The three main causes of landform changes are erosion, deposition and weathering. Some main types of landforms are mountains, plains, plateaus, valleys and deltas. A landform like a mountain experiences gradual change through weather conditions such as rain and wind.
For mountain landforms to change, weathering must first occur. Weathering is a chemical and a physical process in which rocks become smaller in size due to weather and other conditions like frost action. These smaller pieces of rocks can be categorized as sediment types that include silt and sand.
After the weathering process, erosion takes place when these smaller sediment types are moved from one place to another. For example, rocks tumbling down a mountain causes a shift of rock from one area to another. It also causes a mountain to change or become eroded over time.
The erosion process leads to deposition of sediment to other locations to form landforms like a delta or sandbar. A delta forms near a river's mouth.