Title: Natural arch - Wikipedia
Headings: Natural arch
Natural arch
Contents
Coastline
Weather-eroded arches
Water-eroded arches
Cave erosion
Arches as highway or railway bridges
Notable natural arches
Africa
Antarctica
Asia
Europe
North America
Canada
Caribbean
Mexico
United States
Oceania
Australia
New Zealand
South America
See also
References
External links

Content: By contrast, the Dictionary of Geological Terms defines a natural bridge as a "natural arch that spans a valley of erosion." The largest natural arch, by a significant margin, is the Xianren Bridge in China, with a span of 122 ± 5 meters (400 ± 15 ft). Contents
1 Coastline
2 Weather-eroded arches
3 Water-eroded arches
4 Cave erosion
5 Arches as highway or railway bridges
6 Notable natural arches
6.1 Africa
6.2 Antarctica
6.3 Asia
6.4 Europe
6.5 North America
6.5.1 Canada
6.5.2 Caribbean
6.5.3 Mexico
6.5.4 United States
6.6 Oceania
6.6.1 Australia
6.6.2 New Zealand
6.7 South America
7 See also
8 References
9 External links
Coastline
The Azure Window, Malta, which collapsed in 2017
On coasts two different types of arches can form depending on the geology. On discordant coastlines rock types run at 90° to the coast. Wave refraction concentrates the wave energy on the headland, and an arch forms when caves break through the headland. Two examples of this type of arch are London Arch —previously known as London Bridge—in Victoria, Australia, and Neill Island in the Andaman Islands, India. When these arches eventually collapse, they form stacks and stumps. On concordant coastlines rock types run parallel to the coastline, with weak rock such as shale protected by stronger rock such as limestone. The wave action along concordant coastlines breaks through the strong rock and then erodes the weak rock very quickly. Good examples of this type of arch are the Durdle Door and Stair Hole near Lulworth Cove on Dorset 's Jurassic Coast in south England.