When rock particles have been moved to other places by rivers, they are said to be transported. This process is called erosion, and it occurs in a few ways:

* Abrasion: As the river flows, the rock particles bump and grind against each other and the riverbed, wearing them down and creating smaller particles.

* Attrition: The constant collision of rock particles against each other causes them to break down into smaller and smaller pieces.

* Solution: Certain minerals in the rocks can dissolve in the river water and be carried away.

The transported rock particles are then deposited in different locations, often downstream, in a process called sedimentation. This is how rivers form deltas, floodplains, and other landforms.