Natural arch

A natural arch, natural bridge or, less commonly, a rock arch is a natural rock formation where a rock arch forms, with an opening underneath. Most natural arches form as a narrow bridge, walled by cliffs, become narrower from erosion, with a softer rock stratum under the cliff-forming stratum gradually eroding out until the rock shelters thus formed meet underneath the ridge, thus forming the arch. Natural arches commonly form where cliffs are subject to erosion from the sea, rivers or weathering (subaerial processes); the processes "find" weaknesses in rocks and work on them, making them larger until they break through.

The choice between bridge and arch is somewhat arbitrary. The Natural Arch and Bridge Society identifies a bridge as a subtype of arch that is primarily water-formed. 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).

Daniel Boone

Daniel Boone (November 2, 1734 [O.S. October 22] – September 26, 1820) was an American pioneer, explorer, woodsman, and frontiersman, whose frontier exploits made him one of the first folk heroes of the United States. Boone is most famous for his exploration and settlement of what is now Kentucky, which was then part of Virginia, but on the other side of the mountains from the settled areas. As a young adult, Boone supplemented his farm income by hunting and trapping game, and selling their pelts in the fur market. Through this occupational interest, Boone first learned the easy routes to the area. Despite some resistance from American Indian tribes such as the Shawnee, in 1775, Boone blazed his Wilderness Road through the Cumberland Gap in the Appalachian Mountains from North Carolina and Tennessee into Kentucky. There, he founded the village of Boonesborough, Kentucky, one of the first American settlements west of the Appalachians. Before the end of the 18th century, more than 200,000 Americans migrated to Kentucky/Virginia by following the route marked by Boone.