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Subject
- Groundwater135
- Rivers103
- Sequence stratigraphy102
- Water quality102
- Geology36
- Geology, Structural21
- Joints (Geology)20
- Local transit15
- Water-supply11
- Gravel9
- Sand9
- Geology, Stratigraphic7
- Sediments (Geology)5
- Bituminous coal--Pennsylvania--Maps4
- Gas wells--Pennsylvania--Maps4
- Glacial landforms4
- Mineral industries4
- Oil wells--Pennsylvania--Maps4
- Roads4
- Bicycles3