Our 2025 programme of geological investigations gave the Green Volt team a fascinating insight into the complex Aberdeenshire geology along the onshore cable route. Supported by a team of experts and conducted in close consultation with landowners, the team worked to build a ground model of an area of previously sparse historical survey data and notoriously complex geology.
Understanding and verifying the geology that underlies the surface is vital to an infrastructure project like Green Volt. Given the onshore export cables will be buried underground, these surveys gather critical data that will inform the next stages of detailed design and development.
The site sits within a fascinating geological region, the Grampian Oregeny. The eastern part of the area is predominantly underlain with bedrock from the Crinan and Tayvallich subgroups, thick sequences of metamorphosed sedimentary rocks laid down more than 538 million years ago. Psammites, metamorphic sandstones, are predominant throughout the western part of the area.
Initial assessments along the onshore cable route corridor were made using geological record maps including the British Geological Survey (BGS) 1:50,000 map, and site-specific geological information. Despite useful records like those of the BGS, the area is one of relatively sparse historical data with limited borehole records and some historic mapping proving to be inaccurate.
One of the best sources of information in planning these investigations was perhaps the oldest form of geological data-gathering. The team talked to local landowners � including many who had worked the land for generations � to seek their first-hand experience of what lay beneath.
�Although we were working with a leading team of geological investigation experts, there were still a lot of unknowns in an area with less survey data than we might usually expect, and complex ground conditions."
Claire Gibson, Green Volt Land Manager
�This made our engagement with local landowners even more important. Discussions with those who have worked the land for generations helped to uncover insights we would never have found in the geological textbooks.
�It is a helpful reminder that, even when working on a cutting edge project like Green Volt, sometimes there is no substitute for the enduring art of conversation.�
This part of Aberdeenshire is home to some of the oldest rock formations on Earth, with rocks displaying multiple phases of volcanic and seismic activity. Each layer told a story of ancient upheaval and metamorphosis, as well as evidence of the glacial events that shaped the landscape.
Highlights of the work included finding some coarsely crystalline rocks, known as pegmatites, the presence of which was confirmed through conversations with academics at Durham University�s Earth Science department. These had initially been mis-recorded as weathered granite, as ancient faulting had altered the pegmatites to a state that could mislead even the most experienced site engineers.
Site investigation work along Green Volt�s onshore cable route
�Metamorphic rocks cover much of the region. However, the degree and type of metamorphism on display varied significantly, with spotted rocks (pelite with cordierite porphyroblasts) being identified sandwiched between massive psammites (sandstone), some of which were completely weathered and de-structured, and some of which were fresh and intact."
David Simpson, Principal Geotechnical Engineer at engineering consultancy Cundall, who supported the works
These discoveries reinforce the importance of approaching every site with rigorous site investigation and research. As we strive to progress the Green Volt project, our team are working to the highest standards, in order to deliver the world�s largest commercial-scale floating offshore windfarm.