Karst Natural Bridge Landscape

When the roof of a subterranean river collapses, the ends remain connected and touch the ground, forming a suspended bridge-like feature called a karst natural bridge. Although the term karst natural bridge has been commonly used, its definition is not completely consistent. Practically, it is difficult to make a strict distinction between a karst natural bridge and a light-through cavity (subsurface flow). Therefore, some academics suggest that a karst natural bridge should be defined based on the condition that sunlight can reach the entire channel. Based on this standard, the channel length of the cave beneath a karst natural bridge (which equals the width of the bridge surface) should be limited to a maximum of 180 m. Karst natural bridges are common in southwestern China. The bridge across the Buliu River in Leye County, Guangxi Province, has a thickness of 78 m, an arch height of 67 m, an arch span of 177.14 m and a bridge width of 19.3 m, and the ridge height is 145 m. Along...