Here's why:

* Deposition: This is the process where sediments, soil, and rocks are added to a landform. It builds up land, creating things like deltas, sand dunes, and alluvial fans.

* Erosion: This is the process of wearing away and transporting rock, soil, and other materials. It carves out land, forming canyons, valleys, and other landforms.

How Canyons Form:

Canyons are typically formed by the erosive power of rivers, glaciers, or wind.

* River Erosion: As a river flows, it carries sediment and erodes the bedrock below. Over time, the river cuts deeper and wider, creating a canyon.

* Glacial Erosion: Glaciers are massive sheets of ice that move slowly and carve out land as they travel. They can form U-shaped valleys, which are often found alongside canyons.

* Wind Erosion: In arid regions, wind can pick up and carry sediment, eroding rock and creating canyons, especially in soft rock formations.

In Summary:

Canyons are formed by the removal of material (erosion), not the addition of material (deposition).