Geologic formation

In geology, a "Formation" is a formal named rock body. Formations are often named for the geographic area in which they were first described.

The term "formation" is often used informally to refer informally to a specific grouping of rocks, such as those encountered within a certain depth range in an oil well.

"Formation" is also used to describe the sometimes odd shapes (forms) that rocks acquire through erosional or depositional processes. Some well known cave formations include stalactites and stalagmites.