#valley__vale  a long depression in the surface of the land that usually contains a river
  supertype:  natural_depression__naturaldepression__depression  a sunken or depressed geological formation
  instance:  San_Joaquin_Valley  Shenandoah_Valley
  subtype:  dale  (British) an open river valley (in a hilly area)
  subtype:  glen  (Scottish) a narrow secluded valley (in the mountains)
  subtype:  gully  deep ditch cut by running water (especially after a prolonged downpour)
     subtype:  arroyo  (southwestern United States) a stream or brook
     subtype:  draw  a gully that is shallower than a ravine
     subtype:  wadi  gully or streambed in North Africa and the Middle East that remains dry except during rainy season
  subtype:  holler__hollow  a small valley between mountains; "he built himself a cabin in a hollow high up in the Appalachians"
     subtype:  dell__dingle  a small wooded hollow
  subtype:  nullah  a ravine or gully in southern Asia
  subtype:  ravine  a deep narrow steep-sided valley (especially one formed by running water)
     subtype:  canyon__canon  (North America) a ravine formed by a river in an area with little rainfall
     subtype:  gorge  a deep ravine (usually with a river running through it)
        subtype:  gulch__flume  a narrow gorge with a stream running through it
        instance:  Grand_Canyon  Olduvai_Gorge
  subtype:  rift_valley  a valley with steep sides; formed by a rift in the earth's crust

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