Longitudinal dune
Also called: Linear dune · Topic: Landforms and their Evolution: Rivers, Groundwater, Glaciers, Waves and Wind · NCERT: Class 11, Ch 2 "Structure and Physiography"; Class 11, Ch 6 "Landforms and their Evolution"
Meaning
A longitudinal dune is a long, low ridge of sand that lies parallel to the main wind direction. It forms where there is not much sand and the wind blows steadily from one direction. These dunes can stretch a long way across a desert. Their direction tells you the direction of the main wind.
Example
The Thar desert in western Rajasthan has longitudinal dunes, especially in its drier western parts. Barchans (crescent-shaped dunes) are also found there.
Don't confuse with
- Transverse dune: lies at right angles to the wind, not parallel to it.
- Seif: a barchan with only one wing, formed when the wind changes direction. A longitudinal dune forms under a steady wind.