Most canyons are formed by flowing rivers through erosion over long periods of time, and the Columbia River Gorge is a spectacular river canyon cutting through the volcanic rock of the Cascade Mountain Range. Given these facts, what was formed through erosion over long periods of time among the following options:
- Columbia River Gorge
 - a hydraulic system
 - swamp vegetation
 - Mississippi River delta
 - the Moon
 - Calcium carbonate
 - the Himalayan mountains
 - permineralization


 

 Columbia River Gorge        