In geology a bed is the smallest division of a geologic formation or stratigraphic rock series marked by well-defined divisional planes (bedding planes) separating it from layers above and below. A bed is the smallest lithostratigraphic unit, usually ranging in thickness from a centimeter to several meters and distinguishable from beds above and below it. The term is generally applied to sedimentary strata, but may also be used for volcanic flows or ash layers. This article includes a list of works cited but its sources remain unclear because it lacks in-text citations. ... A geologic formation is a formally named rock stratum or geological unit. ... Stratigraphy, a branch of geology, is basically the study of rock layers and layering (stratification). ... Two types of sedimentary rock: limey shale overlaid by limestone. ... Goldenville Strata exposed at a quarry in Bedford, Canada. ... This article is about volcanoes in geology. ... Ash plume from Mt Cleveland, a stratovolcano Diamond Head, a well-known backdrop to Waikiki in Hawaii, is an ash cone that solidified into tuff Volcanic ash consists of very fine rock and mineral particles less than 2 mm in diameter that are ejected from a volcanic vent. ...

In a quarry, a bedding is a term used for a structure occurring in granite and similar massive rocks that allows them to split in well-defined planes horizontally or parallel to the land surface. A small cinder quarry A dimension stone quarry A quarry is a type of open-pit mine from which rock or minerals are extracted. ...