Ruby Falls Geology
Lookout Mountain is widely known for its many unusual geological features. The most unique of which being Ruby Falls, a 145-foot underground waterfall located more than 1,120 feet beneath the mountain’s surface. The fascinating story of the formation of Lookout Mountain, the Ruby Falls cave and Ruby Falls itself is told by the rocks that formed each of these wonders.
Formation of Lookout Mountain
Formation of Ruby Falls Cave
- Carbon dioxide in the air is absorbed by rain water falling through it. The rain water also absorbs carbon dioxide that is in the soil after it hits the ground.
- Water breaks carbon dioxide down into a very weak acid called carbonic acid.
- The weak acid comes into contact with limestone rock when subterranean streams find their way through the cracks in the limestone rock that have been produced by tectonic forces.
- The acid solutes (or eats away) the limestone (which is made of calcium carbonate or calcite) causing the cracks to become larger and caves and passages to form. This process is called chemical weathering.
Formation of the Waterfall and Falls Room
Formations in the Cave
Over the years, the water level in the cave lowered and air entered the Ruby Falls Cave. When that happened, the conditions were right for the formation of speleothems, or cave formations. The formations process takes a very long time even though it is a very simple process – water moving through the soil absorbs the minerals in the limestone. As the water evaporates or drips, it leaves minerals behind.
Stalactites form as water drips from the ceiling leaving minerals behind. The minerals build up very slowly to make the stalactite. All stalactites start out as capillary tubes(also called soda straws). A capillary tube is a hollow stalactite. They are very thin and fragile. When the hold on the end of a capillary tube is closed off, it becomes a stalactite and begins to widen. Capillary tubes are very common in the Ruby Falls Cave, especially in the Hall of Dreams.
Stalagmites are formed by minerals deposited on the floor when the dripping water hits and leaves behind minerals. Stalagmites almost always form underneath stalactites.
Columns are formed when a stalactite and a stalagmite grow into each other.
Drapery formations (also called curtains) are formed as water works its way through the small cracks and crevices in the ceiling and evaporates before it has a chance to fall.
Flowstone is formed from flowing water instead of dripping water. The calcite is deposited in thin layers. These thin layers will first take the shape of the cave floor or bedrock beneath it. The flowstone builds up to become more rounded as it gets thicker.
Helictites are a type of stalactite. Helictites grow in any direction on the cave ceiling. Their twisted shape is attributed to air currents and the arrangement of the crystals of calcite.
- Cave Dwellers (troglobites) are those who spend their entire life in caves (ex. Blind cave fish or crawfish)
- Cave Guests (troglogenes) are those who use caves for shelter or hibernation but usually live above ground (ex. Bats, bears)
- Cave Lovers (troglophiles) are those that live most of their lives in caves. They are usually found near the entrance where some light filters in. They move back and forth from the outside to the inside as they search for food. (ex. Salamanders, Cave crickets)