TERMINOLOGY 121 



Dell A smaU secluded valley or vale ; a dale ; a ravine. 



Delta The low alluvial land, deposited in a more or less triangular 



form at the mouth of a river, which is often cut by several 

 distributaries of the main stream. 



Depression A general term signifying any depressed or lower area in the 



ocean floor; a hollow completely surroimded by higher ground 

 and having no natural outlet for surface drainage. 



Dike {0-6a) A bank of earth or stone to form a barrier; a levee. 



Dismal A swamp bordering on, or near, the sea, often enclosing knobs 



or hummocks; a pocosin. Local in South Atlantic States. 



Divide The line of separation between drainage systems ; the summit 



of an interfluve. The highest summit of a pass or gap. 



Dock {0-S5) The slip or waterway between two piers, or cut into the land 



for the reception of ships. 



Dome A smoothly rounded, rock-capped mountain summit, roughly 



resembling the dome or cupola of a building. 



Drain A channel; a trench; a watercourse, especially a narrow one. 



Dry dock (G-36) An artificial basin fitted with gate or caisson into which a ves- 

 sel may be floated and from which the water may be piunped 

 out to expose the bottom of the vessel. (Sometimes re- 

 ferred to as a graving dock.) 



Dry wash A wash, arroyo, or coulee in the bed of which there is no water, 



except at infrequent intervals and for short periods. 



Dune (A-4) A hill or ridge formed by the wind from sand or oth er granular 



material. 



Eddy {0-19) A current of water rimnng contrary to the main current or 



moving circularly; a whirlpool. 



Escarpment An extended fine of cliffs or bluffs ; a high steep face of rock ; an 



elongated and comparatively steep slope of the sea floor, 

 separating flat or gently sloping areas. 



Estuary That portion of a stream influenced by th e tide of the body of 



water into which it flows: an arm of the sea at a river mouth. 



Everglade A tract of swampy land covered mostly with tall grass; a 



swamp or inundated tract of low land. Local in the South. 



Fall (Jails) {C-20) A cascade, waterfall, or cataract; the flow or descent of one 



body of water into another. (Usually pi.) 



Fan A gently sloping, cone-shaped accumulation of material nor- 



maUy located at the mouth of a canj^on. 



Flat A level tra ct lying at 8 smaU depth below the surface of water, 



or alternately covered and left bare by the tide ("tidal 



flat", "mud flat"). 



Floating dock (0-37) A floating structure which can be submerged to receive a ves- 

 sel, and then floated to expose the bottom of the vessel. 



Floodgate A gate for shutting out, admitting, or releasing a body of 



water; a sluice. 



Floor The bed or bottom of the ocean . A comparatively level valley 



bottom; any low-lying ground surface. 



Foot The bottom of a slope, grade or declivity. A term for the 



lower part of any elevated land form. 



