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31-21 Myriad Mini-Sinkholes Years After Forest Clearing: Groundwater and Old Stumps
Session: Environmental Geochemistry and Health (Posters)
Poster Booth No.: 47
Presenting Author:
Gregg Davidson
Authors:
Davidson, Gregg R.1, Chiu, Yung-Yu2
(1) University of Mississippi, University, USA, (2) Taiwan,
Abstract:
More than 100 small sinkholes, 12 to 50 cm wide and 10 to 80 cm deep, developed rapidly in sandy-clay soils in two adjacent fields in south-central Mississippi, USA, following installation and operation of a nearby high-capacity water well. The local area is not known for karst features, evaporite dissolution cavities, underground mining, soil erosion around manmade structures, or desiccation fractures of shallow clays. When studied several years after first appearing, the sinkholes had nearly vertical walls, with some cavities widening with depth. Some had tree stumps visible in the center. Further investigation found remnants of stumps or roots in and radiating outward from most of the sinkholes. Installation of piezometers along a transect revealed a continuous hydraulic gradient under the effected property toward the production well and evidence of reduced overall water levels. The most plausible cause of rapid sinkhole formation is (1) initial partial preservation of tree stumps in saturated soils created by a high water-table and capillary action, (2) lowering of the water table and aeration of surface sediments, and (3) accelerated decomposition of stumps faster than soil could creep into the cavities.