A sand dune probably conjures up images of a lifeless pile of sand. Sand dunes, on the other hand, are dynamic natural structures. They develop, change, and travel. Dunes are mountains of blown sand in deserts and coastal areas. (1) ........ . The type of dune is determined by the direction of the wind, the type of sand, and the amount of vegetation. Deserts and the coast are home to sand dunes. A dune can be tall as a skyscraper or as small as an anthill. Every sand dune is the result of the same process: wind-driven accumulation of sand. The sand will travel wherever the wind takes it once it has been picked up by it. Despite the fact the majority of sand dunes are made of the same material and formed in the same way, their way, their appearances can vary greatly. (2) ........ . The shapes of star dunes, parabolic dunes, and longitudinal dunes, as well as transverse dunes, give them their names.
A. Sand dunes can also be found on other planets like Mars, Venus, Titan and Saturn's moon.
B. Sand dunes can also be found on other planets like Mars, Venus, Titan and Saturn's moon.
B. Dunes are referred to by their shape or their position in relation to the wind.
C. Dunes have been forming since geological past.
D. Sand is carried by the wind and accumulates in the vicinity of obstacles to form ridges and mounds.