Georgia is a beautiful showcase of the forces that are constantly reshaping the landscape. At the Atlantic shore, 14 barrier islands demonstrate some of these changes. We’ve had 4 Ice Ages in the past 2 million years, when ocean levels were low. The wind piled up large sand dunes at the coast. Some 6,000 years ago, the climate warmed and melting continental ice raised sea levels. Where the dunes were highest, they continued to stand out above the water. Today’s Cumberland Island, Sea Island and 12 others are the remnants of these dunes. Relentless wave action takes sand from one end of each island and moves it to the other end, making the islands migrate over time. The entire coastal plain is covered with sand, finely ground quartz that’s forever being moved around by water.
On a line connecting Columbus, Macon and Augusta, the image changes. North of the so-called Fall Line, which was once a beach front, the ancient rocks of the Piedmont have been squeezed and sheared for millions of years. Many roadcuts show folds in the bedrock. They illustrate how igneous rock, formed from a molten state, has been transformed into metamorphic rock by pressure and movement. Some hot bubbles of magma intruded into it and were later exposed by erosion, producing features like Stone Mountain.
Where limestone was squeezed hard, it turned into the beautiful white marble. There are few places like Tate, where even the local elementary school is built of marble. Here starts the Blue Ridge Region, characterized by a variety of metamorphic rocks, formed from the world’s oldest. The Blue Ridge, with peaks like Brasstown Bald and Blood Mountain, is a gorgeous example for a mountain range that was once as high as the Sierra Nevada. A drive along the Russell Scenic Highway (Ga.348 near Helen) offers views across mountain valleys as well as the Piedmont beyond.
In northwestern Georgia, past Chatsworth, begins the Ridge-and-Valley Province where one can see the limestone in its original 300-million-year-old shape. Sea lilies and other fossils show that it was formed by deposits on an ancient ocean floor near Chickamauga. Numerous caves in Walker County, some with pits hundreds of feet deep, have been carved out by flowing water. Altogether, the Ridge-and-Valley, the Blue Ridge Mountains, Piedmont, and Coastal Plain form a uniquely beautiful ensemble of natural history.
Rudi Kiefer, Ph.D., is a professor at Brenau University, teaching physical and health sciences on Brenau’s Georgia campuses and in China. His column appears Sundays and at gainesvilletimes.com.