Final answer:
A star dune is the type of dune with three arms and resembles spiraled dunes, formed by winds blowing from multiple directions. This differentiates it from other dune types like transverse, parabolic, and longitudinal dunes.
Step-by-step explanation:
The type of dune described in the question, that has three arms and can resemble two spiraled dunes, is known as the star dune. These dunes form in areas where wind direction changes frequently, and the sediments are carried in various directions, creating a star-like pattern with multiple ridges and slip faces. Star dunes can grow to be very high and remain stationary despite the shifting winds because they tend to accumulate more sand. When compared to star dunes, transverse dunes are aligned perpendicularly to the prevailing wind, often forming in areas with a constant wind direction and abundant sand. Parabolic dunes have a U-shaped appear with the tips pointing upwind, often stabilized by vegetation. Longitudinal dunes, also known as seif dunes, form parallel to the prevailing wind when sand supply is limited.
It is worth noting that there are two types of dunes: subaerial and subaqueous. Subaerial dunes are familiar, wind-blown sand structures commonly seen in deserts and on beaches and can be vegetated. On the other hand, subaqueous dunes, known as sandwaves, form under water bodies such as rivers, estuaries, and on the continental shelf.