Natural History

Natural History. . The geology and natural history of northwestern Alabama are defined primarily by two features: the Tennessee River, the Muscle Shoals, and Karst topography. Before the U.S. Army Corps of Engineers completed the Florence Canal in 1890, the Muscle Shoals, a shallow and rocky 40-mile stretch of the river, severely restricted Euro-American travel, trade, and navigation. These Sholas were not a singular mass. Instead, there were three main sections gapped by deepwater pools. The Elk River Shoals began just past Decatur and extended eight and a half miles to the mouth of the Elk River. The most extensive section, the Big Muscle Shoals, ran from the mouth of the Elk River fourteen and a half miles to Bainbridge Ferry. Finally, the Little Muscle Shoals spanned five and one-third of a mile from the bottom of the Big Muscle Shoals to Florence., Lamb's Ferry pool separated the Elk River Shoals from the Big Muscle Shoals. Further downstream, the Bainbridge pool separated the Big Muscle Shoals from the Little Muscle Shoals. These shoals developed when sand and sediment gradually accumulated into hardened formations along the riverbed., The Tennessee River Valley is also known for its Karst landscape and topography. A Karst landscape occurs when slightly acidic groundwater and river runoff seep into cracks in soft, soluble rock such as limestone, dolomite, or gypsum. The resulting dissolution of the surrounding stone creates numerous caves, underground springs, and sinkholes. An abundance of limestone caves and springs along the river make north Alabama an excellent example of Karstic processes in action., Captions , (Photo #1) Before the 1890s, the narrow and rocky Muscle Shoals made river travel notoriously tricky. This picture shows what the shoals looked like when water levels were low. (Courtesy of the University of North Alabama, Collier Library Archives and Special Collections.) , (Photo #2) This diagram kartic process-forming throuht dissolution of soluble rocks-in-action. The many limestone caves beneath the ground are characteristic of the Tennessee River Basin. (Courtesy of the Muscle Shoals National Heritage Area.) , (Photo #3) Vast stretches of the Tennessee River give way to intermittent rocky shores along the banks. This section of the river between Florence and Sheffield shows one of these gravelly slopes. (Courtesy of the University of North Alabama, Collier Library Archives and Special Collections.) , (Photo #4) When TVA constructed Pickwick Landing Dam in the 1930s, flooding created many reservoirs along the Tennessee River. Bluff Creek, pictured above, was one of these reservoirs. It's now called PickWick Lake. (Courtesy of the University of Alabama Museums.) , (Photo #5) Tennessee River banks are often steep and rocky. Thousands of years of geological bedding have produced walls of dense, stratified rock along the water. (Courtesy of the University of North Alabama, Collier Library Archives and Special Collections.)