A fall line (or fall zone) is a geomorphologic unconformity (e.g., monoclinal faulting or flexing) 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.
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Famous quotes containing the words fall and/or line:
“In certain savage tribes in New Guinea, they put the old people up in the trees and shake them once a year in the spring; if they don’t fall out they let them live another year.”
—John Dos Passos (1896–1970)
“Expediency of literature, reason of literature, lawfulness of writing down a thought, is questioned; much is to say on both sides, and, while the fight waxes hot, thou, dearest scholar, stick to thy foolish task, add a line every hour, and between whiles add a line.”
—Ralph Waldo Emerson (1803–1882)