Aeolian Transport (English)
Transport éolien (Français)
This article was written by students in a grade school class in Australia.
Aeolian processes, in the study of geology and weather, pertain to wind activity and specifically to the wind's ability to shape the surface of the Earth. Winds may erode, transport, and deposit materials, and are effective agents in regions with sparse vegetation and a large supply of unconsolidated sediments.
Aeolian Transport is the first process of coastal dune formation and involves the movement and weathering of sand particles behind and parallel to the shoreline.
There are three main processes involved in Aeolian Transport:
- Suspension - The finer sand particles are moved by the wind, high in the air. They are not affected by gravity and therefore can travel thousands of kilometres before they land on earth again. When they land, it is often because they have combined with raindrops and fall with the rain.
- Saltation (The most common form of sand transport) - When the wind hits the ground, it causes turbulence, disturbing the sand particles. If the wind has enough velocity, it will cause the particles to start moving (initially just along the ground). The required velocity is called critical velocity and varies depending on grain size, vegetation present and the moisture levels of the sand (which holds the sand down, requiring the critical velocity to be greater). As the sand moves, it hits other grains which cause them to bounce up in the air. The wind then picks these airborne particles up and carries them. Gravity causes them to fall back down. If sand lands on a hard surface (e.g., rock), the sand particle will bounce off again, being carried further. If it lands on a sandy surface, it will cause other particles to be disturbed, bounce up and they too will be carried, thus starting off a chain reaction.
- Surface creep - The larger particles are too heavy to be picked up and carried by the wind so instead, they move along the ground. When they become dislodged by the falling ones, they roll along the ground. Through this process, they are not only moved but by moving against other particles, they erode into smaller particles which can be moved by saltation or suspension.