New 3D Electrical Map Sheds Light on Britain’s Deep Structure
A milestone in terrestrial geophysics arrives with Montiel-Álvarez and colleagues’ first 3D electrical resistivity model of Britain. Built from long-period magnetotelluric (MT) data collected across the island, the model—named BERM-2024—provides a high-resolution view of how electrically conductive and resistive rocks are arranged beneath Britain’s surface. By inferring the crust and upper mantle’s resistivity, the study highlights where igneous intrusions, sedimentary basins, and other geologic features lie hidden, complementing existing seismic and geological datasets.
What MT Data Can Tell Us About the Subsurface
Magnetotelluric surveys measure natural variations in electric and magnetic fields at Earth’s surface. From these measurements, researchers infer electrical resistivity, which varies with rock type, temperature, fluids, and mineralogy. In practice, MT can reveal conductive zones associated with fluids and melts, and resistive regions tied to dry, crystalline rocks. This information helps map subsurface features that are difficult to detect with conventional methods alone, such as deep intrusions, ancient fault zones, and crustal architecture that guides tectonic history.
BERM-2024: A First of Its Kind for the British Isles
The study synthesizes MT data from 69 sites across Britain, combining newly collected data with legacy measurements. A critical step in turning raw time-series records into a usable model was addressing the coastal effect—the ocean’s conductivity can distort electromagnetic signals during inversion. The team carefully corrected for this bias to ensure the resulting resistivity map reflects true subsurface structure rather than surface-water influences.
According to the authors, the 3D model resolves features down to depths of about 200 kilometers (125 miles). The resolution aligns with known structures from other surveys while also pointing to new anomalies that invite further investigation. Notable findings include highly conductive zones beneath Scotland’s Southern Uplands Terrane and a distinct resistive anomaly under Anglesey. Even more intriguing is a large, previously unknown conductive anomaly located between 85 and 140 kilometers (52–87 miles) beneath Britain’s West Midlands region. These features offer fresh clues about Britain’s tectonic and magmatic evolution and have potential implications for resource exploration and hazard assessment.
Linking Subsurface Structure to Space Weather Impacts
A standout aspect of the work is its demonstration that the resistivity model can forecast space weather effects. The researchers simulated the electric field at Britain’s surface during a notable solar storm that occurred on 10–11 October 2024, a period marked by vivid aurora displays across the Northern Hemisphere. The modeled surface electric-field time series showed strong agreement with actual observatory measurements, validating MT-based approaches for predicting geomagnetically induced currents (GICs) and related infrastructure risks. This bridging of deep Earth structure and near-Earth space weather exemplifies how comprehensive geophysical modeling can support critical planning for power grids, pipelines, and other sensitive networks.
Why This Matters for Science and Society
Beyond mapping Britain’s hidden geologies, the BERM-2024 model demonstrates the broader value of 3D resistivity approaches in planetary geophysics. By integrating MT data with robust inversion techniques, researchers can build more accurate pictures of the crust–mantle boundary, regional tectonics, and the distribution of conductive fluids. For space weather, such resistivity-informed forecasts offer a path to more reliable risk assessments and mitigation strategies, especially as electric-power infrastructure grows more complex and interdependent.
Looking Ahead
Montiel-Álvarez and colleagues’ work sets the stage for expanded MT deployments across Europe and other continents. Future campaigns could refine BERM-2024’s features, test additional solar-storm scenarios, and explore regional variations in resistivity tied to climate history and mineralogy. As 3D MT modeling matures, it will continue to be a valuable tool for geoscientists and policymakers alike, helping to illuminate the unseen architecture of our planet and its impact on modern life.
Source: Journal of Geophysical Research: Solid Earth, 2025. DOI: 10.1029/2025JB031813
