Atlantic Seaboard Fall Line: Difference between revisions

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The '''Atlantic Seaboard Fall Line''', or '''Fall Zone''', is a {{convert|900|mi|km|adj=on}} [[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 [[faulting]] is present.

The [[fall line]] marks the geologic boundary of hard metamorphosed terrain&mdash;the product of the [[Taconic orogeny]]&mdash;and the sandy, relatively flat [[outwashalluvial plain]] of the upper continental shelf, formed of unconsolidated [[Cretaceous]] and [[Cenozoic]] [[sediment]]s. Examples of Fall Zone features include the [[Little Falls (Potomac River)|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.

Before navigation improvements such as locks, the fall line was generally the [[wikt:head of navigation|head of navigation]] on rivers due to their rapids or waterfalls, and the necessary [[portage]] around them. Numerous cities initially formed along the fall line because of the easy river transportation to seaports, as well the availability of water power to operate mills and factories, thus bringing together river traffic and industrial labor. [[U.S. Route 1]] and [[Interstate 95|I-95]] link many of the fall-line cities.