Large smooth elongated windblown deposits that extend parallel to the prevailing wind are known as what?

The term for large, smooth, elongated deposits formed by the wind that run parallel to the prevailing wind direction is whalebacks. Whalebacks are characteristic landforms created in arid and semi-arid environments where wind erosion and deposition take place. These formations typically exhibit a streamlined shape, similar to that of a whale's back, which is the origin of their name.

Dunes, in contrast, are mounds or ridges of sand accumulated by wind and are often characterized by a more complex structure, including ripples and shifting patterns. Loess refers to a type of sediment formed from wind-blown silt, creating extensive deposits but not necessarily in the smooth, elongated shape of whalebacks. Sandbars are formed by the accumulation of sediment in water bodies, typically found in rivers and coastal areas, serving a different purpose and originating from water currents rather than wind.

Understanding the characteristics and formation processes of these landforms clarifies why whalebacks are the correct answer, as they specifically relate to the conditions of wind-driven deposition.