Archaeology: More than just digging
Archaeologists study the evidence left behind by people in the past (not to be confused with palaeontologists, who study dinosaurs and fossils). In the UK, archaeologists are working to try to learn more about the period after the retreat of the last ice sheet, which occurred around 10,000 years ago in Scotland.
Much of the archaeology conducted in the UK today falls under the banner of commercial archaeology, taking place ahead of development. For example, if a new supermarket is being built, the developer is legally obliged to make sure they do not destroy any archaeology without record. Most councils employ an archaeologist who oversees these matters and decides what sort of work should be carried out in advance of or as mitigation for a development. Developers will employ a commercial archaeological unit to help them with this. A desk-based assessment (DBA) can be carried out on the chosen site before they start building: an archaeologist will look at old maps, written records and aerial photographs to assess the likelihood of the developer’s encountering any archaeology. If the likelihood of encountering archaeology is quite high, a developer might have to employ an archaeologist to watch the ground-breaking works to ensure no archaeology is uncovered and accidentally destroyed. Should something be discovered, it will be excavated and the results recorded before any development can continue. If there is known archaeology on a site, it will be excavated before building can start. All of this work is at the developer’s expense.
Some archaeological fieldwork takes place to preserve archaeology by record. For example, a site on the coast that is subject to erosion cannot necessarily be protected from the sea, but excavating it, recording what is found, publishing the results and learning as much as possible from the evidence will at least prevent it from disappearing without us ever knowing anything about it.
Other excavations take place purely for research purposes. Some community projects fall into this category, where the site is not in danger of being damaged, nor in an area of proposed development. In these cases, the site is being excavated purely so that we can learn about the people who built and used it in the past. At Mantle Walls however, the community project was put together in response to the damage being sustained to the site by the ploughing on the monument. Community projects are often designed around research questions aimed at finding out more about a site, with additional goals such as inspiring the local community and giving community members a chance to get involved in the heritage in their local area.
How do you know where to dig?
While excavations lead to many exciting discoveries, much archaeological work is non-invasive and is related to identifying and/or recording archaeological sites. One question that archaeologists are often asked is, “How do you know where to dig?” Often, archaeological sites have been known about for many years, even if they have never been excavated. Some sites are simply visible on the ground due to upstanding buildings or their remains. Others are identified when high concentrations of archaeological material have been discovered in an area, particularly in ploughed fields. Aerial photography allows for identification of sites through cropmarks: marks on the ground caused by changes in vegetation as a result of underlying archaeology (click HERE for an activity about cropmarks!) or shadows cast by slight changes in topogaphy, hard to distinguish from ground level but easier to see from the air when the sun is low and casting long shadows. Buried features can also be identified through geophysical survey techniques such as resistivity, ground-penetrating radar and magnetometry, which measure changes in the physical properties of the ground. Light Detection and Ranging (LiDAR) is a method of airborne laser scanning in which the ground surface can be mapped in 3D and new sites identified through careful analysis of slight changes in topography. Trees and vegetation can be digitally cleared from the resulting images, making LiDAR a really useful tool for identifying sites in areas with dense tree or plant cover. Some images below demonstrate what we can see through aerial photography and through LiDAR.
Excavation: Tools of the Trade
Archaeologists are often teased about getting their paintbrushes out to gently brush away little specks of dirt. The reality is very different – there is a lot of heavy work to be done! Mechanical diggers are sometimes used to remove the topsoil but the majority of the digging is done by hand. Mattocks (a bit like a blunt pick-axe, pictured top left) are use to break up soil if quick progress is required. Lighter work is done with a 4” trowel (pictured bottom left). The paintbrushes only come out for very delicate work – when cleaning the last traces of mud away from a skeleton, for example, or when excavating a fragile artefact. Garden sieves are sometimes used to carefully sift through loose soil to make sure no small finds have been missed.
Recording and interpreting finds
Artefacts discovered during excavation are carefully collected, bagged and recorded. Each find is carefully recorded, assigned an individual small find number, and placed into a zip-lock bag or protected in a suitable container if fragile.
Back in the lab, finds are cleaned, analysed and interpreted by an artefact specialist. Artefacts are assessed initially according to typology, a classification that makes it possible to identify and often date an artefact based on physical attributes. Some artefacts might be subject to further analysis: for example, we might send ceramic (pottery) sherds to a specialist who can identify what kind of vessel they came from and where in the world they were made. This can tell us a lot about the kind of site we are excavating.