Geographical transition zones, also called regional boundary or boundary lines, separate nations, form social distinctions and divide political areas. Transition zones range widely in size and width. Some separate clearly distinct regions, while others serve as political or territorial markers with overlapping characteristics shared by people on both sides.
Politically, geographically and socially, transition zones serve as internal and external markers. Within countries, they distinguish members of different political groups, socioeconomic statuses and religious beliefs. These internal boundaries exist within city borders, delineate state boundaries and define national territories. In cities, they distinguish neighborhoods and suburbs. They also separate groups controlled by different governments and political leaders. Political boundaries sometimes share natural boundary lines, and change over time with changes in political leadership. While social and political boundary lines create artificial borders based on human societies, physical boundaries form based on natural landscapes and geography. Physically, boundary lines separate adjacent areas using landmarks like rivers, lakes and mountain ranges. These features divide states and form national borders for landlocked areas. Other natural landforms like straits and peninsulas, separate lands adjacent to water bodies. Although some boundary lines exist independently, others overlap. Social and economic boundaries, for instance, often merge. Divisions fall along political lines and often religious or economic lines too.