AQUIFER-RELATED TERMS -- A GLOSSARY OF KARST TERMINOLOGY

aquifer
A formation, a group of formations, or part of a formation that contains sufficient saturated permeable material to yield significant quantities of water to wells and springs.
bedrock-collapse sinkhole
Formed by the collapse of a bedrock roof into an underlying cave. Bedrock collapse in karst is rare, but is the principal origin of karst window.
cave
Any natural opening in bedrock large enough for an adult to enter. A diameter of 50 centimeters (20 inches) and a length or depth of 2 meters (6.5 feet) are approximate minimal dimensions. Most cavers, however, would not count anything less than 10 meters (30 feet) long or deep. Orientation of the cave in space is not definitive, and an open-air pit with no overhanging ledges is a cave if it meets the minimum dimensions. The orientation relevant to the outcrop can be significant: an opening 6 feet wide and 2 feet deep in a cliff is an overhang or rock shelter, and not accepted as a cave.
cover collapse
The collapse of unconsolidated cover (soil, regolith, residium, or outwash) into the underlying cavernous bedrock.
cover-collapse sinkhole
Formed by the collapse of the unconsolidated cover (soil, residuum, loess, or till) that formed the roof of a soil void or conduit at the soil-bedrock interface, spanned a grike (cutter), or other karst void in the bedrock.
dissolution sinkhole (synonym: doline)
Sinkhole resulting exclusively from gradual dissolution of the bedrock and removal of the dissolved rock and insoluble residuum via the sinkhole throat and karst aquifer conduits. Variants of dissolution sinkholes may be totally buried and filled, or the bedrock may be totally exposed, but most have the classic bowl-shaped contour, with a variable thickness of soil or other unconsolidated residuum covering the bedrock.
epikarst (synonym: subcutaneous zone)
The interval below the organic soil and above the main mass of largely unweathered soluble bedrock, consisting of highly corroded bedrock, residuum, and float. Thickness varies from absent to a maximum of 30 meters (100 feet). The epikarst is relevant to the storage and transport of water in the karst system, and to foundation stability.
graded-filter technique
A method of filling sinkholes that allows the infiltration of water while preventing erosion of the soil cover into the karst conducts. The sinkhole throat openning in the rock bed is bridged with boulder-size pieces of stone. The large stones are covered with a second layer of stone large enough to bridge the openings in the first layer. The hole is finally filled to the ground level with coarse sand and top soil.
grike
A vertical or subvertical fissure in a limestone pavement developed by solution along a joint.
joint
A break of geological origin in the continuity of a body of rock occurring either singly, or more frequently in a set or system, but not attended by a visible movement parallel to the surface of the discontinuity.
karst
A terrain, generally underlain by limestone or dolomite, in which the topography is formed chiefly by the dissolving of rock, and which may be characterized by sinkholes, sinking streams, closed depressions, subterranean drainage, and caves (Monroe, W.H., 1970, A glossary of karst terminology: U.S. Geological Survey, Water-Supply Paper 1899, 26 p). The term "terrain" implies that only the surface is considered, whereas "terrane" includes the subsurface (caves or aquifer) as a single system. Karst also forms on gypsum and salt bedrock, although not in Kentucky.
karst aquifer
A body of soluble rock that conducts water principally via a connected network of tributary conduits, formed by the dissolution of the rock, which drain a groundwater basin and discharge to at least one perennial spring. The conduits may be partly or completely water filled. The karst aquifer may also have primary (intergranular) and secondary (fracture) porosity openings, which are saturated with water when below the potentiometric surface (water table).
karst cave -- see cave
karst conduit
A tubular opening created by dissolution of the bedrock, which carries, can carry, or has carried water flow. Conduits are defined as having a minimum diameter of 1 centimeter (1/2 inch) up to a maximum diameter of 0.5 meter (20 inches). Flow in a conduit may be year round, seasonal, high-flow only, or the conduit may be permanently dry.
karst valley
A valley-scale, mid-size, closed depression otherwise meeting the definition of a sinkhole but also enclosing more than one smaller sinkhole and sinking stream.
sinkhole
Any closed depression in soil or bedrock formed by the erosion and transport of earth material from below the land surface, which is circumscribed by a closed topographic contour and drains to the subsurface. Morphologies of sinkholes formed in soluble rock include dissolution sinkhole or doline (gently sloping depression that is wider than it is deep), karst window (sinkhole exposing an underground stream), vertical shaft (depressions in bedrock much deeper than it is wide and roughly circular in plan), grike (depression in bedrock much deeper than wide and cruely shaped like a lense (lenticular in plan).
sinking stream
Any stream that disappears underground, typically into a swallow hole.
spring
Any natural discharge of water from rock or soil onto the surface of the land of into a body or surface water.
swallow hole
A place where water disappears or sinks underground. A swallow hole generally imples nearly instantaneous water loss into an opening at the bottom of a sinkhole or karst valley, whereas a swallet may refer to gradual water loss into the gravel along a streambed, with no depression apparent.
topography
The general configuration of the land surface or any part of the earth's surface, including its relief and the position of its natural and man-made features. Maps of the topography commonly represent the shape of the surface with contour lines of constant elevation. Sinkholes are represented by contours that form a closed loop, and are marked with a series of tick marks on the interior or downslope side.

Reference for Glossary
Field, M.S., 1999, A lexicon of cave and karst terminology with special reference to environmental karst hydrology: U.S. Environmental Protection Agency, National Center for Environmental Assessment, EPA/600/R-99/006, 201 p. Digital version by Karst Waters Institute.