Cave Erosion
Natural bridges can form from natural limestone caves, where paired sinkholes 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 Victorian coastal rock formation, London Bridge, which lost an arch after storms increased erosion.
Read more about this topic: Natural Arch
Famous quotes containing the words cave and/or erosion:
“Under the one word “house” are included the schoolhouse, the almshouse, the jail, the tavern, the dwellinghouse; and the meanest shed or cave in which men live contains elements of all these. But nowhere on the earth stands the entire and perfect house.”
—Henry David Thoreau (1817–1862)
“What if we fail to stop the erosion of cities by automobiles?... In that case America will hardly need to ponder a mystery that has troubled men for millennia: What is the purpose of life? For us, the answer will be clear, established and for all practical purposes indisputable: The purpose of life is to produce and consume automobiles.”
—Jane Jacobs (b. 1916)