The distinction between a cave and a cavern involves geological specificity versus common linguistic practice. In everyday conversation, the two terms are frequently used interchangeably to describe any subterranean void. While both refer to natural openings beneath the Earth’s surface, the science of speleology—the study of caves—maintains a clear distinction. This difference is rooted in the process of formation and the presence of internal mineral deposits, or decorations.
Defining the Cave: The General Term
A cave is broadly defined as any natural void, chamber, or series of chambers in the Earth’s crust that is large enough for a human to enter. This is the general term encompassing all forms of subterranean openings, regardless of their origin or rock type.
Solutional caves, often called karst caves, are the most common type, created by the dissolution of soluble rock like limestone by naturally acidic groundwater. Other formations include sea caves, excavated by wave action along coastlines, and lava tubes, which form when the outer surface of a lava flow cools while the molten interior drains away.
Defining the Cavern: A Specific Geological Structure
A cavern, by contrast, is a term used to describe a specific type of chamber found within a larger cave system. The geological definition requires a cavern to be a large, hollowed-out space formed exclusively by the solution process in soluble rock, such as limestone. This formation involves slightly acidic water dissolving the rock over long periods, creating massive underground rooms.
A key feature that separates a cavern from a simple cave chamber is the presence of speleothems, which are secondary mineral deposits like stalactites and stalagmites. These formations occur after the chamber has been drained of water and filled with air, allowing dissolved calcium carbonate to precipitate. A cavern is therefore a solutional cave chamber that is decorated with these distinct mineral structures.
The Key Differences and Common Usage
The difference between a cave and a cavern lies in scope and specific features. A cave is the broad category, referring to the entire underground passage or system, regardless of its size or formation method. A cavern, however, is a more specific term, identifying an air-filled, typically large chamber within a solutional cave system characterized by the presence of speleothems.
For geologists, the distinction is based on process and decoration: a cavern is a decorated, solution-formed room, while a cave is the entire network or any undecorated void. This precise terminology is often lost in popular usage. The tourism industry frequently uses the word “cavern” to suggest a space that is particularly large or dramatic for marketing purposes. This commercial usage contributes significantly to the blurring of the scientific distinction.