Beneath the surface at Bovbjerg Klint

Author: Maria Knadel

Bovbjerg Klint holds far more than meets the eye.

As part of EGN Week, Geopark Vestjylland is highlighting research at the geopark’s geosites. At Bovbjerg Klint, researchers have now taken a look beneath the surface.

Researchers from the HydroGeophysics Group at Aarhus University, in collaboration with the Central Denmark Region, have investigated the subsurface using modern geophysical measurements. The studies provide new knowledge about one of the geopark’s most important geosites and show how modern research can help add nuance to the story of how the landscape was formed.

To map the subsurface, the researchers used so-called geo-scanners. Some measurements were carried out on foot along the cliff, while a larger scanner was pulled across the fields behind Bovbjerg Lighthouse using an ATV. In this way, it is possible to obtain both detailed measurements close to the cliff and a broader overview of the area further inland.

“Using geophysical measurements, we can identify structures in the subsurface that are not visible in the cliff itself. The measurements provide us with a detailed picture of the soil layers and can help us understand how the layers continue beneath the surface and further inland,” says Line Meldgaard Madsen, Assistant Professor at Aarhus University, who leads the project.

A look into the subsurface

The method is based on electromagnetism. A transmitter coil sends a signal into the ground, and a receiver coil records the response from the subsurface. Along the way, the signal is affected by the electrical properties of the ground. Researchers can translate these variations into information about different soil types.

Clay and water-saturated layers conduct electricity well and have low electrical resistivity, while sand and dry sediments conduct electricity less effectively and have higher resistivity.

The result is a detailed image of the subsurface, where colours show variations in the soil layers. In the measured profiles, blue colours typically represent clay-rich deposits, while yellow and red colours indicate sandy layers.

Hidden structures at depth

While the cliff only reveals the uppermost layers, the geophysical measurements can provide insight into deeper structures hidden beneath the surface. Among other things, the researchers have identified a larger fault system north of the lighthouse – a zone where the layers of the earth have been displaced in relation to one another.

At the same time, the researchers are investigating whether the method can resolve the complex and often deformed layers visible in the cliff. These layers were folded and disturbed by the movements of the ice during the Ice Ages, and mapping their continuation down into the subsurface is a challenge.

In the next phase, the results from Bovbjerg Klint will be compared with previous geological mapping and detailed surveys of the cliff. The aim is to create an integrated model of the area’s geology. At the same time, the researchers will investigate the course of the Main Stationary Line from the coast and inland.

A geological backbone of the geopark

For the geopark, the research at Bovbjerg Klint is of particular significance. The cliff is one of the geopark’s most important geosites and also has international importance as a geological locality. In the layers of the cliff, the history of the landscape becomes visible, and local deposits point to broader geological connections in West Jutland.

A key element is the Main Stationary Line, which marks the maximum extent of the ice during the last Ice Age. At Bovbjerg Klint, a geological section through the deposits of the Main Stationary Line can be seen, providing special insight into the processes that have shaped the landscape of Geopark Vestjylland.

This is precisely why Bovbjerg Klint is an obvious place to focus attention during EGN Week, which highlights geopark geosites, research, and the knowledge that connects the landscape with both local stories and broader geological perspectives.

In this way, the research not only contributes new knowledge about what lies hidden beneath the surface, but also strengthens the story of one of the geopark’s most important geological landscapes.