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fall line
A fall line (or fall zone) is the geomorphologic break between an upland region of relatively hard crystalline basement rock and a coastal plain of softer sedimentary rock. 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, often forming “c”-shaped waterfalls. Because of these features riverboats typically cannot travel any farther inland without portaging, unless locks are built there. 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 water mills, grist mills, and sawmills. Because of the need for a river port leading to the ocean, and a ready supply of water power, settlements often develop where rivers cross a fall line.
==United States==
The slope of fall zones on rivers played a role in settlement patterns. For example, the fall line represents the inland limit of navigation on many rivers. As such, many fall line cities grew around transferring people and goods between land-based and water-based transportation at this point. Also, fall lines proved useful for hydroelectric dams such as those at Rochester, New York (on the Niagara Escarpment), at Columbia, South Carolina, and at Conowingo, Maryland, on the Susquehanna River (on the Atlantic Seaboard fall line). Cities established along fall lines in the United States include:
*New England:
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*Lowell, Massachusetts (Merrimack River)
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*Hartford, Connecticut (Connecticut River)
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*Fall River, Massachusetts (Quequechan River)
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*Bangor, Maine (Penobscot River)
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*Augusta, Maine (Kennebec River)
*Atlantic Seaboard fall line (Southern fall line):
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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 Brandywine Creek
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*Baltimore, Maryland, on the Jones Falls, Gunpowder Falls and Gwynns Falls
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*Great Falls, Virginia, on the Potomac River
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*Fredericksburg, Virginia, on the Rappahannock River
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*Hanover, Virginia, on the North Anna River
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*Richmond, Virginia, on the 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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*Raleigh, North Carolina, on the Neuse River
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*Fayetteville, North Carolina, on the Cape Fear River
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*Columbia, South Carolina, on the Congaree River
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*Augusta, Georgia, on the Savannah River〔(【引用サイトリンク】title= Fall Line )〕
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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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*Tallassee, Alabama, on the Tallapoosa River
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*Wetumpka, Alabama, on the Coosa River
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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