Regional geology is the geological study of large-scale regions. Usually, it encompasses multiple geological disciplines to piece together the history of an area. It is the geologic equivalent of regional geography. The size and the borders of each region are defined by geologically significant boundaries and by the occurrence of geologic processes. Examples of geologically significant boundaries are the interfingering facies change in sedimentary deposits when discussing a sedimentary basin system, or the leading or boundary thrust of an orogen.