Layers of Time Online Exhibit - Shell Midden

A shell heap or midden is a site where people lived and discarded food refuse such as clamshells and food bones, along with broken tools made of stone and bone. Over thousands of years, the middens built up—some to depths of many feet.

Shell middens are unique: they allow archaeologists to discover artifacts that don't survive at other types of sites. The shells, composed largely of calcium carbonate, reduce the acid in the soil, which helps preserve organic remains, such as burned plant materials and food bones. From these materials, archaeologists can determine the plants eaten, the animals hunted, the time of year people lived at the site and how people shaped bones into tools.