How are coastal dunes primarily formed?

Coastal dunes are primarily formed from the deposition of sand by wind, which is the correct answer. This process begins when loose sand is made available through erosion of beaches or from other sediment sources. When the wind blows across the beach and inland areas, it picks up fine sand particles and carries them. As the wind velocity decreases, these particles are deposited, leading to the formation of dunes.

The shape and size of the dunes can vary significantly based on factors such as wind direction, speed, and the availability of sand. Vegetation can also play a crucial role in stabilizing these dunes and preventing erosion, as plant roots help to hold the sand in place. Over time, dunes can grow in size and change shape as sandy deposits are moved around by shifting winds.

The other options do not accurately represent the primary mechanism behind coastal dune formation. While erosion from storm waves can contribute to the availability of beach sand, it is not the main process responsible for dune creation. Human construction may alter existing dunes or create artificial structures but does not lead to the natural formation of dunes. Lastly, volcanic activity is unrelated to coastal dune formation, as it pertains to the eruption of magma and the creation of landforms that are distinct from those formed by wind actions in