The story of South Carolina’s geography begins with the Appalachian Mountain chain. It’s in Appalachia where so much of the coast’s freshwater—in the form of rain—comes together and flows southeast—in the form of rivers—to the Atlantic Ocean. A feature called the Blue Ridge Escarpment, or “Blue Wall,” forms the demarcation point of the mountains, and its steep face is responsible for most of the many waterfalls in the state.

Moving east, the next level down from the Appalachians is the Piedmont region (in South Carolina often called simply the Upstate). The Piedmont is a rolling, hilly area, the eroded remains of an ancient mountain chain now long gone.

At the Piedmont’s eastern edge is the fall line, so named because it’s there where rivers make a drop toward the sea, generally becoming navigable. This slight but noticeable change in elevation—which actually marked the shoreline about 60 million years ago—not only encouraged trade, but has provided water power for mills for hundreds of years. Many inland cities of the region, like Columbia, trace their origin and commercial success to their strategic location on the fall line.

Around the fall line zone in the Upper Coastal Plain you can sometimes spot sandhills, usually only a few feet in elevation, generally thought to be the vestigial remains of primordial sand dunes and offshore sandbars. Well beyond the fall line and the sometimes nearly invisible sandhills lies the Lower Coastal Plain, gradually built up over a 150 million-year span by sedimentary runoff from the Appalachian Mountains, which were then as high or even higher than the modern-day Himalayas.

The Coastal Plain was sea bottom for much of the earth’s history, and in some eroded areas you can see dramatic proof of this in prehistoric shells, sharks’ teeth, and fossilized whale bones and oyster beds, often many miles inland. In some places, calcium from these ancient shells has provided a lush home for distinct groups of unique plants, called dijuncts.

At various times over the last 50 million years, the Coastal Plain has submerged, surfaced, and submerged again. At the height of the last major Ice Age, when global sea levels were very low, the east coast of North America extended out nearly 100 miles farther than the present shoreline. (We now call this former coastal region the continental shelf.) The Coastal Plain has been in roughly its current form for about the last 15,000 years.