Fall line

Categories: Geology

The fall line has meanings in both geographical features and the sport of alpine skiing.

Geographical fall line

As a geographical feature, the fall line marks the area where an upland region (continental bedrock) and a coastal plain (coastal alluvia) meet. The fall line is typically prominent where a river crosses it, for there will usually be rapids or waterfalls. Because of these features river boats typically can not travel any further inland. Because of the need of a port, and ready supply of water power, settlements often developed where the river crosses the fall line.

Along the eastern coast of the United States, the escarpment where the Piedmont of the Appalachian Rise descends to the coastal plain forms a fall line over 1500 kilometers long. The most prominent example of fall line settlement was the establishment of the cities along it, including, from north to south:

• Pawtucket, Rhode Island on the Blackstone River
• Troy, New York on the Hudson River
• Trenton, New Jersey on the Delaware River
• Washington, D.C. (originally Georgetown in Maryland) on the Potomac River
• Fredericksburg, Virginia
• Richmond, Virginia
• Petersburg, Virginia
• Roanoke Rapids, North Carolina
• Raleigh, North Carolina
• Cheraw, South Carolina on the Pee Dee River
• Columbia, South Carolina on the Congaree River
• Augusta, Georgia on the Savannah River
• Milledgeville, Georgia on the Oconee River
• Macon, Georgia on the Ocmulgee River
• Columbus, Georgia on the Chattahoochee River
• Auburn, Alabama
• Tuscaloosa, Alabama on the Black Warrior River

U.S. Highway 1 and Interstate 95 pass through many of these cities.

• Virginia Places website page on 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.

Alpine skiing fall line

In alpine skiing, a fall line refers to the line down a mountain or hill which is most directly downwards. This can be visualized as the route a ball would take if it were started rolling at the summit, and rolled to the bottom. This route (within the constraints of ski runs), is the optimal route down a run for a downhill skier.