The problem with metal detectors

Archaeology is a science that studies past societies based on their material remains. And, although prospecting is increasingly important as a method of study (see the corresponding post, entitled Prospecting as an alternative to excavation), excavation remains the most representative activity and the one that provides the most information.

However, everything comes at a cost. In Archaeology, excavation involves the destruction of the stratigraphic record of what is extracted. But what is the stratigraphic record? Why is it so important?

Archaeological sites are composed of different layers or strata, generally horizontally aligned, that together form a sequence. The first layers are located in the lower part, and little by little new ones are being superimposed to date. Thus, the lower part is usually older than the upper part, although there are exceptions, as is the case with pits.

The archaeological excavation seeks an exhaustive documentation of everything found, although it also causes the destruction of that record; an archaeological site can never be restored to its previous state and, therefore, the information contained in the layers that has not been documented will be lost forever. That is why it is very important that the excavation be planned with an appropriate project and methodology, and always by qualified and experienced personnel.

And that is why it is equally important to control tools that can cause serious damage to the Historical Heritage, one of the most controversial being the metal detector.

A metal detector emits electromagnetic pulses that, when it encounters metallic materials, returns a signal to the device, which informs the operator of this by means of an acoustic signal. Therefore, the use of the metal detector by itself is a non-invasive technique that does not harm heritage, it simply provides information about the existence of a metal in a specific place, with its type (iron, lead, silver, etc.), approximate size and depth.

The problem is the excavation immediately after use to remove the metal. Doing so partially destroys the record, that succession of layers that we were seeing. In addition, “detectorists” do not usually document the context, the information associated with the object that provides it with a large part of its value (stratum to which it belongs, position of the object, state of conservation, if it is associated with any constructive structure, if there is more archaeological material nearby...), so that information is lost forever and we talk about the object being decontextualized.

With all this, it is inevitable to ask yourself a question: is its use allowed? The answer is similar to many other questions: it depends.

In Spain, the Law 16/1985, of 26 June, of Spanish Historical Heritage, regulates everything related to our Historical Heritage. However, in most cases it is the Autonomous Communities who, in accordance with the Constitution, manage what is related to their Cultural Heritage. To this end, they have developed their own laws on heritage, more up-to-date and extensive, in order to safeguard it.

In Andalusia said Law is 14/2007, of November 26, of the Historical Heritage of Andalusia, whose art. 60 of Title V is called “Authorization for the use of detectors and other instruments”. It states the following:

1. The use of metal detectors or other tools or techniques to locate archaeological remains, even if this is not their purpose, must be authorized by the Department responsible for historical heritage. Uses established by regulations may be exempted from this authorization.

In addition, prohibitions on these uses will be established by regulations.

[...]

However, since 2018, there has been a Preliminary Bill to amend this Act pending approval. One of the great novelties it incorporates precisely has to do with metal detectors. Thus, point VI of the Explanatory Memorandum states that”This Act provides for the prohibition of the use of metal detectors, except in cases where their use is contemplated in a regulated archaeological activity or is linked to activities that have nothing to do with the possible detection of archaeological or mineral remains, such as works or actions for maintenance, repair of infrastructure and facilities or other similar ones determined by regulation, as well as all those related to the Security Forces and Bodies and to the National Defense”.

In other words, we move from the current situation, in which its use is allowed as long as authorized by the Ministry of Tourism, Culture and Sports (or the competent one, if any), to a future more restrictive approach, in which by default it will be prohibited with exceptions.

This scenario will allow greater protection of the Historical Heritage, and in this line the applicable regulations must be guided. It is also desirable to tighten economic and/or criminal sanctions for the indiscriminate use of this tool. But the most effective thing is, without a doubt, education.

Education to transmit the importance of this heritage, which belongs to all of society, not just to those who find it. Because, apart from being a first-rate tourist resource, Heritage helps us understand our past. A single ring, coin or brooch seems insignificant, although, as stated previously, with this element the context that surrounds it is also lost, and which may be the key to understanding other larger and more complex political, economic, social, urban... circumstances of a site.

Therefore, at the legislative level, its regulation depends on the Autonomous Community in which we are located, although it has limitations of use in many cases. And at a technical level, it can be considered a restricted instrument, useful as long as it is properly integrated into a research project and is used by qualified and experienced personnel, but potentially dangerous in other situations.

By its very nature, it has recently been used for the investigation of various ancient war events. An example is found in the Iberian city of The liturgians (Mengíbar, Jaén), which was besieged and destroyed by Scipio Africanus in 206 BC as part of the Second Punic War (218-202 BC), due to the betrayal suffered by the Roman general. This project made it possible not only to rethink the traditional location of the city, but also to know in an exhaustive way the development of the siege itself.

Another somewhat later siege, but also confronting Iberians and Romans, specifically related to the Sertorian Wars (82-72 BC), is that of Cabezo de Alcalá de Azaila (Teruel). This project, still in an incipient phase, has demonstrated the enormous potential of the deposit thanks in part to metal detectors, used by experts and in a controlled manner.

And, finally, a somewhat recurring question: what happens if we find some archaeological element by chance? In this situation, we must call the Provincial Museum corresponding to the municipality of the discovery and from there they will be responsible for explaining the procedure to us, although as a general rule, the most convenient thing is not to move the piece and wait for archaeological personnel to remove it from the Museum. If it were absolutely necessary to do so, we must first photograph it in order to document its original state and place of appearance.

Bibliography

Bellón Ruiz, J.P., Lechuga Chica, M.Á. , et al. (2021) . ”De situ Iliturgi, archaeological analysis of their siege in the context of the Second Punic War”. Spanish Archaeology Archive, 94, and 15. DOI: https://doi.org/10.3989/aespa.094.021.15

Romeo Marugán, F. (2021): “The offensive system and battlefield surrounding the old town of Cabezo de Alcalá de Azaila (Teruel). First results”. Gladius, 41:67-89. DOI: https://doi.org/10.3989/gladius.2021.04

Cover photo: Baecula Project. Institute of Iberian Archaeology, University of Jaén.

Juan Antonio Moral, Archaeology