- Stevin, Simon (1548-1620)
- Strategic Petroleum Reserve (Geologic considerations)
- Stratigraphy
- Stratosphere and Stratopause
- Stream Capacity and Competence
- Stream Piracy
- Stream Valleys, Channels, and Floodplains
- Strike and Dip
- Subduction Zone
- Sun (Stellar Structure)
- Supercontinents
- Superposition
- Surf Zone
- Surveying Instruments
- Suspended Load
- Syncline and Anticline
