Monday, December 5

Drawing the map of a site without moving a grain of earth: the case of a hidden fort on the coast of Lugo

The Rueta castro, in the municipality of Cervo, on the coast of Lugo, is still underground, although the clearing of the undergrowth that covered the area has already revealed some of its structures. A team of archaeologists from the Higher Council for Scientific Research (CSIC) is analyzing what is hidden in that land, but it is not going to resort, at least for the moment, to the technique that is most commonly associated with these studies: excavation. For years, instruments have been used in this field to make a map of the ruins that have been buried “without moving a grain of earth”. The method is not unknown in Galicia, but its use has not yet spread.

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In this settlement, believed to be from the Iron Age and situated on a promontory above the sea, vegetation had grown. The owners of the land, currently divided into several parcels whose owners are private, had traditionally dedicated it to grazing or collecting plant species to fertilize other farmland. However, until a few weeks ago, the landscape was one of ferns and toxos. With the weeds cut down, the team of researchers, led by David González-Álvarez -from the Institute of Heritage Sciences- and Jesús García Sánchez -from the Mérida Institute of Archeology-, has used non-invasive methods to investigate what is under their feet. A georadar and a magnetometer offer information that they cross and interpret to determine where there are traces of human activity and what type they are.

González-Álvarez explains that with these techniques they look for underground anomalies, that is, alterations in the geological substrate that should be natural. The magnetometer detects very small changes in the Earth’s magnetism and indicates the presence of materials that are not the same as the surrounding environment. It is a device that archaeologists carry on foot in a backpack, so that it allows them to cover large areas of land in a short time. The images that are created do not, however, offer differences in depth. The georadar, which emits waves and captures the rebounds in the materials, does make it possible to establish whether or not the traces found are on the same level. With this information, the investigators can layer the elements and guess whether they have found a wall, a round house or other structures.

The main advantage of these techniques is, according to the archaeologist, that they allow the investigation of deposits without altering their preservation. Excavation, he adds, is a “destructive” method. Layers that are removed cannot be replaced and will not be accessible to anyone else. It is also cheaper and requires less effort to use these machines. In Rueta, he says to illustrate it, the team has investigated in a few days almost the entire extension with a magnetometer and large parts with georadar. Digging it all out “would probably take a lifetime of a team.” Non-invasive techniques also have “limitations”, he points out, and even if they improve, they will still not fully equate to digging up and being able to directly measure and see how structures are built.

Excavate (or not) all the deposits

This alternative gives strength to the debate on whether it is necessary to excavate all the ruins. In González-Álvarez’s opinion, it is an issue that archaeologists and institutions responsible for heritage should address “in the short term.” In addition to being a destructive technique, he considers digging up everything unfeasible due to the amount of heritage there is. But he adds that in recent years he has seen that many forts are being excavated with “short-term approaches” and “without being very clear about the scientific framework.” “And, more importantly, without knowing what the future management will be: who is going to keep it clean, who is going to take care of the minimum infrastructure so that it is understandable for the visitor or how the researchers are going to be able to squeeze the information,” he says.

The archaeologist defends exploring the possibilities of non-invasive techniques within the framework of this debate. In fact, the Rueta exploration has a training component for the researchers. The application of these strategies does not have a long tradition in Galicia and it is also “a way of gaining experience”, he points out. The decision to excavate has not been made and will depend on the discussion that opens when, in a couple of months, the conclusions of the study with the georadar and the magnetometer are ready. Without reaching that point, González-Álvarez says that what he is already clear about at this site is that it is necessary to keep the area clear of vegetation: “The good preservation of the structures makes it very understandable. Anyone arrives and identifies the system of moats and walls and recognizes traces that speak of their ancient occupation”. To prevent weed growth, he suggests that a neighbor’s flock graze the area.

Activity outside the walls

The castro has already been visited by children and adults from the area. Within the project, an opening towards the neighbors has been sought. The researcher explains that the origin of the investigation lies in the activity of the Mariña Patrimonio citizen group, which identifies places of interest and that they contacted this team of archaeologists because they knew they were developing this research strategy. This association obtained a subsidy of 5,000 euros from the Lugo Provincial Council for its activities and also managed to involve the Cervo City Council, which was in charge of clearing the land. The researchers’ response to this initiative could not be to “arrive like aliens” and stay away from the neighbors, explains González-Álvarez, who adds that the archaeological heritage usually provides opportunities to work with local communities because they are often places that they are in the collective memory and are referents. In the case of Rueta, he indicates that the neighbors knew that there was a castro and wondered what was underground.

The project has also come out of the walls of the settlement. The archaeologists are also investigating possible traces of activity outside the fortified enclosure, related to crops and livestock, an aspect to which the works have paid little attention so far.