How Do Sand Dunes Move?
Sand can only be moved by strong, steady winds. The air must be moving at least 15 miles per hour to be able to pick up sand grains. In the Tularosa basin, it is primarily between February and April that the winds are strong enough. These winds are called unidirectional winds because they always move in the same direction, from the southwest to the northeast. As the wind blows, it pushes the sand ahead of it, so individual dunes are slowly moving to the northeast. Sand is not as easy to move as you might think. Even very strong winds can’t lift the sand any higher than three feet above the ground. As the wind blows, it lifts small sand grains a few feet off the ground, then drops them. When they hit the ground, they bump into other sand grains and cause them to jump up and be caught by the wind. It’s almost as if the sand is playing leap-frog, jumping and bumping along. This kind of jumping movement is called saltation. You can see this kind of movement on the windward side of the dune
