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| This view shows detail of boxwork - an unusual dissolution pattern on the surface of the limestone roof created by flowing groundwater when the cavern was filled with water long ago. Before the cavern formed, calcite had precipitated in fractures in the limestone. Later, as the limestone dissolve, the calcite that had filled the fractures was more resistant to erosion by water that had filled the cavern space. As the regional groundwater table slowly migrated downward, the caverns (with boxwork preserved) were left high and dry (Feldmann, 1997; NPS, 2009). |
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