- Erosion usually occurs over a period of many years which is considered a long time
- Water causes soil and rock erosion
- So, water will cause erosion to the rock over a long period of time

So, water will cause erosion to the rock over a long period of time
[Question]What happens when water flows over a rock for a long period of time?
[Context]- Erosion usually occurs over a period of many years which is considered a long time 
- Water causes soil and rock erosion