countless stones.
These are the only ones that continue once the wind has dragged the finest material in suspension. They usually present a kind of dark varnish produced by the continuous erosion of wind-blown sand.
There are several forms of deposit: glacis or accumulation of rock fragments detached from the reliefs of the mountain-islands; desert pavement (accumulation of small songs among the older ones of the reg during the sporadic rainy season); loess o accumulation of silt-sized particles; erg or sand-covered plains; dunes or accumulation of sand-sized particles or smaller where characteristics are formed ripples or ripples.
All these characteristic morphologies of the arid zones are the consequence of the combined actions explained in these pages:
• Physical or mechanical weathering, which is the physical breakdown of rocks into fragments, due to changes in temperature, humidity and biological activity.
• Chemical weathering, processes carried out by means of water or by gaseous agents of the atmosphere such as oxygen and carbon dioxide.
• Wind action or wind erosion. The wind forms structures such as the dunes, but also other spectacular forms, in the rocks of the regions where it acts with greater intensity.
|Erosion in Spain|