Journal of Cave and Karst Studies - ISSN 1090-6924
Volume 65 Number 2: 126-129 - August 2003

A publication of the National Speleological Society

Detection of sinkholes developed on shaly Ordovician limestones, Hamilton County, Ohio, using digital topographic data: Dependence of topographic expression of sinkholes on scale, contour interval, and slope
Patrick Applegate


The Ohio Geological Survey has recently published a map showing the locations of known and probable karst in Ohio. The map shows some areas of karst developed on the extremely shaly Ordovician limestone of Hamilton County, in the southwestern corner of the state. Detailed mapping of these sinkholes in Mt. Airy Forest, a municipal park near Cincinnati, shows that they occur only where the lower 10 m of the Corryville Member of the Grant Lake Formation is the surface bedrock. Of the many sinkholes in the study area, only one is evident on the 1:24,000 USGS topographic map. The expression of sinkholes on contour maps is dependent on the size of the sinkhole, as well as the scale of the map, the contour interval at which the topography is sampled, and the slope of the ground surface around the sinkhole. It is possible to determine the minimum size of sinkhole which will consistently be expressed on a given part of a contour map. Conversely, it is also possible to determine the scale and contour interval which will be necessary to consistently indicate the presence of sinkholes of a given minimum size.

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