Atlantic Seaboard Fall Line
Atlantic Seaboard fall line | |
|---|---|
 Map showing part of the Eastern Seaboard Fall Line where the pale-colored coastal plain meets the brightly colored Piedmont. | |
| Location | United States |
| Formed by | New Jersey, Virginia, the Carolinas, Georgia, Alabama, U.S.[1][2][3] |
| Dimensions | |
| • Length | 900 mi (1,400 km)[3] |
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.[3] 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.
Before navigation improvements, such as locks, the fall line was generally the 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 as 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 link many of the fall-line cities.
In 1808, Treasury Secretary Albert Gallatin noted the significance of the fall line as an obstacle to improved national communication and commerce between the Atlantic seaboard and the western river systems:[4]
The most prominent, though not perhaps the most insuperable obstacle in the navigation of the Atlantic rivers, consists in their lower falls, which are ascribed to a presumed continuous granite ridge, rising about one hundred and thirty feet above tide water. That ridge from New York to James River inclusively arrests the ascent of the tide; the falls of every river within that space being precisely at the head of the tide; pursuing thence southwardly a direction nearly parallel to the mountains, it recedes from the sea, leaving in each southern river an extent of good navigation between the tide and the falls. Other falls of less magnitude are found at the gaps of the Blue Ridge, through which the rivers have forced their passage...
Gallatin's observation was sound, though simplified and limited by the knowledge of his time. The limits of the Fall Line are subject to some dispute. In the north, the fall line is usually understood to have its northern limit at New Brunswick, New Jersey, a geologic continuation in fact crosses the Hackensack and Passaic rivers at the cities of those names, to which navigation was possible. In the south, some such as Gallatin above, and the USGS source in the infobox, imply its end to be in the Carolinas or Georgia, and to include only rivers running to the Atlantic; but it is more accurate, as the Georgia source in the infobox does, to trace it farther west through Georgia and Alabama, as that is the geologic continuation.[5]
Cities and towns
[edit]Only the principal city of an area is listed below. However, two cities may belong on one river, if the one downstream is at the effective head of navigation and the one upstream at the site of useful water power.
Cities that lie along the Piedmont–Coastal Plain fall line include the following (from north to south):
- New Brunswick, New Jersey on the Raritan River.
- Trenton, New Jersey, on the Delaware River.[3]
- Philadelphia, Pennsylvania, on the Schuylkill River.[6]
- Wilmington, Delaware, on the Brandywine River.
- Havre de Grace, Maryland, on the Susquehanna River/head of Chesapeake Bay.
- Baltimore, Maryland, on Herring Run, Jones Falls, and Gwynns Falls.[7]
- Washington, D.C., on the Potomac River.[8]
- Fredericksburg, Virginia on the Rappahannock River.[8]
- Richmond, Virginia, on the James River.[9]
- Goldsboro, North Carolina and Smithfield, North Carolina, on the Neuse River.[10]
- Fayetteville, North Carolina, on the Cape Fear River.[citation needed]
- Columbia, South Carolina, on the Congaree River.[2][9]
- Augusta, Georgia, on the Savannah River.[2]
- Macon, Georgia, on the Ocmulgee River.[2]
- Columbus, Georgia, on the Chattahoochee River.[2]
- Tuscaloosa, Alabama, on the Black Warrior River.[2]
- Wetumpka, Alabama, on the Coosa River. The river and fall line run along the outside slope of the Wetumpka meteor impact crater, through an uplifted area. The crater is 82 MYA and the fall line is over 200 MYA.[11][12]
Geographic coordinates
[edit] |
References
[edit]- ^ "The Fall Line". A Tapestry of Time and Terrain: The Union of Two Maps - Geology and Topography. USGS.gov. Retrieved August 12, 2010.
{{cite web}}: CS1 maint: url-status (link)[dead link] - ^ a b c d e f "Georgia Geology". Archived from the original on September 4, 2010. Retrieved August 13, 2010.
- ^ a b c d Freitag, Bob; Susan Bolton; Frank Westerlund; Julie Clark (2009). Floodplain Management: A New Approach for a New Era. Island Press. p. 77. ISBN 978-1-59726-635-2. Retrieved November 17, 2010.
- ^ [Report on] Roads and Canals, Communicated to the Senate April 4, 1808, p.729
- ^ [1], especially the first section and maps.
- ^ Shamsi, Nayyar (2006). Encyclopaedia of Political Geography. Anmol Publications. pp. 92–93. ISBN 978-81-261-2406-0. Retrieved November 17, 2010.
- ^ "Maryland Geology". Maryland Geological Society. Retrieved January 25, 2017.
- ^ a b Deane, Winegar (2002). Highroad Guide to Chesapeake Bay. John F. Blair. p. 5. ISBN 978-0-89587-279-1. Retrieved November 17, 2010.
- ^ a b Roberts, David C.; W. Grant Hodsdon (2001). Roger Tory Peterson (ed.). A Field Guide to Geology: Eastern North America. Houghton Mifflin Harcourt. p. 242. ISBN 978-0-618-16438-7. Retrieved November 17, 2010.
- ^ "Fall Line". NCpedia. Retrieved January 25, 2017.
- ^ "Expert gives story on fall line through city". The Wetumpka Herald. June 3, 2020. Retrieved September 21, 2025.
Lock 31 is there because of the fall line. That's where everything changes right there. That one spot right there is a paradigm shift.
- ^ "Impact Crater". Wetumpka Area Chamber of Commerce. Archived from the original on January 10, 2018. Retrieved March 4, 2017.
The location of the Wetumpka Astrobleme —"star-wound"— originated from a cosmic event that occurred some 80 to 83 million years ago. It was confirmed only recently, after more than two years of extensive investigation and deep earth core drilling conducted on site. It is one of the few above-ground impact crater locations in the United States and one of only about six in the entire World. Even more unusual is the fact that the structure is actually exposed (as you can see from the rim evidence in these photographs). Despite the weathering that has occurred through millions of years, the crater walls are still prominent, so the rim was obviously much higher at one time. The projectile of the meteor impact was probably travelling between 10 and 20 miles per second. So this means the impact would have produced winds in excess of 500 miles per hour, and the meteor most likely struck at a 30-45 degree angle as it came from the northeast. They determined that it came from the northeast by the angle at which the rocks are slanted within the impact area which includes the current flow path of the Coosa River. This can be seen looking from both directions on the Bibb Graves Bridge. Geologists speculate that the shock waves, the damage, and other effects of the impact explosion radiated out from the strike several hundred miles. Debris may have been thrown as far away as the present Gulf of Mexico. Geologists also theorize that the strike area would have been under a shallow sea, perhaps 300 to 400 feet of water, that covered most of southern Alabama at the time of the impact. It is estimated that the diameter of the meteorite to be 1,100 feet and could have been as much as three to four times larger.
- ^ "History/Culture". PatapscoHeritageGreenway.org. Archived from the original on March 10, 2010. Retrieved September 7, 2010.
George Ellicott House: A block away is the 1789 George Ellicott House at 24 Frederick Road., which has been saved, moved out of the flood plain, and restored. The Ellicott family settled here along the fall line of the Patapsco River in 1772 and built an innovative, water-powered flour mill
- ^ "Watershed Report for Biological Impairment of the Patapsco Lower North Branch Watershed in Anne Arundel, Baltimore, Carroll, and Howard Counties and Baltimore City, Maryland. Biological Stressor Identification Analysis. Results and Interpretation" (PDF). Maryland Department of the Environment. April 2009. Archived from the original (PDF) on June 21, 2009.
- ^ "Fall Line". VirginiaPlaces.org. Retrieved August 13, 2010.
- ^ "River and "Fall Line" Cities". VirginiaPlaces.org. Retrieved August 13, 2010.