The Lost Sea in Tennessee: America’s Largest Underground Lake


A vast cave system located in Monroe County, Tennessee, Craighead Caverns is home to “The Lost Sea of ​​Tennessee.” Stretching over more than 240 meters at the surface alone, this body of water is by far the largest underground lake in America and the second largest in the world! Although this fact attracts many tourists all year round, being enclosed in an intricate cave system, this lake offers quite a mysterious sight. Even with a glass vantage point for tourists, there’s a lot about this lost sea that isn’t obvious. So, let’s dive in to discover the largest underground lake in America!

Location and Geography of the Lost Sea

A map showing Tennessee and the location of the Craighead Caverns via Wikipedia

At the base of the Great Smoky Mountains between Sweetwater and Madisonville in Tennesee, The Lost Sea is located within the extensive Craighead Caverns cave system. The visible area of ​​the lake is 250 meters long and 67 meters wide with a known total area of ​​approximately 18,000 square meters. This makes Lost Sea the largest in the United States and the second largest non-subglacial subterranean lake in the world. That being said, the exact depth and area of ​​the lake is still up for debate, as many unexplored rooms in the water-filled caverns of Craighead have yet to be considered.

Other than that, the cave system is located in an area mostly made up of farmland closest to the town of Sweetwater, Tennessee. Reaching the lake from Sweetwater requires a short 10-15 minute drive along the new Highway 68.

Exploration and History of the Lost Sea

A Historic Moonshine Threshold Hidden in Craighead Caverns

Since the early 1900s, Craighead Caverns has seen a plethora of exploration to determine the features, size, and other characteristics of the cave system and lake. The Lost Sea itself was discovered in 1905 by a young boy named Ben Sands who found a small opening while playing in the cave system. Curious to know more, the boy entered an undiscovered room and, after throwing mud balls, found the surface of the vast Lost Sea lake. That being said, by the time he brought his father back, the lake had risen keeping him hidden until another exploration a few years later.

After its discovery, the lake gradually gained popularity, and in 1939 the fossilized remains of a Pleistocene jaguar were discovered in the cave system. However, the most important explorations undertaken in past centuries have involved modern equipment and divers, but even with this technology the end of the lake has yet to be found. A recent case involved a diver venturing into the depths of the lake with sonar and while able to map 13 acres of water, he was still running out of water all around him. Thus, it is believed that the actual extent of the Lost Sea may be much larger, but with its complex layout, it is quite difficult to be explored in depth.

Climate of the Lost Sea

Underground lake in Lost Sea Cave in Sweetwater Tennessee
Underground lake in Lost Sea Cave in Sweetwater Tennessee

Due to its depth of around 20 meters underground, the Lost Sea is protected from the local climate and tends to stay quite cold all year round. In most areas, the average lake water temperature is estimated at 13°C. While most of the region is in a humid subtropical climatic zone according to the Koppen classification, variations in temperature affect Craighead Caverns to a minimum, providing a somewhat static climate all year round.

Geology and ecology in the lost sea

Crystal formation in Craighead Caverns

Although it may be located far below ground level, the Lost Sea and the Craighead Caverns surrounding it are still home to various unique rock formations and also support organic life. Mainly, the cave system is well known for a wide range of crystal clusters such as stalactites, stalagmites, etc. which come in unique spike-like shapes through the walls. For example, many anthrodites caused by iron drained from the rocks are visible from the ceiling of the cave. In total, the Lost Sea is believed to host 50% of the world’s known aphrodite formations.

In terms of the ecology of the Lost Sea, the body of water is primarily the habitat of a single species of fish, the rainbow trout. These trout can be seen swimming along the upper levels of the lake, and a total of 300 are estimated to live in the lake. As the water itself is quite clear, these rainbow trout are often seen near tourist viewpoints and swimming near boats.

Tourism and recreation in the lost sea

Due to factors such as its unknown depths, beautiful aesthetics, and position as one of the largest underground lakes in the world, the Lost Sea has quickly become a famous tourist spot in the state. With around 150,000 tourists every year, the area has been developed with a tourist center above ground, a long walkway down below, and even activities in the cave.

Some of the most enjoyable things to do are gazing at the beautiful rock formations and rainbow trout via the glass viewpoint or even taking a boat ride on the lake and dipping your hand in the water cold. For people who don’t want to take the boat tour, a one-hour tour is also available with an experienced guide so you can take in all the fantastic rock formations and mysterious beauty of The Lost Sea in Tennessee.

Whatever you may enjoy, one thing is for sure, the real thrill of this lake lies in its unknown depths and if we ever really find its limits.


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