The influence of urbanization of sinkhole development in central Pennsylvania |
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Authors: | Elizabeth L White Gert Aron William B White |
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Institution: | (1) Department of Civil Engineering and Institute for Research on Land and Water Resources, The Pennsylvania State University, 16802 University Park, Pennsylvania;(2) Department of Geosciences Materials Research Laboratory, The Pennsylvania State University, 16802 University Park, Pennsylvania |
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Abstract: | The karsted limestone valleys of central Pennsylvania contain two populations of sinkholes. Solution sinkholes occur in the
Champlainian limestone units along the margins of the valleys. Solution sinkholes are permanent parts of the landscape and,
although a nuisance to construction, do not present other problems. The second population is the suffosional or soil-piping
sinkholes These occur on all carbonate rock units including the Beekmantown and Gatesburg dolomites that comprise the two
principal carbonate aquifers in the valley. Suffosional sinkholes are the principal land-use hazard.
Suffosional sinkholes are transient phonomena. They occur naturally but are exacerbated by runoff modifications that accompany
urbanization Suffosional sinkholes are typically 1.5–2.5 m in diameter depending on soil thickness and soil type. The vertical
transport of soil to form the void space and soil arch that are the precursors to sinkhole collapse is through solutionally
widened fractures and cross-joints and less often through large vertical openings in the bedrock. The limited solution development
on the dolomite bedrock combined with soil thickness, seldom greater than 2 m, limits the size of the sinkholes. All aspects
of suffosional sinkhole development are shallow processes: transport, piping, void and arch formation, and subsequent collapse
take place usually less than 10 m below the land surface
Factors exacerbating sinkhole development include pavement, street, and roof runoff which accelerates soil transport Such
seemingly minor activities as replacing high grass and brush with mowed grass is observed to accelerate sinkhole development.
Dewatering of the aquifer is not a major factor in this region |
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