During the Pleistocene Epoch -- between 2.5 million and 11,700 years ago -- the Tennessee River's base was at least twenty feet higher than it is today. Over thousands of years, however, the river's groundwater base gradually lowered toward its current height. As a result of this decrease, geologic features that had once been underwater caves now acted as springs, flushing water and sediment into the river. Today, north Alabama's many caves, springs, and steep canyons represent the Tennessee River's karst geology. Karst is a type of topography that occurs when water gradually dissolves soluble rock such as limestone, gypsum, or dolomite, creating empty spaces and ravines.
One of these rocky features, Dismals Canyon in Franklin County, has been designated a national natural landmark by the National Park Service. Dismals Canyon hosts a unique insect species, the Dismalite, a rare type of bioluminescent fly larvae more commonly known as a “glowworm.” This glowing insect exists in only two other habitats: Australia and New Zealand.
Key Cave National Wildlife Refuge is a similar byproduct of geological processes. A wildlife refuge in Lauderdale County, it’s managed by the US Fish and Wildlife Service. It encompasses many acres of grasslands but takes its name from an expansive limestone cavern that’s closed to the public due to its fragile ecosystem. The blind Alabama cavefish has been observed only in this single cave, making it one of the world’s rarest vertebrates. Gray bats also call the cave home. Their guano feeds tiny freshwater crustaceans, which the Alabama cavefish eats.
The Tennessee River offers plenty of opportunities for water recreation such as kayaking and fishing. But northwest Alabama’s woodlands and forests provide just as much recreational potential. The Muscle Shoals Reservation Trails appeal to hikers of any skill level with their wide variety of leisurely and challenging routes. Guests can view a waterfall at the base of Wilson Dam on the Waterfall Walk. Or, for those interested in a more difficult path, the forested Rockpile Trail offers a steeper climb. Millennia of geologic bedding and shifting landforms have resulted in an eclectic mix of hills and craggy valleys -- perfect for hiking. For more information on other trails, refer to the linked webpage for the Muscle Shoals Reservation Trails.
Visitors can also participate in mountain biking at Florence’s Wildwood Park or across the Muscle Shoals Reservation Trails on designated routes. Whatever the interest, there is something for everyone in the wilderness of northwest Alabama.