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Subclass GB
| GB3-5030 | Physical geography | |||
| GB400-649 | Geomorphology. Landforms. Terrain | |||
| GB447 | Climatic geomorphology | |||
| GB448 | Slopes | |||
| GB450-460 | Coasts | |||
| GB461-468.995 | Reefs | |||
| GB471-478.995 | Islands | |||
| GB500-555 | Mountains. Orography | |||
| GB561-649 | Other natural landforms: Floodplains, caves, deserts, dunes, etc. | |||
| GB651-2998 | Hydrology. Water | |||
| GB980-2998 | Ground and surface waters | |||
| GB980-992 | Watersheds. Runoff. Drainage | |||
| GB1001-1199.8 | Groundwater. Hydrogeology | |||
| GB1201-1598 | Rivers. Stream measurements | |||
| GB1601-2398 | Lakes. Limnology. Ponds. Lagoons | |||
| GB2401-2598 | Ice. Glaciers. Ice sheets. Sea ice | |||
| GB2601-2798 | Snow. Snow surveys | |||
| GB2801-2998 | Hydrometeorology | |||
| GB5000-5030 | Natural disasters | |||
