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:
“Then one will say, ‘He is not dead, maybe,
Who was mortality’s unshaken lover
Who loved the spring upon the Tennessee,
The hushed fall and, again, the coming clover.’
None will recall, not knowing, the twisted roads
Where the mind wanders till the heart corrodes.”
—Allen Tate (1899–1979)
“For as the interposition of a rivulet, however small, will occasion the line of the phalanx to fluctuate, so any trifling disagreement will be the cause of seditions; but they will not so soon flow from anything else as from the disagreement between virtue and vice, and next to that between poverty and riches.”
—Aristotle (384–322 B.C.)