What are Archaeological Earthworks?
The Oxford Concise Dictionary of Archaeology defines earthworks as: ‘a general term describing any group of banks, ditches, mounds, scoops, hollows, platforms, or other structures of earth and stone’. However, they are often interpreted specifically as man-made changes in the surface of the earth. On a basic level, they frequently comprise either ditches or mounds of compacted soils which themselves are classed as archaeological features related to a specific function or previous event. However, earthworks can also form where there is a buried archaeological feature beneath the ground. Common examples include the foundations of demolished structures which produce mounds protruding from the existing ground level.
Are Earthworks Protected?
Earthworks are treated similarly to historic buildings – whilst some of them are of national significance and are protected by special legislation, others are considered to form more common types of archaeological evidence and are therefore subject to fewer restrictions. Those which are protected are termed Scheduled Monuments. Earthworks can also feature on local Historic Environment Records (HER) which are required to be consulted as part of planning applications. This is to ensure that new development limits or avoids any harmful impacts on these sites.
How are They Recorded?
Example of drawing conventions outlined by Historic England (2017)
Any kind of earthwork can be subject to detailed surveys. These aim to increase understandings of archaeologically-important sites to inform both future academic research and the sustainable management of these sites across the county. Protocols for recording have usefully been outlined by Historic England (2017) in a report titled Understanding the Archaeology of Landscapes. This document argues that analytical field surveys can provide a cost-effective means for recording earthworks using a small team and affordable equipment – thereby ensuring knowledge of the archaeological feature is not lost, even if they are to be affected by a development scheme. Field surveys are initially informed by a project design outlining clear aims and objectives for the investigations.
The key stages of earthwork surveys involve a reconnaissance, measured survey and finally, the depiction / digitisation of the results. Whilst some background research may be conducted prior to visiting the site, field reconnaissance - involving an in-person preliminary inspection of the site - provides a valuable initial assessment of areas of archaeological potential alongside the opportunity to deduce a survey strategy. A measured survey is then undertaken which can range from the use of standard tape measures to specialist equipment like total stations and GNSS readers to record a series of location points. When put together, these points can be used to graphically plot the archaeological earthwork to produce an accurate, measured drawing. Appropriate drawing conventions have been outlined by Historic England (2017). Special care is used to attempt to identify artificial changes in the earth (as opposed to the natural topography of the area) alongside chronological relationships between different archaeological features. A photographic record is also an essential step in recording the site. However, archaeological earthworks are not always easy to spot on photographs – something which itself highlights the immense value of measured earthwork surveys.
The level of recording required is dictated by the amount of detail required for the survey – something which ranges from Level 1 to Level 3. This is intricately linked to the perceived heritage value and importance of the earthwork.
Level 1: The least-intensive type of survey is Level 1. This often consists of rapid investigations of all of the earthworks present in a wider area - including summaries of the feature and a broad location plan at a scale of 1:10,000. Recording within this level of survey predominantly involves the creation of a photographic record instead of measured surveys.
Level 2: This level of survey requires a more detailed interpretive record of the site including metrically accurate archaeological surveys. This therefore requires a more detailed 1:2,500 plan in addition to a location plan at a scale of 1:10,000. Furthermore, these investigations also include detailed measured surveys representing the broad extent of the monument.
Level 3: This is the most detailed type of survey which involves precise recording of individual earthworks - including a detailed graphical plan of the feature which is recorded via a series of measurements taken on the ground. These surveys are also accompanied by reports involving more extensive and complex research into the feature and the surrounding landscape.
Example 1 : Ridge and Furrow
LiDAR data showing ridge and furrow from researchers at Cambridge University
Part of our team’s training with the University of York has included earthwork surveys of post-medieval ridge and furrow. These earthworks appear as large linear mounds and ditches represented on diagrams as dashes. Such archaeological remains are highly informative regarding the effects of continuous ploughing on the historic landscape. Much information can be obtained from the distance between the banks which relates to advancements in the machinery used to farm the landscape. Whilst some of the oldest surviving examples of ridge and furrow can be as far as 20 metres wide, more recent examples are frequently less than 5 metres wide. These earthworks were recorded on-site using tape and offset survey with the assistance of GNSS equipment. However, ridge and furrow can frequently be spotted on LiDAR data before even setting foot on site. Recent reports commissioned by Historic England (2020) have highlighted how the conservation of ridge and furrow is particularly considered to be at threat due to continued agricultural exploitation of these landscapes in addition to other modern interventions and developments. To aid understandings of these landscapes, a report has been prepared on historic field systems and land management – including the heritage significance of historic ridge and furrow.
Example 2: Barrows
The Normanton Down Barrow Group
An interesting type of earthwork interconnected with funerary archaeology is known as a barrow which consists of mounds of earth above one or more burials. These monuments formed focal parts of historic funerary landscapes and could often be seen from miles away. As such, they provide unique insights into how ancient peoples wished for their landscapes to be perceived. The most common types of barrows are round, oval, linear or square in shape. In England, they are also known as tumuli. These types of barrow earthworks have been outlined further in a report by Historic England (2018). A famous example has been found in Wiltshire and is known as the Normanton Down Barrow Group - a group of funerary monuments which are visible from the famous site of Stonehenge. The barrows date to the Bronze Age and many are subject to scheduled monument protection. The most famous barrow within this group is known as the Bush Barrow which dates to 1950 BC and contained the burial of a chieftain with numerous fascinating grave goods – including those fashioned out of gold - which are now housed in the Wiltshire Museum. The most famous find was a gold dagger pommel.
Gold details on the dagger pommel compared to the width of a needle
Want to know more?
If you have any questions about archaeological earthwork surveys, please get in touch with our team and we will gladly provide you with advice on your project!
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