Fall line

2025-09-03T01:14:52Z

2600:1700:6230:8300:DE3:4364:F48B:F1D2: Reworded to improve readability

{{Short description|Meeting point of uplands and coastal plain}}
{{About|the concept in geomorphology|fall line as a gradient|Fall line (topography)|other uses|Fall line (disambiguation)}}
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 [[waterfall]]s. The uplands are relatively hard [[Basement (geology)|crystalline basement rock]], and the [[coastal plain]] is softer [[sedimentary rock]].<ref name=schneider>{{cite book |last= Schneider |first= Craig W. |author2=Richard B. Searles |title= Seaweeds of the southeastern United States: Cape Hatteras to Cape Canaveral |year= 1991 |publisher= Duke University Press |isbn= 978-0-8223-1101-0 |pages= 5–7 |url= https://books.google.com/books?id=gWA5kv_0g3cC&pg=PA5 |access-date= 17 November 2010}}</ref> 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 [[portage|portaging]], unless [[Lock (water navigation)|locks]] are built. The rapid change of elevation of the water and resulting energy release make the fall line a good location for [[water mill]]s, [[grist mill]]s, and [[sawmill]]s. Seeking a [[head of navigation]] with a ready supply of water power, people have long made settlements where rivers cross a fall line.

==Geography==
[[File:Bulletin 426 Fig 2 Fall Line.jpg|thumb|right|300px|Diagram showing the Fall Line. [[USGS]] figure.]]
The slope of rivers crossing fall zones affected settlement patterns. For example, the fall line represents the inland limit of navigation of many rivers. Numerous cities along a fall line grew as a result of demand for transferring people and goods between land-based and water-based transportation at that place.<ref name=UGA>{{cite web |url=http://www.gly.uga.edu/railsback/1122EUSMISR.html |title=The Fall Line and major cities of the Eastern U.S.}}</ref>

==Examples==

===Atlantic Seaboard Fall Line===
{{main|Atlantic Seaboard Fall Line}}

The Atlantic Seaboard Fall Line, is a {{convert|900|mi|km|adj=on|abbr=off|order=flip}} [[escarpment]] where the [[Piedmont (United States)|Piedmont]] and [[Atlantic Coastal Plain]] meet in the eastern [[United States]].<ref name=freitag>{{cite book |last= Freitag |first= Bob |author2=Susan Bolton|author3=Frank Westerlund|author4=Julie Clark |title= Floodplain Management: A New Approach for a New Era |year= 2009 |publisher= Island Press |isbn= 978-1-59726-635-2 |page= 77 |url= https://books.google.com/books?id=e1lr3gQiO8gC&pg=PA77 |access-date= 17 November 2010}}</ref> Much of the Atlantic Seaboard fall line passes through areas where no evidence of [[Fault (geology)|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 outwash plain of the upper continental shelf, formed of unconsolidated [[Cretaceous]] and [[Tertiary period|Tertiary]] [[sediment]]s. Examples of the Fall Zone include the Potomac River's [[Little Falls (Potomac River)|Little Falls]] and the rapids in [[Richmond, Virginia]], where the [[James River]] falls across a series of rapids down to the tidal estuary of the James River.


===Canada===
The [[Laurentian Upland]] forms a long scarp line where it meets the [[Great Lakes–St. Lawrence Lowlands]], just north of the [[Saint Lawrence River|St. Lawrence]] river and estuary. Along this line, numerous rivers have carved falls and canyons (listed east to west):
*[[Saint Anne Falls]] and [[Canyon Sainte-Anne]] ([[Sainte-Anne-du-Nord River|River Sainte-Anne-du-Nord]])
*Chaudron à Gaudreault ([[Rivière aux Chiens (Côte-de-Beaupré)|Rivière aux Chiens]])
*Unnamed falls ([[Rivière du Sault à la Puce]])
*Canyon of the [[Cazeau River|River Cazeau]]
*[[Montmorency Falls]] ([[Montmorency River|River Montmorency]])
*[[Parc of the Kabir Kouba Cliff and Waterfall|Kabir Kouba Fall]] ([[Saint-Charles River (Quebec City)|River Saint-Charles]])
*Chute Ford ([[Sainte-Anne River (Les Chenaux)|River Sainte-Anne]])
*Sainte-Ursule Falls ([[Maskinongé River|River Maskinongé]])
*Chute à Magnan ([[Rivière du Loup (Mauricie)|Rivière du Loup]])
*Chutes Émery and Chute du Moulin Coutu ([[Rivière Bayonne]])
*Les sept chutes ([[L'Assomption River|River de L'Assomption]])
*[[Park of Dorwin Falls|Dorwin Falls]] ([[Ouareau River|River Ouareau]])
*Wilson Falls ([[Rivière du Nord (Laurentides)|Rivière du Nord]])
*Long Sault, now flooded by the [[Carillon hydroelectric generating station]] ([[Ottawa River]])
**The [[Chaudière Falls]] run over the unrelated Eardley Escarpment of the [[Ottawa-Bonnechere Graben]].
The [[Jacques-Cartier River|River Jacques-Cartier]] and [[Saint-Maurice River|River Saint-Maurice]] lack such noticeable features because they cross the scarp through [[U-shaped valley]]s. The falls of the lower Saint-Maurice (as well as those of the River Beauport, in [[Quebec City]]) are due to the [[fluvial terrace]]s of the [[Saint Lawrence river]] rather than the Laurentian Scarp.

==See also==
*[[Geologic map of Georgia (U.S. state)]]
*[[Spring line settlement]] - the analogous concept where access to fresh water is more important than navigation or power

==References==
{{Reflist}}

==External links==
*{{Cite EB1911|wstitle=Fall-line |short=x}}

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Fall line