Cave Formations

Over the years, the water level in the Ruby Falls cave lowered, allowing air to enter. When that happened, the conditions were right for the creation of speleothems, or cave formations. Ruby Falls is perfect as a study for the different types of speleothems. Over the years stalactites and stalagmites have formed and some have grown all the way into full columns. In some sections of the cave, there are capillary tubes, drapery formations, and flowstones. Ruby Falls is a perfect way to experience the wonders of a cave and learn of their formations from experienced guides.

Speleothems (or cave formations) start their formation from events happening above the cave itself. Over years as rain falls through the soil above the cave. It mixes with the carbon within the soil to form a very diluted carbonic acid. This acid then seeps through the easily dissolvable limestone rock that is common in Tennessee and Georgia. The rainwater/carbonic acid moving through the limestone erodes the calcium carbonate bringing deposits of calcite with it through cracks in the limestone. As the water evaporates or drips into the cave, it leaves calcite behind, creating formations over a period of time.

Using Speleothems To Understand The Age Of A Cave

Speleothems can be dated to tell us how old the cave is. The age of a speleothem is affected by multiple variables: the amount of precipitation, the temperature inside and outside the cave, the amount of water moving through the cave, and the amount of carbon dioxide in the soil above the cave. If there is a lot of precipitation above the cave, the speleothem will form more quickly. Also if the cave continues to flood, the speleothem will be worn away and not have enough time to grow and build a cave formation.

Ruby falls is over 30 million years old, so our speleothems have had time to grow and form. We have stalactites, stalagmites, capillary tubes, columns, drapery formations, flowstone, and helictites! Keep an eye out for the following cave formations during your Ruby Falls tour!


Stalactites form as water drips from the ceiling of the cave, leaving minerals behind. The minerals build up very slowly to make the stalactite. All stalactites start out as capillary tubes (also called soda straws). You can always remember the difference between stalactites and stalagmites because stalactites hang "tight" to the ceiling.

Capillary Tubes

A capillary tube is a hollow stalactite. They are very thin and fragile. When the hole 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


We receive a lot of questions, one of those are always "how are stalagmites formed?" Stalagmites are formed when dripping water hits and deposits minerals on the cave floor. Over thousands of years, those mineral deposits build on top of each other, slowly growing the stalagmite higher and higher. Stalagmites are almost always found underneath stalactites and you can always remember the stalagmites hold "mighty" on the ground.


When a stalagmite and a stalactite grow towards each other over thousands of years, they will eventually meet and start forming a column. These columns will then widen as more minerals continue to drip down them.

Drapery Formations (Curtains)

Draperies, 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. They grow in any direction on the cave ceiling. Their twisted shape is attributed to air currents and the arrangement of the calcite crystals.