Fact 1: Rocks interacting with wind over long periods of time causes weathering.

Fact 2: Erosion happens when water or wind wears away bits of rock.

Given the two facts above, answer the question "what causes weathering over long periods of time?" with the following options: 
- rocks
 - coastlines
 - respiration
 - alluvial
 - erosion
 - loose soil
 - rainfall
 - perspiration


 

     erosion    