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Dune fields in the Australian desert. Sand dunes of the Empty Quarter to the east of Liwa Oasis, United Arab Emirates. A dune is a landform composed of wind- or water-driven sand.
Issaouane Erg, Algeria Linear Dunes, Namib Sand Sea. An erg (also sand sea or dune sea, or sand sheet if it lacks dunes) is a broad, flat area of desert covered with wind-swept sand with little or no vegetative cover. [1] The word is derived from the Arabic word ʿirq (عرق), meaning "dune field". [2]
As barchan dunes migrate, smaller dunes outpace larger dunes, catching-up the rear of the larger dune and eventually appear to punch through the large dune to appear on the other side. The process appears superficially similar to waves of light, sound, or water that pass directly through each other, but the detailed mechanism is very different.
Gully – Landform created by running water and/or mass movement eroding sharply into soil; Hill – Landform that extends above the surrounding terrain; Hillock, also known as Knoll – Small hill; Mesa – Elevated area of land with a flat top and sides, usually much wider than buttes; Mountain pass – Route through a mountain range or over ...
Star dunes are formed by variable winds, and have several ridges and slip faces radiating from a central point. They tend to grow vertically; they can reach a height of 500 m (1,600 ft), making them the tallest type of dune. Rounded mounds of sand without a slip face are the rare dome dunes, found on the upwind edges of sand seas. [59]
Ridge and swale, or in dunal areas dune and swale, is a landform consisting of regular, parallel ridges alternating with marshy depressions. [1] Ridge-and-swale landscapes are most commonly formed by the gradual movement of a beach , for example as a result of gradually fluctuating water levels, or the shifting meanders of a river.
A landform is a natural or anthropogenic [1] [2] land feature on the solid surface of the Earth or other planetary body. Landforms together make up a given terrain , and their arrangement in the landscape is known as topography .
The topography of an area may refer to the landforms and features themselves, or a description or depiction in maps. Topography is a field of geoscience and planetary science and is concerned with local detail in general, including not only relief, but also natural, artificial, and cultural features such as roads, land boundaries, and buildings ...