The correct option is 1 and 3 only.
Explanation
Wind acts as a significant exogenic agent, particularly in arid and semi-arid regions. Its ability to erode, transport, and deposit material is governed by its kinetic energy, which is a function of wind velocity and the nature of the particles.
Statement 1 is Correct
Wind is considered a good sorting agent. As wind transports materials, it separates particles based on their size and weight. Heavier particles are moved via surface creep, medium particles via saltation, and fine dust via suspension. Consequently, wind deposits (such as loess or dune sands) are typically uniform in grain size (well-sorted), unlike glacial deposits which are unsorted.
Statement 2 is Incorrect
The sorting of grains is directly dependent on the velocity of the wind. The competence of the wind (the maximum size of particle it can transport) increases with velocity. As wind velocity decreases, it loses the energy required to carry heavier particles, causing them to settle first, followed by lighter particles. This relationship between velocity and particle size is the fundamental mechanism of sorting.
Statement 3 is Correct
The development of depositional features in arid regions primarily requires a sufficient supply of sand and a constant wind to transport it. While obstructions (like rocks or vegetation) often serve as the immediate trigger for accumulation by checking wind speed, the presence of sand and wind are the prerequisite conditions that allow these features to develop across desert landscapes.
Key Takeaway
Aeolian (wind) deposits are characterized by being well-sorted. This sorting is strictly controlled by wind velocity, which determines the size of the load the wind can carry or deposit at any given moment.