Deltas form when sediments carried by rivers are deposited at the mouth of the river. This happens when fast-moving river water slows as it enters a lake or ocean, causing sediments to settle. 

Over time, layers of sediment build outward, creating fertile, triangular-shaped landforms.

Deltas are landforms formed by water being deposited at the mouth of a river. 

Canyons form when moving water erodes and cuts through the Earth’s surface over very long periods of time. Flowing rivers slowly wear away rock and soil, making deep valleys with steep sides.

Canyons are a deep, narrow valley with steep sides. This landform is caused by weathering and erosion from water.

Sand dunes form when wind erodes and transports sand, then deposits it in one place when the wind slows or hits an obstacle. Changes in wind direction can cause dunes to move and change shape over time.

U-shaped valleys form when glaciers slowly move across the land, eroding rock and soil as they go. The heavy ice scrapes the ground, creating wide valleys with steep sides and a flat bottom. When the glacier melts, the U-shaped valley is left behind.