A desert surface covered by sand is generally referred to as a sand sea, erg, or sand dune field.
While "desert" broadly describes arid regions, the specific term depends on the dominant landform. Not all deserts are sandy; in fact, only about 20% of the world's deserts are covered in sand. However, when sand is the primary surface feature, it can create distinctive landscapes.
Here's a breakdown of common terms:
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Sand Sea (Erg): This term usually denotes a vast, relatively flat area covered with sand. "Erg" comes from the Arabic word for dune field. Examples include the Sahara's Grand Erg Oriental and the Rub' al Khali (Empty Quarter).
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Sand Dune Field: This refers to an area dominated by sand dunes, which are wind-sculpted accumulations of sand. These fields can range in size from a few dunes to extensive regions covering thousands of square kilometers.
The presence of sand in a desert environment allows for the formation of various dune types, including:
- Barchan Dunes: Crescent-shaped dunes with horns pointing downwind.
- Linear Dunes (Seif Dunes): Long, parallel dunes aligned with the prevailing wind direction.
- Star Dunes: Radially symmetrical dunes with multiple slipfaces.
- Transverse Dunes: Ridges perpendicular to the wind direction.
The composition of the sand itself can vary, depending on the source rock and the weathering processes involved. Sand can consist of quartz, gypsum, or even shell fragments.
In summary, while not all deserts are sandy, a desert surface primarily composed of sand is typically called a sand sea or erg, characterized by extensive sand sheets and/or dune fields.
