A fall line (or fall zone) is the area where an upland region and a coastal plain meet and is especially noticeable at the place rivers cross it, with resulting rapids or waterfalls. The uplands are relatively hard crystalline basement rock, and the coastal plain is softer sedimentary rock. A fall line often will recede upstream as a river cuts out the uphill dense material, forming "c"-shaped waterfalls and exposing bedrock shoals. Due to these features, riverboats typically cannot travel any further inland without portaging, unless locks are built. The rapid change of elevation of the water and resulting energy release make the fall line a good location for water mills, grist mills, and sawmills. Seeking a head of navigation with a ready supply of water power, people have long made settlements where rivers cross a fall line.
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👉 Fall line in the context of Three Notch'd Road
Three Notch'd Road (also called Three Chopt Road) was a colonial-era major east-west route across central Virginia. It is believed to have taken its name from a distinctive marking of three notches cut into trees to blaze the trail. By the 1730s, the trail extended from the vicinity of the fall line of the James River at the future site of Richmond westerly to the Shenandoah Valley, crossing the Blue Ridge Mountains at Jarmans Gap. In modern times, a large portion of U.S. Route 250 in Virginia follows the historic path of the Three Notch'd Road, as does nearby Interstate 64.
Fall line in the context of Coastal plain
A coastal plain (also coastal plains, coastal lowland, coastal lowlands) is an area of flat, low-lying land adjacent to a sea coast. A fall line commonly marks the border between a coastal plain and an upland area.
Fall line in the context of Head of navigation
The head of navigation is the farthest point above the mouth of a river that can be navigated by ships. Determining the head of navigation can be subjective on many streams, as the point may vary greatly with the size or the draft of the ship being contemplated for navigation and the seasonal water level. On others, it is quite objective, being caused by a waterfall, a low bridge that is not a drawbridge, or a dam without navigation locks. Several rivers in a region may have their heads of navigation along a line called the fall line.
Longer rivers such as the River Thames may have several heads of navigation depending on the size of the vessel. In the case of the Thames, that includes London Bridge, which historically served as the head of navigation for tall ships; Osney Bridge in Oxford, which has the lowest headroom of any bridge on the Thames that generally restricts navigation to smaller vessels such as narrowboats and cabin cruisers, and the long reach above St John's Lock, the first lock downstream of the river’s source, on the outskirts of Lechlade, where the river can become treacherously narrow and shallow for anything but small motorboats and human-powered vessels.
Fall line in the context of Atlantic Seaboard fall line
The Atlantic Seaboard Fall Line, or Fall Zone, is a 900-mile (1,400 km) escarpment where the Piedmont and Atlantic coastal plain meet in the eastern United States. Much of the Atlantic Seaboard fall line passes through areas where no evidence of faulting is present.
The fall line marks the geologic boundary of hard metamorphosed terrain—the product of the Taconic orogeny—and the sandy, relatively flat alluvial plain of the upper continental shelf, formed of unconsolidated Cretaceous and Cenozoic sediments. Examples of Fall Zone features include the Potomac River's Little Falls and the rapids in Richmond, Virginia, where the James River falls across a series of rapids down to its own tidal estuary.
Fall line in the context of Danville, Virginia
Danville is an independent city in the Commonwealth of Virginia in the United States. The city is located in the Southside Virginia region and on the fall line of the Dan River.
The city was a center of tobacco production and was an area of Confederate activity during the American Civil War, due to its strategic location on the Richmond and Danville Railroad. In April 1865, Danville briefly served as the third and final capital of the Confederacy before its surrender later that year.