Erosion

Erosion moves soil or rock from one place to another. Rain, streams or landslides can all move soil or rock.

A river channel erodes on its outside banks. Fast-flowing water carries the ouside soil and deposits it on the inside banks where the water flows slowly. Over time, river channels migrate across the valley floor in the direction of the erosion.

A good example of this process is formation of an Oxbow Lake.

The Mississippi is not straight; it twists and turns, or "meanders." Sometimes the river twists back on itself and makes a loop. This loop separates gradually from the main part of the river. Sediment slowly fills the channel connecting the loop to the main river. Before long, the loop is cut off from the main river.

Formation of an oxbow lake is an important natural force that straightens the river.