Exceptionally dry summer may reveal hidden archaeological monuments

While farmers have bemoaned this year's historically dry weather conditions, archaeologists might soon be reaping the benefits.

Have you ever wondered what secrets might lie just beneath the ground you are walking on? This year's drought might help shed some light on this question.

Archelogogists in England have already credited the exceptionally dry summer for an unusually bountiful harvest of so-called cropmarks. The dry soil has revealed a large number of ancient structures just beneath the surface, including buildings that haven't been seen in thousands of years.

Cropmarks become especially visible and form faster in parched soil, which means that this year could turn out to present a veritable treasure trove to aerial archaeologists in Luxembourg as well.

Even long after the buildings themselves have vanished from the face of the earth ... / © Historic England

Cropmarks reflect the surface beneath, making them extremely useful to archaeologists seeking to find ancient settlements and buried ruins. Negative cropmarks tend to appear above buried stone structures, such as walls, and channel water away from the plants above, leading the crops to under-develop or even dry out completely. The opposite is the case for a positive cropmark, which occurs when for example a ditch has been filled in with foreign soil. This leaves the plants above with more nutrients and they are visibly stronger than neighbouring plants.

... they can leave behind either "positive" or "negative" cropmarks. / © Historic England

Aerial archaeology in Luxembourg

The national archaeology research centre CNRA has kindly provided RTL Today with some information regarding cropmarks in Luxembourg. Their flying archaeologists occasionally perform aerial surveys, especially in the summer when the weather is clear and the soil is dry.

In 2017, aerial photos from Bonnevoie revealed V-shaped "redans", which are believed to stem from the French siege of 1684 by King Louis XIV. Rectangular shapes point to military camps. / © geoportail.lu

While CNRA's André Schoellen believes that this year's draught might have come a bit too late to reveal many cropmarks, he stated that they experienced exceptionally good results last year. This year's findings will only come out in a couple of months and might yet reveal some unexpected features.

The former front line can still be traced today. Several artillery "redoutes" from the second French siege in 1795 have also been discovered in the area. / © geoportail.lu

The CNRA rented a Cessna 172 along with an experienced pilot in late June and early July 2017. Despite the late flight date, they discovered a lot of known and unknown sites. In early 2018, the CNRA added a drone to its inventory, but it tends to be used for recording archaeological sites during excavation rather than for systematic aerial survey.

A map from the late 17th century shows the ditch, the triangular redans and several French camps (rectangular shaped boxes on the map) in the Bonnevoie area.

While the CNRA mount their own missions, they also work with the land registry and topography administration (ACT) which regularly maps the country and gives archaeologists useful tools. In 2017, the ACT's Orthophoto session revealed many new archaeological sites, much to the delight of the archaeologists at CNRA.

From more recent archaeological sites, such as line of siege of 1684 in Bonnevoie with a linear ditch, artillery positions and several camps, to ancient Roman villas in Echternach, Ermerange and Misärsbréck, and even an ancient fortified settlement in Pétange and prehistoric funerary structures in Pleitrange, the year 2017 gave archaeologists a lot of information to work with.

While archaeology is serious business for the most part, the CNRA's team of archaeologists sometimes stumble on more "creative" and modern cropmarks. In 2010, in a field close to Dudelange, a farmer decided to decorate her land in a very memorable way, even if her cropmarks have probably not withstood the ages.

No words needed. / © geoportail.lu