The Embattled Wilderness: The Natural and Human History of Robinson Forest and the Fight for Its Future

CHAPTER 2 Ridgetops and Outcrops

28 C H A P T E R 2 Ridgetops and Outcrops James J. Krupa Robinson Forest is in a geological region known as the Cumberland Plateau, and in the Eastern Kentucky Coal Field, named for the layers of bituminous coal beneath the surface. The Cumberland Plateau runs along the western edge of the Appalachian Mountains from Kentucky, Virginia, and West Virginia down through Tennessee into Georgia and Alabama. The rock strata exposed in the plateau date back more than 320 million years and are tied to the formation of the Appalachian Mountains. Although old and weathered now, the Appalachians may once have been as impressive and imposing as the Himalayas are today. They were created in the Paleozoic era over a period of tens of millions of years as the continental plates underlying modern-day Europe, Africa, and South America pushed against the North American plate, causing the eastern edge of the North American plate to buckle and break. Some parts of the colliding plates were thrust up and over others to form a mountain range, an event that geologists call the Appalachian or Alleghanian Orogeny. It is amazing to think that these mountains formed before mammals and dinosaurs evolved. Flowering plants did not exist. Amphibians were the ruling vertebrates, and reptiles were just beginning their rise toward dominance. The higher and steeper mountains are, the faster they erode. Great volumes of sediment from the erosion of the western Appalachians flowed Ridgetops and Outcrops—29 west in ancient rivers toward a shallow inland sea. As sea levels rose and fell, the inland sea repeatedly advanced toward the Appalachians and then retreated back to the margin of the continent. For millions of years the region of the Cumberland Plateau alternated from shallow sea to coastal deltas and lagoons, to rivers and floodplains, to swamps and forests, and back again. Sediment from these varied environments accumulated in a subsiding basin west of the mountains that is known as the Appalachian Basin. When swamps covered the region, the Cumberland Plateau was hot and humid, lush and green. Ferns and horsetail rushes choked the ground, and scale trees (giant club mosses) and tree ferns filled the canopy above. The swamp water, highly acidic and lacking in oxygen, was hostile to microbial decomposers. When plants and trees died and sank or toppled into the water, they did not decompose as they would today. The dead vegetation slowly transformed into spongy brown peat instead. Sediment left by rivers, coastal deltas and shallow lagoons, and muds of the inland sea eventually covered the peat swamps. With pressure and time the peat transformed into bituminous coal; the coastal and delta sands became sandstone; and the floodplain, lagoon, and shallow sea muds became shale. Layer upon layer was deposited and buried in the subsiding basin as the inland sea advanced and retreated. The fossils from the ancient seas, coastlines, floodplains, and swamps found in the rock layers of the modern forest attest to the repeated advances and retreats. One can get a feel for what these swamps were like by visiting the Okefenokee Swamp in southern Georgia. Floating mats of peat form islands that cover the swamp and are home to water tupelos, swamp tupelos, and sweet gums. Hundred-foot-tall bald cypress and pond cypress trees tower over the islands. Shrubs such as cyrilia, buttonbush, fetterbush, and dahoon holly fill the understory. Spanish moss hangs from the trees, and water lilies fill the open water. The peat that lies beneath the Okefenokee makes the water acidic and stains it the color of tea. Trees fall and shrubs die, and they do not decay but transform into brown peat, just as the Paleozoic vegetation did in the Appalachian Basin. I have walked the tree islands of the Okefenokee. Even during the dry season they are a challenge to navigate. The peat is deep, soggy, and 30—Chapter 2 soft. Dead logs and tree branches litter the ground and are buried under the brown muck. What looks like firm ground can quickly transform into cold, wet ooze. I sank knee-deep, my legs scraped by buried, broken branches on the way down. One stumbles rather than walks over the floating peat. To explore the Okefenokee is to experience the Paleozoic swamps that once covered Robinson Forest. Of course, the plants were different, the creatures in the swamp were different, the climate was different , and the peat was...