Prof. Dr. Wolfgang Rabbel (IfG of CAU and Cluster ROOTS, in front) and students conduct seismic measurements on the Roman Iron Age dwelling mound Tofting. (photo: Jan Steffen, Cluster ROOTS)

How a seismic survey of an ancient dwelling mound works in theory is quickly explained. You produce a controlled seismic pulse in the ground, which is reflected differently by different layers and materials. Sensors on the surface pick up the reflections. The signals thus allow conclusions about the structure of the subsurface. But how does such a seismic survey succeed in practice when several colleagues as well as an entire herd of cattle is moving around on the same ground? A total of 25 students from the universities of Ghent, Vienna and Bratislava were able to learn this from August 29 to September 2 on the Eiderstedt Peninsula in Schleswig-Holstein. There, they took part in a joint research and training campaign of the Institute of Geosciences at Kiel University (CAU) and the Universities of Ghent, Vienna and Bratislava, which was funded by the Erasmus+ programme and supported by the Wadden Sea Project of the Cluster of Excellence ROOTS. In the process, the students used not only seismics but also other geophysical prospecting methods such as geomagnetics, electromagnetic induction (EMI) or drilling. "Each of the participating universities contributed their special methods: EMI equipment came from Ghent, for example, and seismics from Kiel," reports Prof. Dr Wolfgang Käppel from the IfG at CAU, one of the initiators of the campaign.

The work focused on the more than 1500-year-old dwelling mound Tofting on the southeastern edge of the Eiderstedt Marsh, as well as on the approximately 800-year-old dwelling mound row of Stolthusen in the present-day community of Katharinenheerd. "This covers two phases that are important in order to better understand the settlement of the sea-threatened west coast," says archaeologist Dr. Bente Majchczack, head of the Wadden Sea Project in the ROOTS Cluster of Excellence.

Tofting represents early settlement development during the Roman Iron Age, when people first created flat settlements on the edge of the marsh. Over the centuries, they piled higher and higher mounds under their farms to protect themselves from rising floods. "Albert Bantelmann already excavated parts of the Tofting mound in the early 1950s. Since then, however, nothing has happened there scientifically," explains Dr. Majchczack. Thanks to the new methods, he says, it is now possible to record the entire five-hectare terp without having to open up the ground again.

The row of terps in Stolthusen, in contrast, represents the high medieval settlement of the west coast in the 12th and 13th centuries, when people also cultivated the low-lying marshes. They systematically dug up moors, immediately built terps for their farms on the underlying soil, and divided the landscape into regular, narrow parcels of land. At the same time, they built the first dikes. "The procedure seems very planned. But many details are still unknown. Yet, we could perhaps learn something about how we deal with rising sea levels today from the behaviour back then," says Dr. Majchczack.

As part of the Cluster of Excellence, he has already studied similar settlement traces in the Wadden Sea. "These were the settlements that perished during the severe floods in the 14th and 17th centuries, despite all the protective measures. Rungholt is the best-known example in this context. In the current campaign, we are looking at the marsh settlements that have been preserved," explains the archaeologist.

While science thus gathers new information on how people coped with their lives in the face of a constant natural hazard, the students from Belgium, Austria and Slovakia learn the practical basics of geophysics in the field. For example, that as few metal objects as possible and no switched-on cell phones should be nearby when moving the two-wheeled cart with the geomagnetic sensors across a field. Or that even the footsteps of colleagues can be disturbing during seismic measurements. That's why a warning call is shouted before each measurement, whereupon all the other team members freeze for seconds, as if in a pantomime theatre. If necessary, an archaeologist must even become a herder to drive two dozen cattle away from the seismic measurement section. "Anyone who wants to do geophysical work later on as a scientist should learn about this practical work as early as possible. That's why it's good that we can carry out this extensive campaign with so many students," sums up Professor Dr. Wolfgang Rabbel from the Institute for Geosciences at Kiel University and as a co-spokesman of ROOTS.

The extensive scientific data obtained in the process now has to be evaluated. Results are expected to be available in a year.  
 
Link: The ROOTS Wadden Sea Project ‘Socio-environmental Interactions on the North Frisian Wadden Sea Coast’ 

Dr. Dennis Wilken from the IfG at CAU first explains what has to be taken into account for seismic measurements in practice. (photo: Jan Steffen, Cluster ROOTS)

Valentijn van Parys from Ghent University carries out electromagnetic interference (EMI) measurements near the Tofting mound. (photo: Jan Steffen, Cluster ROOTS)

Sarah Bäumler (CAU, centre), Valentina Laaha (Uni Wien, right) and Martina Hulmanova (Uni Wien) perform geomagnetic measurements. (photo: Jan Steffen, Cluster ROOTS)

Philippe de Smedt from Ghent University and Bente Majchczack (Cluster ROOTS) examine soil samples. (photo: Jan Steffen, Cluster ROOTS)

You don’t learn this in a lecture hall: when cattle interfere with seismic measurements, archaeologists sometimes have to act as herdsmen. (photo: Jan Steffen, Cluster ROOTS)