Beds are the layers of sedimentary rocks that are distinctly different from overlying and underlying subsequent beds of different sedimentary rocks. Layers of beds are called strata. They are formed from sedimentary rocks being deposited on the Earth's solid surface over long periods of time. The strata are layered in the same order that they were deposited, permitting discrimination as to which beds are younger and which ones are older (the law of superposition). The structure of a bed is determined by its bedding plane, the surface that separates two layers. Beds can be differentiated in various ways, such as by particle size or rock or mineral type. The term is generally applied to sedimentary strata, but may also be used for volcanic flows or ash layers. Types of beds include cross…