An earth oven or cooking pit is one of the most simple and long-used cooking structures. At its simplest, an earth oven is simply a pit in the ground used to trap heat and bake or steam food. Earth ovens have been used in many places and cultures in the past, and the presence of such cooking pits is a key sign of human settlement often sought by archaeologists, and remain a common tool for cooking large quantities of food where no equipment is available.
To bake food, the fire is built, then allowed to burn down to a smolder, and the food is placed in the oven and covered (this can be used for bread-baking, for example, and has been used in some cultures for soldiers on military expeditions). Steaming is similar; fire-heated rocks in a pit are covered with green vegetation, large quantities of food, more green vegetation (and sometimes water), and then a final covering of earth. Food takes several hours to cook whether by dry or wet methods.
Today, many communities still use cooking pits, at least for ceremonial or celebratory occasions: the Hawaiian luau, Māori hāngi and the New England clam bake. The central Asian tandoor, used primarily for uncovered, live-fire baking, is a transitional design between the earth oven and the horizontal-plan masonry oven, essentially a permanent earth oven made out of clay or firebrick with a constantly burning, very hot fire in the bottom. In modern times, earth ovens are sometimes used for outdoor cooking and recreational meals in lieu of an open campfire.
The clambake, invented by Native Americans on the Atlantic seaboard and considered a traditional element of New England cuisine, traditionally uses a type of ad hoc earth oven (usually built in beach sand with heated rocks to retain heat and seaweed to add moisture) to cook shellfish and vegetables.
Earth oven cooking is sometimes used for celebratory cooking in North Africa, particularly Morocco; a whole lamb is cooked in an earth oven (called a tandir, etymologically related to the central Asian tandoor and possibly descended from an Akkadian word tinuru) in a manner similar to Hawaiian kalua pig. In Greek cuisine, there is also a tradition of kleftiko ("thief style") dishes, ascribed to anti-Turkish partisans during the Greek war for independence, which involve wrapping the food in clay and cooking in a covered pit, allegedly at first to avoid detection by Turkish forces.
Earth oven cooking was very common in the past and continues into the present - particularly for special occasions.
In the closely-related Polynesian languages the general term is "umu" or similar - the Tongan 'umu, Māori umu or hāngi, Hawaiian imu, Samoan 'umu, Cook Island umu. In non-Polynesian parts of the Pacific, languages are more diverse so each language has its own term - in Fiji it's a lovo and in Rotuman it's a koua. (In Papua New Guinea, "mumu" - borrowed from Polynesian, is used by Tok Pisin and English speakers, but each of the other hundreds of local languages has its own word.)
Despite the similarities, there are many differences in the details of preparation, their cultural significance and current usage.
The Samoan umu starts with a fire to heat rocks which have been tested by fire and which have not exploded. These rocks are used repeatedly but eventually are discarded and replaced when it is felt that they no longer hold enough heat. Once the rocks are hot enough they are stacked around the parcels of food which are wrapped in banana leaves or aluminium foil. Leaves are then placed over the assembly and the food is left to cook for a few hours until it is cooked.