When the soil is dry, it easily turns to dust, and the wind can pick up the soil particles and carry them away. On an island, this dust is usually carried out to sea where it is lost. The rain falling on the bare soil also loosens it, making mud or muddy water that runs off the land, carrying the soil away. The running water itself is no longer slowed by plants, and cuts into the land, making ravines and gullies. In extreme cases all the soil can be washed away, leaving bare rock, but more often only a little layer is lost each year, and people do not realize that their good land is disappearing.
Erosion can occur even on flat land, but it is made much worse when the land is sloping.
The steeper the slope, the greater the danger of serious erosion, and the more difficult it is to apply effective control measures. A little erosion is natural and normal, but it is usually very slow and the soil lost is replaced by the new soil that is slowly but constantly being made. When the natural plant cover is damaged or the land is developed, erosion goes much faster and this balance is lost. Erosion not only damages the land, it hurts other resources as well. Certain kinds of tropical soils are also subject to laterization.