Tuesday, June 11, 2019

How the desert was formed

A desert is a barren area of landscape where little precipitation occurs and, consequently, living conditions are hostile for plant and animal life. The lack of vegetation exposes the unprotected surface of the ground to the processes of denudation. About one-third of the land surface of the world is arid or semi-arid. This includes much of the polar regions where little precipitation occurs and which are sometimes called polar deserts or "cold deserts". Deserts can be classified by the amount of precipitation that falls, by the temperature that prevails, by the causes of desertification or by their geographical location.


Deserts are formed by weathering processes as large variations in temperature between day and night put strains on the rocks which consequently break in pieces. Although rain seldom occurs in deserts, there are occasional downpours that can result in flash floods. Rain falling on hot rocks can cause them to shatter and the resulting fragments and rubble strewn over the desert floor are further eroded by the wind. This picks up particles of sand and dust and wafts them aloft in sand or dust storms. Wind-blown sand grains striking any solid object in their path can abrade the surface. Rocks are smoothed down, and the wind sorts sand into uniform deposits. The grains end up as level sheets of sand or are piled high in billowing sand dunes. Other deserts are flat, stony plains where all the fine material has been blown away and the surface consists of a mosaic of smooth stones. These areas are known as desert pavements and little further erosion takes place. Other desert features include rock outcrops, exposed bedrock, and clays once deposited by flowing water. Temporary lakes may form and salt pans may be left when waters evaporate.


Plants and animals living in the desert need special adaptations to survive in the harsh environment. Plants tend to be tough and wiry with small or no leaves, water-resistant cuticles and often spines to deter herbivory. Some annual plants germinate, bloom and die in the course of a few weeks after rainfall while other long-lived plants survive for years and have deep root systems able to tap underground moisture. Some animals remain in a state of dormancy for long periods, ready to become active again during the rare rainfall.


People have struggled to live in deserts and the surrounding semi-arid lands for millennia. The cultivation of semi-arid regions encourages erosion of soil and is one of the causes of increased desertification. However, Many trade routes have been forged across deserts, especially across the Sahara Desert, and traditionally were used by caravans of camels carrying salt, gold, ivory, and other goods and Some mineral extraction also takes place in deserts, and the uninterrupted sunlight gives the potential for the capture of large quantities of solar energy.


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Erg Chebbi Dunes, Merzouga, Moroccan Sahara in 4K (Ultra HD)

The Erg Chebbi Dunes in the Saharan desert, near Merzouga, Morocco. The Dunes at Sunrise and some views around Merzouga.