pick from the following.
* forces
* mechanical
* uncontrolled
* geological
* Water expanding
* flooding
* thrust
* barrel-shaped
Q: Fact 1: Most canyons are formed by flowing rivers through erosion over long periods of time. Fact 2: Geological erosion is natural occurring erosion over long periods of time. Given the two facts above, most canyons are formed by rivers flowing and what type of erosion?
A:
geological