[bert]

Why is this Karst?

I thought a Karst area involved vast areas where extensive underground caverns broke down and the resultant sinkholes drain into the cavernous area. There are extensive karst areas in East Tennessee and also extensive caves.

The formations pictures resemble sandstone arches in Utah and also here in East Tennessee resulting from surface river action.

[cogitator]

I thought a Karst area involved vast areas where extensive underground caverns broke down and the resultant sinkholes drain into the cavernous area. There are extensive karst areas in East Tennessee and also extensive caves.

Note that Smokin' Joe properly called this "late stage" karst development. What you describe is earlier stage. In late stage, much of the limestone has eroded away, leaving only the remnants of the former topography. I.e., late stage karst is more sinkhole than stone.