Fact 1: Most canyons are formed by flowing rivers through erosion over long periods of time.

Fact 2: Deep gorges and canyons formed by the river are tourist attractions.

Given the two facts above, answer the question "What are formed by flowing rivers through erosion over long periods of time?" with the following options: 
- Sediment
 - soft soil
 - forests
 - deep gorges
 - cloud cover
 - patch reefs
 - big oceans
 - kalenchoes


 

    deep gorges     