What are dunes primarily formed from?

Dunes are primarily formed from sand accumulating due to wind obstruction. This natural process occurs when the wind carries sand particles and deposits them in areas where obstacles, such as vegetation, rocks, or other dunes, slow down the wind's speed. As the wind loses energy, it can no longer carry the heavier sand grains, leading to their accumulation and the formation of dunes. Over time, these dunes can grow in size and change shape depending on the prevailing wind patterns and the availability of sand.

The other options refer to different geological processes: water erosion involves the wearing away of land by water, glacial movement pertains to the actions of glaciers creating landforms, and rock disintegration refers to the breakdown of rock into smaller pieces due to weathering processes. While each of these processes contributes to the overall landscape, they do not play a role in the formation of dunes.