The earth is always changing. Some of the changes are caused by the wwather. For example,in a desert, the wind blows the sand around. It makes the desert look differnt every year. Rain also causes changes. It washes away the dirt and even changes the shape of some rocks. Another kind of change is caused by rivers. When a river goes dowe a mountain,it cuts into the mountain. After a long time,the mountain us lower and the land is flatter.