How do archaeologists know where to dig?

‘So, how did you know to dig here?’ is by far one of the most common questions we get asked by people walking past or taking part in our excavations.

Archaeologists like us want to learn about how people lived in the past. Occasionally, that means excavating big, monumental sites that stand out in the landscape, like castles, burial mounds, or hillforts. But more often than not, the answers we seek are hidden among much more humble and subtle remains – the traces of homes, rural settlements and trading routes that truly tell us what life was like for the majority of the population.

So where do we dig? What seems like a simple or casual question is, to field archaeologists, a fundamental one that justifies our very existence. In actual fact, we probably spend more of our time considering where to dig than we do actually digging, and a two or three week excavation might be the result of weeks, months or even years of research and careful decision-making!

The thing is that as well as locating such sites, and deciding which of them to dig, we also have to decide exactly where to put our trenches; with limited time and resources, we rarely have the opportunity to dig an entire site and we have to be very strategic.

So, how do we do it? What are the factors we have to consider? And what are the processes we go through in order to decide not just which sites to dig, but exactly where to put our trenches?

The short answer is that it takes a combination of desk-based research, remote sensing, test-pitting, and careful consideration of a whole range of factors, from what our research goals are and how the site came to our attention, to what is logistically and ethically possible. Ultimately, it’s the question that justifies our very existence so let’s have a quick overview of some of the things we think about…

1. How did the site come to our attention?

The idea of excavating at a particular site, or within a certain area, might come about for a number of reasons. Maybe you’ve already been doing years of research across an entire landscape, or have been guided by a regional research framework. Perhaps it’s under some sort of threat, like coastal erosion, and you need to record as much of it as possible before it all gets washed away.

Perhaps you carried out a fieldwalking survey and spotted some unusual humps and bumps in the ground, or an unusual quantity of pottery on the surface. Maybe aerial images or cropmarks during a period of drought revealed previously unseen remains. Or maybe a metal detectorist discovered something interesting and reported it through the appropriate channels. But once the possibility of an excavation is on the table, you need to narrow it down – you can’t dig everywhere, you can’t dig forever, and where you dig will affect the results you get as well as the preservation of the remains themselves, so you need to make your decision extremely carefully.

2. What is already known about the site?

You might already know a lot, or almost nothing at all. Either way, a bit of desk-based research is definitely in order! You will almost always be able to find out more about your potential site; past or present. Some of the things you can think about may be:

  • What do local communities know?
  • Can you find anything out through comparing historic maps (or ‘map regression’)?
  • Are there any previous excavation or survey reports you can read through?
  • Is there any information about the site in the Historic Environment Record or local archive?
  • Were there any previous discoveries or surveys on your site (e.g., through metal detecting)?

3. What can we learn by remote sensing?

Once you’ve got a basic picture of what is already known about your site, you might be ready to start filling in some more details with a bit of remote sensing. There are so many techniques and processes that you can use nowadays that can tell us new information about a site without digging it. These are called non-intrusive investigations, or remote sensing. They include:

  • Aerial photography surveys (looking for cropmarks and earthworks)
  • LIDAR and topography surveys (building a 3D model of your site and the wider landscape to reveal any tell-tale lumps, bumps and surface features)
  • Geophysical survey techniques, like magnetometry, resistivity or radar (scanning the ground with highly sensitive equipment to give us an idea of what might be below the surface)
  • Fieldwalking (walking in transects across a site and recording the location of any surface finds to identify potential clusters)

4. What can you learn by intrusive surveys?

There are also a range of intrusive methods you can use to add more information to your understanding of the site, without opening up an entire trench. Boreholes or ‘auger surveys’ are a technique that allows environmental specialists and geoarchaeologists to investigate soils to impressive depths – without digging an enormous hole. Test Pits are also a technique that archaeologists use to investigate potential trench locations, and to assess the state of preservation. Both work a bit like biopsies, allowing archaeologists to get a sample of what exists in the ground across the site.

5. What are your research goals?

After completing your desk-based research and carrying out some remote sensing, non-intrusive surveys, or boreholes, you should have a pretty clear idea of what is already known about your potential site. Now comes the most important part of the whole process – identifying what you don’t know about your site.

What you don’t know is just as important as what you do know, and it’s the quest to provide new information that helps us justify why we dig, and exactly where we decide to dig.

A trench should always be placed in a location that you think can best answer specific questions that you have about your site. For example, if you’re main goal is to map the layout of a settlement, you might take a different approach than if your goal is to understand the chronology or different phases of occupation, and yet a different approach if you’re trying to understand how a particular part of it was used. So the next step? Review your list of questions that need answering, and define your research goals. These will also affect where you choose to dig.

6. Is digging the right answer?

Archaeology is a destructive process, and if you can answer your question without digging, you should. There are also lots of ethical questions that you really need to think about before you start. Are you allowed to? Do you have consent? The support of the community? And are you the right people, with the right expertise, to be doing it?

As well as legal and logistical considerations, the knowledge and preferences of the people and local communities living in and around your potential site also need to be at the heart of your decision. In the end, you might decide that the site is best left alone for now

7. Is there anything else you need to consider?

There are lots of other things that archaeologists need to consider too. Are there environmental protections? Or endangered species? Is it safe to dig? Can you actually get there? Do you need to make sure you’re not going to get washed away by the tide or blown off a clifftop by the wind?

Perhaps most importand of all, what resources do you actually have? What volume can you reasonably expect to excavate and record within the time you have available? And do you have enough post-excavation resources (i.e., laboratory and specialist support) to analyse and conserve everything you uncover?

8. So, how do we know where to dig?

DigVentures Lindisfarne

Our trenches in Sanctuary Close, immediately in front of the later Priory. Image Adam Stanford @Aerial-Cam

As you can see, where we dig is based on a whole series of factors, and on answering as many questions as you can before you start digging. Where your trenches physically go in the ground will be based on the results of your previous research. Your geophysics survey for example, might identify new features that you have specific questions about.

The more information you can get about your trench the better – and the more useful your trench is likely to be. Maybe, based on your geophysics, you think you’ve got a Roman Villa. But you don’t know its full layout or what date it is. Your trench could answer both questions by revealing structural remains that indicate layout and finds that give you a date.

Try it yourself

In 2018, we asked our followers to help us choose where to place our trenches at Coldingham, Scotland. Our aim was to assess whether this could be the location of an early medieval monastery led by Princess Aebbe and if so, what it’s state of preservation was and what we could learn about its history and how Aebbe’s nuns supported themselves. We narrowed the choices down to six potential trench locations, and asked our community to help us pick three. You can take a look at the options we laid out, see what everyone chose, and what we eventually found.

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Ben Swain

Written by Ben Swain

Ben is one of DigVentures awesome Community Archaeologists, who actually started as a Venturer! Originally an accountant, he dug with us every holiday. His enthusiasm and dedication meant we grabbed our first opportunity to hire him. He's now a professional archaeologist, who loves prehistory, Romans, and helping to train up other Venturers.

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