Question

What are different types of sand dunes?

Answer 1

Hint: A dune is a sand mound created by the wind, typically on a beach or in the desert. Wind blows sand into a sheltered area behind an obstacle, forming dunes. As sand grains collect, dunes form. There is a windward side and a slip face on every dune.

Complete answer:
Even though sand dunes come in all shapes and sizes, scientists still lump them together into broad categories. The United States Geological Survey (USGS) has defined five forms of sand dunes based on satellite and aerial imagery of the world's deserts:
a) Linear dune: The linear dune is straighter than the crescentic dune and has prominent ridges. Linear dunes, unlike crescentic dunes, are longer than they are large, with some measuring more than 100 miles (160 kilometres) in length. These dunes typically occur in parallel sets separated by other sand, gravel, or rocky corridors, and the ridges are long and snakelike.
b) Crescentic dune: The most common form of sand dune is the crescentic dune, also known as the barchan dune. This dune is shaped like a crescent moon with points at each end, and it is normally wider than it is tall, as the name implies. When winds blow in one direction, crescent dunes form. This form of dune can cross desert surfaces faster than any other. China's migratory dunes are crescentic dunes.
c) Dome dune: The dome dune is unusual, oval or circular in shape, and does not have a slip face. At the ends of crescentic dunes, dome dunes can be found. The majority of dome dunes are low, standing just a few feet tall.
d) Star dune: The star dune gets its name from the arms that radiate out from a central pyramid-shaped mound. Multidirectional winds cause star dunes to expand upward rather than outward. They're common in the Sahara Desert, and they usually appear near topographic barriers. Some star dunes in China are more than 1,600 feet (500 metres) tall, making them among the world's tallest sand dunes.
e)Parabolic dune: The parabolic dune is U-shaped, but it varies from the crescentic dune in that its crests point upward, with elongated arms trailing behind. The trailing arms of a parabolic dune are normally anchored by vegetation. The trailing arm of the world's longest known parabolic dune is nearly 7.5 miles (12 kilometres) long.

Note: A dune is a hill of loose sand formed by aeolian processes (wind) or the flow of water in physical geography. Dunes come in a variety of shapes and sizes, depending on how they deal with the movement of air or water. Dunes can be found in deserts and along coastlines. They can be found in deserts, on beaches, and even on degraded and abandoned farm fields in semiarid regions like northwest India and parts of the southwestern United States, where loose sand is windblown.