Fall line: Difference between revisions
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#REDIRECT [[Fall zone]] |
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{{otheruses4|a geomorphology feature|the notion of fall line in Alpine skiing|Fall line (skiing)}} |
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In [[geomorphology]], a '''fall line''' marks the area where an upland region (continental [[bedrock]]) and a [[coastal plain]] (coastal [[alluvium|alluvia]]) meet. Technically, a fall line is an [[unconformity]]. A fall line is typically prominent when crossed by a river, for there will often be rapids or waterfalls. Many times a fall line will recede upstream as the river cuts out the uphill dense material, many times forming “c” shaped waterfalls. Because of these features river boats typically cannot travel any farther inland without [[portage|portaging]] unless locks are built. On the other hand, the rapid change in elevation of the water, and the resulting energy release, makes the fall line a good location for a water mill. Because of the need for a port and a ready supply of water power, settlements often develop where rivers cross a fall line. |
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===The fall line in the United States=== |
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Along the eastern coast of the [[United States]], the east-facing [[escarpment]] where the [[Piedmont (United States)|Piedmont]] of the [[Appalachian Mountains|Appalachians]] descends steeply to the [[Atlantic_Coastal_Plain|coastal plain]] forms a fall line over 1500 [[kilometers]] long. This long fall line (also referred to as the Fall Zone) played a major role in settlement patterns along rivers, back into prehistoric times. It is often referred to simply as "the fall line" or "the fall zone". In some places the fall line may be abrupt, while in others it is a zone that may be many miles wide. Geologically the fall line marks the 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]] [[sediment]]s. Examples of the Fall Zone include the rapids in [[Richmond, Virginia]], where the [[James River (Virginia)|James River]] falls across a series of rapids down to the tidal estuary of the James River. |
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There are a few different theories as to how a Fall Line is formed or why they exist, and one in particular, brought forward by American Physiographer W.J. McGee states that a Fall Line is created through [[monoclinal]] faulting/flexing experienced in the region. While this theory is accepted by many geomorphologists much of the fall line along the east coast of the United States passes through areas where no evidence of [[faulting]] is present. |
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In the 19th Century, the fall line often represented the head of navigation on rivers at points like Little Falls or the [[Great Falls of the Potomac River|Great Falls]], on the Potomac River. However, since the advent of flumes for water supply and canals for shipping in the early 20th Century, the most prominent feature of fall line settlement was the establishment of the cities along it. As the cities were linked by the early highways, [[U.S. Route 1]] and [[Interstate 95]] came to pass through many of these cities, roughly tracing the fall line. |
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Cities along the Piedmont – Coastal Plain fall line include, from north to south: |
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*[[New Brunswick, New Jersey]] on the [[Raritan River]] |
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*[[Trenton, New Jersey]] on the [[Delaware River]] |
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*[[Philadelphia, Pennsylvania]] on the [[Schuylkill River]] |
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*[[Wilmington, Delaware]] on the [[Brandywine Creek]] |
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*[[Conowingo, Maryland]] on the [[Susquehanna River]] |
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*[[Baltimore, Maryland]] on the [[Patapsco River]] |
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*[[Laurel, Maryland]] on the [[Patuxent River]] |
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*[[Washington, D.C.]]/[[Georgetown, Washington, D.C.|Georgetown]]/[[Alexandria, Virginia|Alexandria]] on the [[Potomac River]] ([[Great Falls National Park]]) |
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*[[Occoquan, Virginia]] on the [[Occoquan River]] |
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*[[Fredericksburg, Virginia]] on the [[Rappahannock River]] |
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*[[Richmond, Virginia]] on the [[James River (Virginia)|James River]] |
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*[[Petersburg, Virginia]] on the [[Appomattox River]] |
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*[[Roanoke Rapids, North Carolina]] on the [[Roanoke River]] |
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*[[Smithfield, North Carolina]] on the [[Neuse River]] |
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*[[Cheraw, South Carolina]] on the [[Pee Dee River]] |
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*[[Camden, South Carolina]] on the [[Wateree River]] |
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*[[Columbia, South Carolina]] on the [[Congaree River]] |
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*[[Augusta, Georgia]] on the [[Savannah River]] |
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*[[Milledgeville, Georgia]] on the [[Oconee River]] |
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*[[Macon, Georgia]] on the [[Ocmulgee River]] |
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*[[Columbus, Georgia]] on the [[Chattahoochee River]] |
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*[[Wetumpka, Alabama]] on the [[Coosa River]] |
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*[[Tuscaloosa, Alabama]] on the [[Black Warrior River]] |
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Cities along other fall lines include: |
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*[[Lowell, Massachusetts]] on the [[Merrimack River]] |
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*[[Hartford, Connecticut]] on the [[Connecticut River]] |
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*[[Albany, New York]] on the [[Hudson River]] |
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==See also== |
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*[[Escarpment]] |
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*[[Fall Line Freeway]] |
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==References== |
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*[http://tapestry.usgs.gov/features/14fallline.html USGS: The Fall Line: A Tapestry of Time and Terrain] |
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*[http://www.virginiaplaces.org/regions/fallshape.html Virginia Places website: The Fall Line] |
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*[http://www.virginiaplaces.org/vacities/24river.html Virginia Places website: Rivers and Fall Line Cities] provides a more detailed explanation of why some towns and cities along a Fall line grew and others did not. |
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*[http://www.gly.uga.edu/default.php?PK=0&iPage=5#FallLine The Geology of Georgia] |
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[[Category:Geomorphology]] |
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Revision as of 02:24, 17 April 2008
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