"Cave formations" refers to the various shapes and structures that can be found inside caves, such as stalactites (hanging from the ceiling) and stalagmites (rising from the ground). Full definition
For example in the 1970 ′ s I made an advance in the theory of limestone cave formation because I am a chemist. (joannenova.com.au)
The rest of the cave remained intact, with minerals still able to produce new cave formations, which will take thousands of years to be completed. (taraletsanywhere.com)
This is a limestone cave formation filled with water that reflects an incredibly blue color - hence the name. (belizescuba.com)