Wind erosion: how does dust get into the air?
Wind erosion occurs when wind blows hard enough upon the soil surface to move soil particles (Dust Watch Website). The process of wind erosion is fairly simple. Once set in motion by the force of the wind, a soil particle moves in a manner according to its size. Larger soil particles "creep" along the surface, medium-sized particles "hop" along the surface in a process called saltation, and small enough particles are suspended in the air and carried long distances as dust (Dust Watch Website). The diagram below depicts how the different types of wind erosion occur.
(Picture Courtesy of Dust Watch Website)
Water erosion: dirt never stood a chance
Water erosion is caused by the kinetic energy of rain fall on the soil surface and by the mechanical force of runoff (Hong Kong University Website). Water erosion is a powerful force, one that has the potential to carve out massive gullies and even canyons over long periods of time.
(Picture courtesy of the Australian Department of Agriculture)
Water erosion can be further classified into three different types. The first is splash erosion, which is the detachment and airborne movement of small soil particles by the impact of raindrops on the soil. The second is sheet erosion, a type of erosion that results in heavy rain on bare soil where water flows as a sheet down any gradient carry soil particles. The third type is gullying, where water flowing down creeks and waterways widens them and carries soil downstream. By far, the most water erosion takes place during floods when very large sediment loads move farther and faster than any other type of water erosion. Rill erosion is the removal of soil by concentrated water running through little streamlets(Purdue University Website).
Gravity erosion: Newton's Laws in action
Gravity erosion occurs when soil moves under the influence of gravity. This usually happens on steep slopes and hillsides. Basically, the process involves the movement of soil from higher to lower grounds due to self weight (Hong Kong University Website).
(Picture courtesy of Hong Kong University Website)
Gravity erosion is a fairly straightforward concept; gravity simply pushes soil down a slope. It can happen at a fast or slow pace, but in certain cases gravity erosion can cause a landslide, which is a massive, rapid movement of soil and sediment due to gravity (Soil: Erosion and Conservation Website). Gravity erosion happens on a much smaller scale compared to wind and water erosion, but remains a significant factor in certain geographical locations.
There is no question that soil erosion is a natural process, but it becomes unnatural when human activity speeds up the process to dangerous levels. To find out what the human causes of soil erosion and degradation are, go to the next page!