Columbus is located at the margin of the Coastal Plain and Piedmont
physiographic provinces (i.e., the Fall Line) of Georgia. The Piedmont
is composed of hard igneous and metamorphic rocks derived from the
recrystallization of ancient (300 to 600 million year old) sediments
that were once deeply buried and subjected to high
temperatures and pressures. They were re-exposed during
a collision between the African and North American Continents about
250 to 300 million years ago. The Coastal Plain is a wedge of
poorly-consolidated sand, clay, and limestone that thickens in a
coastward direction from Columbus. The sediments of the Coastal Plain
were deposited by ancient seas and river deltas that periodically
dominated the landmass over the last 120 million years.The location of Columbus is not by chance, but rather is the result of geologic conditions. The Chattahoochee River, which flows from Atlanta to the Gulf of Mexico, cannot incise a deep channel into the hard rocks of the Piedmont; consequently, the river bed is filled with shallow shoals impeding boat traffic. As the river crosses into the Coastal Plain, the current can easily erode the soft sediments from there to the coast, leaving a wide and deep channel. This geologic situation impeded northward river traffic of early settlers at the "Fall Line" and Columbus was born as a major business center.
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