| DARK ADAPTATION | Of eyes, a change in the retina sensitising it to dim light. (becoming accustomed to the dark). The reverse is 'Light adaption'. Cave - Biota. Ref JJ |
| DARK ZONE | The part of a cave in perpetual darkness, that lies beyond the Twilight zone. see Transition zone. Cave - Parts of. Ref JJ |
| DAYLIGHT HOLE | An opening to the surface in the roof of a cave. Cave - Parts of. Ref JJ |
| DEAD CAVE | A cave without streams or drips of water. Cave - Kinds of. Ref JJ |
| DECLINATION | The angle from true (or grid) north to magnetic north, at a given time and place. Survey & Mapping term. Ref JJ |
| DECOMPOSERS | Living things, chiefly bacteria and fungi, that live by extracting energy from tissues of dead animals and plants. Miscellaneous terms. Ref JJ |
| DECORATION | Cave features due to secondary mineral precipitation, usually of calcite, but also Aragonite, Gypsum, Salt, Ice, Lava and other rarer minerals. Also called Speleothem. Cave - Depositional Features. Ref JJ |
| DECORATION TYPES | Pendulite, Rimstone, R dam, R pool, Roof crust, Shawl, Speleogen, Stalagmite, Stalactite, Stegamite, Straw, Travertine. Cave - Depositional Features. Ref MM |
| DECORATION TYPES | Column, Curtain, Dog tooth spar, Drape, Driphole, Dripstone, Eccentric, Floe calcite, Flowstone, Gour, Helictite, Heligmite, Karren, Moonmilk, Cave - Depositional Features. Ref MM |
| DEFLATION | The removal of loose fine grained material from a surface by wind action. One way of forming hollows that are not karst. Geology. Ref KG |
| DENDRITIC | In caves, a network formed by the merging of small channels which in turn merge to form larger ones. cf Branchwork. Fauna. Ref MM |
| DESCENDER | A mechanical device for descending ropes. Climbing and SRT. Ref JJ |
| DETRITIVORES | Pertaining to detritus-feeding invertebrates. Fauna. Ref MM |
| DETRITUS | 1. Aggregate of fragments from organic structures as detached or broken down tissues. Small pieces of dead and decomposing plants and animals. 2. Material formed by mechanical breakage or abrasion of parent rocks. Fauna. Ref KG |
| DEVELOPED SECTION | A long section through a cave, usually from the entrance to the end of the cave, with the centreline being along the usual path. Survey & Mapping term. Ref JJ |
| DIAGENESIS | Post-depositional modification to a sediment that converts it into rock. Typically involves compaction, cementation and induration. Geology. Ref KG |
| DIG | An excavation made (1) to discover a new cave (2) to extend an existing cave (3) to uncover artifacts or animal bones. Speleology term. Ref JJ |
| DIKE | A body of igneous rock that cuts across the structure of adjacent rocks. Sometimes intruding into or exposed in cave fissures and passages. Geology. Ref MM |
| DIP | In surveying, the angle above or below horizontal of the current survey leg. Speleology term. Ref JJ |
| DIP | The angle at which beds are inclined from the horizontal, being the maximum angle of the bedding planes at right angles to the strike. Geology. Ref JJ |
| DISCHARGE | The outflow drainage of Aquifer waters. Hydrology terms. Ref AC |
| DISJUNCT DISTRIBUTION | The separate occurrences of similar species in separate karst areas. These species are related to a (now extinct) common ancestor that was widespread, & a surface dweller. cf: Distributional relict, Phylogenetic Cave - Biota. Ref AC |
| DISTRIBUTIONAL RELICT | Relates to a species surviving in an area isolated from the main or original distribution area. Usually a result of broad scale environmental events such as glaciation, continental drift. eg Gondwanan or Pangean relict species. Cave - Biota. Ref AC |
| DOG TOOTH SPAR | A speleothem, being calcite with acute pointed crystals. Cave - Depositional Features. Ref JJ |
| DOLINE | Sides may be gently sloping to vertical or overhanging. Size: a few metres to many hundreds of metres across, . See also Cenote, Sinkhole, Polje, Uvala, Solution doline, Subsidence doline & Collapse doline. Karst - Depression Features of. Ref JJ |
| DOLINE | A closed depression draining underground in karst, formed by Solution and or Collapse of underlying rock strata. Shape is variable, but often conical or bowl shaped. Karst - Depression Features of. Ref JJ |
| DOLINE KARST | Karst dominated by closed depressions, chiefly dolines, perforating a simple surface. Karst - Kinds of. Ref JJ |
| DOLOMITE | A mineral, or a carbonate rock consisting of calcium magnesium carbonate CaMg(CO3)2. Karst - Kinds of. Ref JJ |
| DOLOMITE CAVE | A cave in dolomite rock. Cave - Kinds of. Ref MM |
| DOMAIN | A biological region of the earths crust. Cave - Biota. Ref JJ |
| DOME | A hemispheroidal hollow in the roof of a cave, formed by breakdown or salt weathering. Some caves end at a dome. Cave - Parts of. Ref JJ |
| DOME SYNDROME | The tendency for cavers to go to the known end of a cave, especially when without due regard for the cave itself nor for its contents. Term coined from a cave where the final chamber is a dome and in which the practice was common. Miscellaneous terms. Ref MM |
| DONGA | In the Nullarbor plain, a closed depression generally hundreds of metres across and often from 2 to 5 metres deep. Dongas have very gentle slopes and flat clay-loam floors. Often contain trees when the surrounding country is treeless. Karst - Depression Features of. Ref JJ |
| DRIPHOLE | A hole formed by water dripping onto a cave floor. May be a metre deep or even deeper. May form in sediments or rock. Cave - Erosional & Solutional Features. Ref JJ |
| DRIPLINE | A line on the ground at a cave entrance formed by drips from the rock above. A dripline defines the beginning of a cave. Important to archaeologists in both Rock Shelters and Caves. Speleology term. Ref JJ |
| DRIPSTONE | A speleothem formed where water drips fall from cave roofs and walls, usually of calcite. Cave - Depositional Features. Ref JJ |
| DRY CAVE | A cave without a running stream or a lake. cf Dead cave, Wet cave. Cave - Kinds of. Ref JJ |
| DRY VALLEY | A valley in karst terrain without a surface flow of water. The talweg of such a valley may undulate with many closed depressions, and there may no longer be a distinct channel. Karst - Depression Features of. Ref JJ |
| DUCK(UNDER) | A place where water is at or close to the cave roof for a short distance so that it can be passed only by submersion. Cave - Parts of. Ref JJ |
| DUNE LIMESTONE | Syn. Aeolian calcarenite. Karst - Kinds of. Ref JJ |
| DURICRUST | An indurated surface formed by weathering processes involving cementation of the surface soils and weathered rock by calcite (calcrete), iron oxides (ferricrete, or laterite), silica (silcrete) or other cements. Karst - Kinds of. Ref KG |
| DYE GAUGING | Determining stream discharge by inserting a known quantity of dye and measuring its concentration after mixing. Survey & Mapping term. Ref JJ |
| DYNAMIC PHREAS | A phreatic zone where water moves fast with turbulent flow under hydrostatic pressure. Speleology term. Ref JJ |