The dilemma faced by archaeologists
For many years, archaeologists had a choice: excavate or do nothing. Excavation involves manpower and equipment. It is expensive and it destroys the layers or ‘strata’ beneath the surface which are important for providing information about when archaeological finds were deposited. Once an area has been excavated, the scope for future archaeologists using as-yet-unforeseen techniques to discover more information is severely compromised. In the eighteenth and nineteenth centuries, many important archaeological sites were ruined or damaged by well-intentioned excavators, as well as robbers.
Early non-invasive survey methods
In recent years, a range of techniques has been developed for non-invasive surveying of known and potential archaeological sites. Our Society pioneered the use of an early technique – aerial photography – which allows subterranean structures such as walls and roads to be traced. These structures limit absorption of water by crops, resulting in visibly stunted growth and, in dry weather, parchmarks.
New geophysical techniques
Other non-invasive geophysical techniques such as ground penetrating radar and magnetometry allow archaeologists to discover important information about sites, such as whether the ground surface conceals ditches, pits, roads and masonry structures. They also enable archaeologists to pinpoint areas for selective excavation, saving time and money, and preserving other areas for future archaeologists to investigate.
Community Archaeology and Geophysics Group
Since 2013, the Society has participated in the use of several such techniques across important sites in Hertfordshire, through its partnership with the Community Archaeology and Geophysics Group. The Group is led by Dr Kris Lockyear, who is a lecturer at the Institute of Archaeology, UCL, Director of the Welwyn Archaeology Society, and a member of our Society. The photo below shows members of our Society and others in the course of a comprehensive survey of Verulamium, which was completed in 2019.
Although something was known of the layout of Verulamium before this comprehensive survey was completed, the survey enriched our knowledge of the city. One exciting find was the discovery of what may well have been a surface aqueduct supplying fresh water to the Roman city.