A midden (also kitchen midden or shell heap) is an old dump for domestic waste which may consist of animal bone, human excrement, botanical material, vermin, shells, sherds, lithics (especially debitage), and other artifacts and ecofacts associated with past human occupation. The word is of Scandinavian via Middle English derivation, but is used by archaeologists worldwide to describe any kind of feature containing waste products relating to day-to-day human life. They may be convenient, single-use pits created by nomadic groups or long-term, designated dumps used by sedentary communities that accumulate over several generations.
These features, therefore, provide a useful resource for archaeologists who wish to study the diet and habits of past societies. Middens with damp, anaerobic conditions can even preserve organic remains in deposits as the debris of daily life are tossed on the pile. Each individual toss will contribute a different mix of materials depending upon the activity associated with that particular toss. During the course of deposition sedimentary material is deposited as well. Different mechanisms, from wind and water to animal digs, create a matrix which can also be analyzed to provide seasonal and climatic information. In some middens individual dumps of material can be discerned and analysed.
A shell midden or shell mound is an archaeological feature consisting mainly of mollusk shells. The Danish term kjökkenmöddings was first used to describe shell heaps and continues to be used by some researchers. A midden, by definition, contains the debris of human activity, and should not be confused with wind or tide created beach mounds. Some shell middens are processing remains: areas where aquatic resources were processed directly after harvest and prior to use or storage in a distant location. Some shell middens are directly associated with villages, as a designated village dump site. In other middens, the material is directly associated with a house in the village; each household would dump its garbage directly outside the house. In all cases, shell middens are extremely complex and very difficult to excavate fully and exactly. However, the fact that they contain a detailed record of what food was eaten or processed and many fragments of stone tools and household goods makes them invaluable objects of archaeological study.
Shells have a high calcium carbonate content, which tends to make the middens alkaline. This slows the normal rate of decay caused by soil acidity, leaving a relatively high proportion of organic material (food remnants, organic tools, clothing, human remains) available for archaeologists to find.
The archaeological study of shell middens began in Denmark in the latter half of the 19th century. The Danish word køkkenmødding (kitchen mound) is now used internationally. The English word "midden" (waste mound) derives from the Danish word mødding which in turn derives from møg (muck) and dynge (heap).