is the best-known and most commonly used technique within the science of archaeology
. Individual excavations are normally referred to simply as "digs" by those who participate, this being an over-literal description of the process. An excavation concerns itself with a specific archaeological site or connected series of sites, and may be carried on over a number of years, since the work tends to be seasonal.
Within the practice of excavation, many more specialised techniques may be used, and each dig will have its particular features which may necessitate differences of approach. Resources do not allow archaeologists to carry out excavations whenever and wherever they choose; many known sites have been deliberately left unexcavated in the hope that improvements in technology will enable them to be re-examined at a later date, with more fruitful results. However, it is beginning to be predicted that the time will come when the process of excavation becomes completely redundant, as archaeologists will be able to make an assessment of what lies under the surface of a site without actually having to dig it up.
There are three basic types of archaeological excavation:
- Research excavation - when time and resources are available to excavate the site fully
- Rescue excavation - when time does not allow for a "proper" excavation, eg. when the site is threatened by building development
- Salvage excavation - when the site has already been damaged, eg. by erosion, time is extremely limited and the excavation becomes a damage limitation exercise
are collages made using a method developed in 1985
by Richard Genovese, in which pictures or images are glued together in layers, and then a layer or layers are ripped in places, revealing the underlying image.