This line marks the 80 million year old coastline. Ocean levels gradually dropped as the area was uplifted and as the ice caps trapped more water. Many dune formations in south Georgia mark the shifting coastline as it moved toward the southeast. During the recent ice ages, so much water was used as ice that the Georgia coast extended out further than it does today. The region consists mostly of sands and clays that were washed down from the eroding Blue Ridge Mountains and the piedmont.
Limestone is the only rock found, particularly along the southwest portion of the state.
The most significant mineral mined in the area is kaolin.