Did the wind ever blow your hat away? Did you ever drop your notebook on a windy day? How many important pages did you lose? Wind is moving air. It can pick up light materials and carry them far away.
Wind is a force of erosion(仗蚀). It can carry away small
martials such as dust particles(灰尘微粒) and sand particles from the earth's surface. However, wind itself does not cause much erosion. Most "wind" erosion is done by particles which are cried by wind. Wind is an important natural force of erosion in dry places.
Wind can easily pick up sand particles. When they are blown against rocks, the sand particles hit the rocks in the wind. This happens over and over again. Little by lite, the rocks wear down.
The particles which are carried by wind not only cause erosion, they also build up. What is carried away by the wind in one place will drop somewhere else.
When wind slows down, it drops the materials that it is carrying. When sand is dropped, it builds up and becomes dunes(沙丘). Sand dunes are common in deserts and on beaches. Some dunes can be harmful. They can bury(埋) farms and homes, even whole towns.
Wind carries dust particles higher and farther than it carries sand. Thick deposits of wind-blown dust may also build up. The wind-blown dust is called loess(黄土). Loess deposits are found in Washington State and Oregon State.
Sometimes people plant grasses and trees to try to stop wind erosion. How does this help? The roots of plants help to hold down soil and other particles found on the ground.
