Bulletin of the National Speleological Society - ISSN 0146-9517
Volume 28 Number 3: 127-132 - July 1966

A publication of the National Speleological Society

Electric-Analog Study of Cave Formation
M.S. Bedinger

Abstract

This study of limestone solution leading to cavern development is based on the following conditions: (1) the permeability of the limestone is low, but it contains and transmits water in joints, fractures, bedding-plane partings, and solution-channels; (2) at depth, the limestone aquifer is underlain by impermeable rock; (3) groundwater in the limestone is under water-table conditions; (4) recharge to the limestone is by infiltration of precipitation through the overlying rock to the zone of saturation; (5) discharge from the aquifer is by seeps and springs; (6) groundwater dissolved the limestone through which it flows, continuously modifying the flow pattern and the hydraulic properties of the medium. These conditions commonly are found in terrains of limestone of Paleozoic age in the eastern and central United States. An electrical analog conforming to these conditions has been constructed and used to define the pattern and density of groundwater flow and the relative length of time that water is in contact with the aquifer. Successive models are used to illustrate progressive limestone solution and changes in groundwater flow in the aquifer. The initial analog indicates a strongly convex water table with the greatest density of flow at shallow depth beneath the water table near the point of discharge. Successive models indicate greater concentration of flow near and on the level of groundwater discharge, an over-all lowering of the water table, and a pronounced flattening of the water table near the discharge point.

Results of the analog study support the following conclusions: (1) solution channels generally decrease in size with depth and with lateral distance from the pont of groundwater discharge; (2) the larger solution channels are above or near the elevation of the point of discharge and have greater lateral and vertical extent. This second observation supports the theory that the major zone of cave formation is at shallow depth beneath the water table.

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