DESERT , a
See also:term somewhat loosely employed to describe those parts of the
See also:surface of the
See also:earth which do not produce sufficient vegetation to support a human population . Few areas of large extent in any
See also:part of the
See also:world are absolutely devoid of vegetation, and the transition from typical desert conditions is often very gradual and
See also:ill-defined . (" Desert " comes from
See also:Lat. deserere, to abandon; distinguish " desert," merit, and " dessert," fruit eaten after
See also:dinner, from de and servier, to serve.) Deserts are conveniently divided into two classes according to the causes which give rise to the desert conditions . In "
See also:cold deserts " the want of vegetation is wholly due to the prevailing low temperature, while in " hot deserts " the surface is ur productive because, on account of high temperature and deficient rainfall, evaporation is largely in excess of precipitation . Cold deserts accordingly occur in high latitudes (see TUNDRA and POLAR REGIONS) . Hot desert conditions are primarily found along the tropical belts of high atmospheric pressure in which the conditions of warmth and dryness are most fully realized, and on their.
See also:equatorial sides, but the zonal arrangement is considerably modified in some regions by the monsoonal influence of elevated land . Thus we have in the
See also:northern hemisphere the
See also:Sahara desert, the deserts of
See also:Iran, Turan, Takla Makan and
See also:Gobi, and the desert regions of the
See also:Basin in
See also:America; and in the
See also:southern hemisphere the
See also:Kalahari desert in Africa, the desert of
See also:Australia, and the desert of Atacama in South America . Where the
See also:line of elevated land runs east and west, as in
See also:Asia, the desert
See also:belt tends to be displaced into higher latitudes, and where the line runs north and south, as in Africa, America and Australia, the desert zone is cut through on the windward side of the
See also:elevation and the arid conditions intensified on the
See also:lee side . Desert conditions also arise from
See also:local causes, as in the case of the
See also:Indian desert situated in a region inaccessible to either of the two
See also:main branches of the south-west monsoon . Although
See also:rivers rising in more favoured regions may
See also:traverse deserts on their way to the
See also:sea, as in the case of the Nile and the
See also:Colorado, the fundamental
See also:condition of an arid
See also:area is that it contributes nothing to the
See also:waters of the ocean . The
See also:rain-fall chiefly occurs in violent cloudbursts, and the soluble
See also:matter in the
See also:soil is carried down by intermittent streams to
See also:salt lakes around which deposits are formed as evaporation takes place . The land forms of a desert are exceedingly characteristic .
Surface erosion is chiefly due to rapid changes of temperature through a wide range, and to the
See also:action of
See also:wind transferring sand and dust, often in the
See also:form of "
See also:dunes " resembling the waves of the sea . Dry valleys, narrow and of great
See also:depth, with precipitous sides, and ending in " cirques," are probably formed by the intense action of the occasional
See also:cloud-bursts . When
See also:water can be obtained and distributed over an arid region by irrigation, the surface as a
See also:rule becomes extremely productive . Natural springs give rise to oases at intervals and make the
See also:crossing of large deserts possible . Where a
See also:river crosses a desert at a level near that of the general surface, irrigation can be carried on with extremely profitable results, as has been done in the valley of the Nile and in parts of the Great Basin of North America; in cases, however, where the river has cut deeply and flows far below the general surface, irrigation is too expensive . Much has been done in parts of Australia by means of artesian
See also:wells . For a general account of deserts see
See also:Professor Johannes
See also:Walther, Das Gesetz der Wuslenbildung (Berlin, 1900), in which many references to other
See also:original authorities will be found . (H . N .
There are no comments yet for this article.
Do not copy, download, transfer, or otherwise replicate the site content in whole or in part.
Links to articles and home page are encouraged.