Today we want to learn how our weather has built up or worn down the earth's surface to form mountains, valleys, deserts, plains, soil, lakes, and rivers. We usually think of rocks as being hard, solid, and unchanging. But various forces are always at work on the earth's surface, breaking up rocks and wearing them away. Rocks are formed deep in the earth or under water. As soon as the rocks are exposed, the weather begins to destroy them.
Weather is the term used to describe the changing state of the atmosphere.
Weather conditions such as sunshine, rain, snow, sleet, or hail cause changes in land forms and rocks. Weathering is a process by which rocks are changed due to exposure to the weather. Some of these changes are chemical changes while others are physical changes. Chemical weathering causes chemical changes in the minerals of a rock. It usually proceeds more rapidly in warm, moist climates.