Grain erosion ― an intense form of rock erosion

Grain erosion is defined as the phenomenon of physically breaking down bare rocks. Bare rocks are caused by avalanches, landslides and human activities. Grain erosion causes flying stones that can injure humans, and results in numerous slope debris flows. The process of grain erosion is studied by field investigations and experiments. The rocks are broken down to grains under the action of insolation and temperature change. Then, wind detaches the grains from the bare rock, the grains flow downslope under the action of gravity, and the grains accumulate at the toe of the hillslope forming a depositional fan. The most serious grain erosion occurs in spring and early summer when it is very hot and dry. Experimental results showed that the number of grains blown by wind, per area of rock surface per unit time, is proportional to the fourth power of the wind speed; however, the size of the grains increases linearly with the wind speed.