To determine the rate of cover-collapse sinkhole formation in Christian County, Kentucky, we used large scale aerial photographs taken nearly twenty years apart. The negatives were enlarged and printed to 1:3,000 scale and examined for collapses. The photographs constrained the time period within which the collapse could have occurred, and the large scale of the prints provided a means to identify, locate, and field-verify the cover collapses. All features noted on the photographs were checked in the field. Sinkholes seen on the later photographs, but not the earlier ones, were recorded. The rate of formation calculated was 0.2 cover-collapse km 22 yr 21 .
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