 Gaping Gill contains a waterfall disappearing underground into the Carboniferous limestone.The formation of Carboniferous Limestone was followed by the deposition of dark marine shales, siltstones and coarse sandstones of the Millstone Grit, notably in the area later uplifted to form the Pennine anticline.This sequence can be seen in the Yorkshire Dales with Ingleborough protruding up above the Carboniferous Limestone landscape below.