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During the Silurian Period (420 to 405 MYA) a shallow sea spread across Indiana. This sea deposited limestones along the southwest slope of the arch. Over the arch, the depth of the deposits diminish, thus layers 100 feet (30 m) northeast of the arch become only 10 feet (3.0 m) across the top of the arch. [4]
A natural arch, natural bridge, or (less commonly) rock arch is a natural landform where an arch has formed with an opening underneath. Natural arches commonly form where inland cliffs , coastal cliffs , fins or stacks are subject to erosion from the sea, rivers or weathering ( subaerial processes).
Without the constant presence of water, stacks also form when a natural arch collapses under gravity, due to sub-aerial processes like wind erosion. Erosion causes the arch to collapse, leaving the pillar of hard rock standing away from the coast—the stack. Eventually, erosion will cause the stack to collapse, leaving a stump.
The Nashville Dome of Tennessee and the Jessamine Dome or Lexington Dome [1] of central Kentucky make up the central portion of the arch. In the northern part, north of Cincinnati, Ohio, the Cincinnati Arch branches to form the Findlay and Kankakee arches. The Findlay plunges under Ontario and reappears as the Algonquin Arch further north. [2]
Feb. 24—The Federal Emergency Management Agency has presented coastal erosion hazard projections for Essex County, including Cape Ann, for 2030, 2050 and 2100.
The highest point in Indiana is Hoosier Hill, at 1,257 feet (383 m) above sea level in northern Wayne County. Rural areas in the central portion of the state are typically composed of a patchwork of fields and forested areas. The geography of Central Indiana consists of gently rolling hills and sandstone ravines carved out by the retreating ...
Hanging Rock National Natural Landmark is a 4-acre (1.6 ha) site in Wabash County, Indiana, [1] that was designated a National Natural Landmark in May 1986. [2] The site, located on the southern bank of the Wabash River near the town of Lagro, contains an impressive natural exposure of fossilized coral reef dating from the Silurian Period some 400 million years ago.