One of the most pathological fluvial transitions must be from above ground to underground. Here the Fell Beck in North Yorkshire, England descends into Gaping Gill. This 105m pothole in Carboniferous Limestone forms England's tallest unbroken waterfall. The ground to the south is pockmarked with sinkholes, several of which provide access into the Gaping Gill cave system. The water emerges from Ingleborough Cave a couple of kilometres to the south.
P. Kyle House, PhD., Surficial Geologic Mapping Specialist / Geomorphologist