What are sand dunes?

• A. Mounds of sand formed by the wind's action, often found in deserts and along coastlines.
• B. A large rock formation.
• C. A shallow tidal pool.
• D. Volcanic rock layers cooling and solidifying.

Answer: (A)

Wind-driven sand forms mounded ridges called sand dunes. They develop when loose sand is picked up by the wind and deposited where the wind slows or is obstructed, gradually building up a pile that can grow into a dune. Dunes commonly appear in deserts and along coastlines where there is plenty of sand and little vegetation to hold it in place. The shape and size depend on wind direction and strength, how much sand is available, moisture, and vegetation. They’re not rock formations, tidal pools, or volcanic rock layers—the latter features involve solid rock, water, or cooling lava, respectively.