- "Galaxies can be classified by shape " is not relevant

- The formation of something is a kind of process
- If a process follows another process, then the other process begins that process
- Therefore, if the formation of something follows another process, then the other process begins the formation of that something

- Weathering is a kind of geologic process
- Erosion is a kind of process
- Hence, weathering and erosion are kinds of processes

- If the formation of something follows another process, then the other process begins the formation of that something
- Weathering and erosion are kinds of processes
- Hence, if the formation of something follows weathering and erosion, then weathering and erosion begin the formation of that something

- If the formation of something follows weathering and erosion, then weathering and erosion begin the formation of that something
- In the rock cycle , formation of sediments follows weathering and erosion
- So, weathering and erosion begin the formation of sediments

Hence, weathering and erosion begin the formation of sediments
Question
In the rock cycle, weathering and erosion begin the process of the formation of

Context
- In the rock cycle , formation of sediments follows weathering and erosion 
- Galaxies can be classified by shape 
- The formation of something is a kind of process 
- If a process follows another process, then the other process begins that process 
- Weathering is a kind of geologic process 
- Erosion is a kind of process