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:
“I fellowed sleep who kissed me in the brain,
Let fall the tear of time; the sleeper’s eye,
Shifting to light, turned on me like a moon.”
—Dylan Thomas (1914–1953)
“Men are not to be told anything they might find too painful; the secret depths of human nature, the sordid physicalities, might overwhelm or damage them. For instance, men often faint at the sight of their own blood, to which they are not accustomed. For this reason you should never stand behind one in the line at the Red Cross donor clinic.”
—Margaret Atwood (b. 1939)