Most canyons are formed by flowing rivers through erosion over long periods of time, and rivers and glaciers are made of water. Given these facts, flowing water forms most canyons through erosion over what among the following options:
- movement of tectonic plates
 - dry streambeds
 - long periods of time
 - Physical weathering
 - Time and energy
 - short periods of time
 - massive damage
 - calving glaciers


 

   long periods of time      