Editing Natural arch (section)

==Cave erosion==
[[File:London Bridge before collapse.jpg |thumb| [[London Bridge (Victoria)|London Bridge]], [[Victoria (Australia)|Victoria]], Australia, before its partial collapse in 1990]]
Natural bridges can form from natural [[limestone]] [[cave]]s, where paired [[sinkhole]]s collapse and a ridge of stone is left standing in between, with the cave passageway connecting from sinkhole to sinkhole.

Like all rock formations, natural bridges are subject to continued erosion, and will eventually collapse and disappear.  One example of this was the double-arched [[Victoria (Australia)|Victoria]]n coastal rock formation, [[London Bridge (Victoria)|London Bridge]], which lost an arch after storms increased erosion.<ref>{{cite web|url=http://www.trekearth.com/gallery/Oceania/Australia/photo206866.htm|title=Port Campbell|website=www.trekearth.com|url-status=live|archive-url=https://web.archive.org/web/20080908102543/http://www.trekearth.com/gallery/Oceania/Australia/photo206866.htm|archive-date=September 8, 2008}}</ref>

[[Moon Hill]] in [[Yangshuo]], [[Guizhou Province]], China, is an example of an arch formed by the remnant of a [[karst]] limestone cave.