stratigraphic hierarchy

Stratigraphic hierarchy is a way scientists organize and understand layers of Earth’s materials. It starts with broad categories called "supergroups," which contain large sections of related rock layers. These break down into "groups," which are smaller yet still contain related layers, then into "formations"—distinct rock units recognizable in the field. Formations can be divided further into "members," the smallest units. This hierarchy helps geologists identify, compare, and study Earth's history by understanding how different layers relate in time and formation.