Turtle Hill

A few notes about place

The state of Tennessee can be geologically divided into three adjacent regions. The eastern mountains, the central plateau and the western plains. During the Paleozoic, from 570 to 240 million years ago, a shallow tropical sea dominated the region. Life flourished in these waters. Forests of crinoids or sea-lillies, animals that looks plants, dominated the sea floor. Every hundred million years or so, the marine environment would yield to a phase of mountain building. As relentless as the convergence, faulting and skyward thrust, rainfall and streams continually worked to reduce peaks to lowlands so that most of the time the area remained underwater. The muds, silts, sands and river gravel eroding off the slopes spread out in the basins, eventually covering the primordial bedrock with a nine-mile thick layer of sediment.

On the plateau and mountains to the east, the tectonic-powered see-saw between terrestrial and submarine environments ended around 300 million years ago, when the dense rocks of Gondwana rammed into the ancient North American plate. In the east, massive sedimentary beds faulted and tilted skyward as the leading edge of Gondwana was driven under the lighter rocks of the continent where great heat and pressure catalyzed volcanic activity along plate boundaries. Unlike the radical angles of uplift still found in the Smokies, the deep sedimentary beds of the central plateau were gradually raised thousands of feet above sea level in a manner that maintained the original horizontal bedding. This was the third major orogeny in the past 250 million years. As South America rammed north from the Gulf, the horn of Africa smashed westward, creating a mountain range with peaks taller than today’s Rockies stretching from Maine to Texas. Time and water would slowly sculpt and soften the heights while the Cumberland, Harpeth and Duck Rivers and their tributaries worked through soft limestones in the heart of the plateau, hollowing out a central basin, encircled by a cuesta of resistant, crystalline sandstones. Where the escarpment is steep, there are waterfalls.

Previous orogenies had aggregated the proto-continent and erosion provided deltas and coastal plains. What distinguishes the Alleghanian Orogeny is being the first major uplift in the heart of the new supercontinent, Pangea. The Anti-Atlas Mountains of Morroco, the Appalachians, and the Ouachita Range in Arkansas are all relics from that time.

What is called the Cumberland or better yet, the Great Eastern Plateau of North America, is bordered to the east, south and west by the Tennessee River Valley and is geologically contiguous with the profiles of sedimentary beds found to the north in the 'Pennyroyal' area of Kentucky.

To the south, the highland rim is bisected into east and west by the Elk River, a major waterway draining the central plateau into the Tennessee valley in northern Alabama. After skirting the extreme southern rim of the central basin, the westernmost remnant of Elk Ridge extends one last highland across southern middle Tennessee. The dendritic drainage patterns on the western highland are as intensively lobed as those found throughout the plateau, although in more moderate relief. On a topographic map, the visual effect is like a mosaic of white oak leaves. In this sea of broken land, forested ridges and dark hollows, the rounded back of Turtle Hill rises in silence, overlooking a narrow valley tending south.

And where are you friend?