Archaeological Methods: Excavation and Beyond - by Anna Henderson

Key words:

Archaeology- the study of human history through physical remains and excavation.

Excavation- systemically digging up an area or site.

Survey- analysis of a wide-ranging area.

Stratigraphy- the order and relative position of strata (layers within the ground).

Archaeology uses the physical remains of humans to study our history from the ancient world to today. Classical archaeology is hugely important to understanding antiquity as a whole, demonstrating the interdisciplinary nature of Classics. The first thing that comes to mind for most people when hearing the term ‘archaeology’ is excavation: systematically digging up a site to discover what remains. Whilst excavation is a key part of archaeology, there are several methods used by archaeologists that are not as well known, but are equally important.

One of the most important but often undersold methods in archaeology is the survey. Surveys can be used to examine a wide-ranging spread of land in a non-disruptive way. This is especially important because excavation is a destructive action. Archaeologists cannot replace the excavated site as it was. Surveys, on the other hand, do not destroy the area. Surveys originally began as a method to identify potential excavation sites. Archaeologists would use ancient sources to identify important areas and then would survey the land first to prove human interaction. However, today they are often used as valuable methods in their own right. One form of the survey is an aerial survey. This is when archaeologists take pictures of the ground from high up in the air, using drones or the very high-tech method of standing on a ladder. Aerial photography captures the entire site and often reveals tracks or lines left by previous humans that cannot be seen from the land. For example, a farmer’s field could have burrows across it as ancient sites often show traces of roads or large buildings. This technique is extremely helpful to identify potential sites but can also offer information by itself.

Another form of survey is field-walking. Archaeologists will literally walk across fields and pick up whatever objects they find lying on the ground. This may not sound very scientific, but often farming and construction works over the centuries mean that coins, pottery, tiles and glass are lying on the surface of the ground. If one area has a high concentration of pottery, then there was a lot of human activity there. This survey can offer information by itself: in the case of pottery, if diagnostic sherds (broken piece of a ceramic material) are picked up, for example, a lip, rim or neck of a vase, then archaeologists can identify the type and style of pottery that was used in the area. Field-walking can be high or low intensity and can cover either an extremely large area or a small one. It takes less time and is much cheaper than excavation.

Geophysical surveys are also a good method to identify sites. Using magnetometry, archaeologists can measure the patterns of magnetism in the soil. Anomalies or differences in the magnetic patterns usually mean there are burnt or metal remains or different types of rock. This usually indicates there was a previous human site there. Measuring electrical resistivity is another way to analyse soil without excavating. An electrical current is shot through the soil at intervals, which is translated into a map by a computer. Different electrical resistance indicates objects under the soil; if there is high resistivity, there could be stone, pottery or hollows of air. This method is helpful for identifying tombs and burials hidden under the ground, as the resistivity changes when the electric current encounters the space of air in the tomb.

Of course, surveys cannot provide extremely detailed information on a site; this is where excavation comes in. A good way to compare excavation and surveys is to think of excavation as a microscope and surveys as a telescope. They both offer different perspectives on the same area. Excavation can often seem like a treasure hunt; digging important objects out of the ground and displaying them in a museum. But excavations have to be conducted carefully in order to extract the most information. One of the key aspects of excavation is stratigraphy. When a site is occupied by humans, different levels of strata (layers) are created in the ground. This is usually due to the waste created by humans. Forms of strata can include construction layers and rubbish or lost items. By carefully watching the change in stratigraphy whilst digging, archaeologists can find out when a site was occupied. When sites are abandoned, there is often a layer of burnt materials from fires or rubble from demolition. When a site is unoccupied, there are layers of vegetation, silt and dirt.

A nicely neat stratigraphy at the edge of the excavation area in the Kerameikos Cemetery (Athens). Picture by Giovanni Dall'Orto, November 12 2009.

To date these layers, archaeologists usually rely on finds within the layers. Layers that are lower than others have to have been placed earlier than the ones on top. Any objects found within layers that we can date can therefore give approximate dates for the layers above and below them. The technical terms for this are terminus post quem and terminus ante quem. Terminus post quem is when a stratigraphical layer or object is later than an established date and ante quem is before the established date. Often, an exact date for sites and objects is impossible, especially as the sites get older, and so most dating is either given in a range or is approximate.

There are many different methods within archaeology that all give us different insights into the past. In an ideal world, archaeologists would combine these methods to create a wide picture of each site. However, archaeologists often have to choose which method is best suited to sites, considering expense, time and the geography of the site. What is most important is having clear research questions and goals to gain the most out of each method.

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