While many important monuments have always been known about, if not understood, by succeeding generations (such as the pyramids of Egypt or Stonehenge) many buildings and sites from the past have vanished from posterity. This is a historical version of “out of sight, out of mind”. A significant number of such sites that were once lost have been rediscovered quite by accident, (such as the Lascaux caves in France), but there is also a systemic search for these places by archaeologists. If such places are not obvious to the naked eye, however, how do archaeologists go about finding them again?
Old documents can provide evidence of settlement or activity in the historical era, which archaeologists may then be able to track down. This can vary from maps of medieval towns indicating where buildings used to stand several centuries ago, to archaeologists in the Near East using the Bible to look for clues as to the whereabouts of places described in it. Heinrich Schliemann even used the writing of Homer to find the site of the ancient city of Troy, while the Viking sagas have led archaeologists to further sites such as l’Anse aux Meadows in Newfoundland.
Place names are another variety of written evidence that indicate past activity – and possibly archaeological remains to be found.
Salvage or rescue archaeology is a type of specialised work that comes from examining a site prior to development work taking place, and recording anything that is found before the building work continues. This usually applies to sites in historic urban areas because in long-standing cities such as London or York, where buildings have been built and rebuilt in the same areas over time, there is likely to be archaeology under the ground in most areas of ancient occupation. In England, the norm is currently for developer-funded work to take place to either rescue the site or to build damage-limiting foundations to preserve what it found for the future.
An example of an important site found by this approach is the Rose Theatre in London – although archaeologists knew the approximate location of Shakespeare’s playhouse, it was only when construction of an office block was underway that remains of the structure were found. The remains turned out to be far better preserved that anyone had expected, but as planning permission had already been granted the work went ahead with the site only becoming a Scheduled Ancient Monument after the construction had been completed.
Surveying a landscape can also help to detect new archaeological sites. Remains of activity visible to the eye – such as burial mounds, ridge and furrow plough marks or the walls of old buildings – indicate that these places were areas of human settlement in the past and could reveal further finds. Other sites are only visible on the surface as clusters of finds and may indicate if not a full settlement, certainly an area where humans used the landscape in the past (such as clusters of flint cores indicating the presence of an ancient flint-working industry on site). These scatters of artefacts could be picked up through fieldwalking across ploughed fields or through regional studies picking up patterns of activity over a wide area.
An example of this kind of work can be seen in the Thames Archaeological Survey in London.
Photographs from the air do not themselves reveal new sites – it is the interpretation of the pictures that is the crucial factor here. Experience is required to identify archaeological traces from marks left on the landscape by natural means (such as being able to differentiate a dried up river bed from and old road, for example). However, aerial photographs offer the opportunity to identify traces that would be difficult or impossible to see from ground level. This is particularly true of crop-marks and soil-marks, which are differences in the growth of crops or colour of soil caused by buried archaeological features. These features would be indistinguishable on the ground, but can form clear patterns from above if viewed under favourable circumstances (viewing crops during the growing season and in clear visibility, for example).
Drought circumstances can work in archaeologists’ favour to help reveal sites that wouldn’t otherwise be visible from the air, as parched landscapes can sometimes show soil-marks more clearly. The warm, dry weather of May and June 2010 helped to show archaeologists a previously unknown Roman fort near Bradford Abbas, Dorset, for instance.
The discovery of sites can be enhanced with the use of software to sharpen images and GIS to map the finds accurately back onto maps of the landscape so they can be found and explored further. Images from satellites (such as LANDSAT) have also been used to trace large-scale features in the landscape, such as levee systems from ancient Mesopotamia.
Renfrew, C and Bahn, P (1996). Archaeology: Theories, Methods and Practice. London: Thames and Hudson