Researchers have found new hints of active volcanism near some of the most populated areas of Europe. The study obtained GPS monitoring data from antennae across western Europe to monitor subtle movements in the Earth's surface believed to be caused by an increasing subsurface mantle plume.
The Eifel region is situated roughly between the cities of Aachen, Trier, and Koblenz, in west-central Germany. It is home to many early volcanic features, including the circular lakes called maars.
These are the remains of violent volcanic explosions, like the one which created Laacher See– the largest lake in the area. The eruption that produced this is believed to have happened some 13 000 years ago, with similar explosive strength to the catastrophic 1991 Mount Pinatubo eruption.
The mantle plume that possibly triggered this historic activity is thought to be still present, spreading up to 400 km (250 miles) down into the earth. However, it is unknown whether it is still active or not.
"Most scientists had assumed that volcanic activity in the Eifel was a thing of the past," said lead author, professor Corne Kreemer. "But connecting the dots, it seems clear that something is brewing underneath the heart of northwest Europe."
Eifel scenery. Image credit: Walter Koch/Wikimedia
In the new study, the research team who are based at the University of Nevada, Reno and the University of California, Los Angeles used information from thousands of commercial and state-owned GPS antennae all over western Europe to monitor how the ground is moving vertically and horizontally as the Earth's crust is stretched, sheared, and pushed.
The findings revealed that the region's land surface is moving in an upward and downward direction over a huge area centered on the Eifel, and areas including Luxembourg, eastern Belgium, and the southernmost province of the Netherlands, Limburg.
"The Eifel area is the only region in the study where the ground motion appeared significantly greater than expected," Kreemer stated. "The results indicate that a rising plume could explain the observed patterns and rate of ground movement."
The new results support a previous study that found seismic evidence of magma moving underneath the Laacher See– both studies indicate that the Eifel area has an active volcanic system.
"This does not mean that an explosion or earthquake is imminent, or even possible again in this area," the researchers noted.
"We and other scientists plan to continue monitoring the area using a variety of geophysical and geochemical techniques, in order to better understand and quantify any potential risks."
"Geodetic evidence for a buoyant mantle plume beneath the Eifel volcanic area, NW Europe" – Geophysical Journal International – Kreemer, C. et al. – DOI: 10.1093/gji/ggaa227
The volcanism of the Eifel volcanic field (EVF), in west-central Germany, is often considered an example of hotspot volcanism given its geochemical signature and the putative mantle plume imaged underneath. EVF's setting in a stable continental area provides a rare natural laboratory to image surface deformation and test the hypothesis of there being a thermally buoyant plume. Here we use Global Positioning System (GPS) data to robustly image vertical land motion (VLM) and horizontal strain rates over most of intraplate Europe. We find a spatially coherent positive VLM anomaly over an area much larger than the EVF and with a maximum uplift of ∼1 mm yr−1 at the EVF (when corrected for glacial isostatic adjustment). This rate is considerably higher than averaged over the Late-Quaternary. Over the same area that uplifts, we find significant horizontal extension surrounded by a radial pattern of shortening, a superposition that strongly suggests a common dynamic cause. Besides the Eifel, no other area in NW Europe shows significant positive VLM coupled with extensional strain rates, except for the much broader region of glacial isostatic adjustment. We refer to this 3-D deformation anomaly as the Eifel Anomaly. We also find an extensional strain rate anomaly near the Massif Central volcanic field surrounded by radial shortening, but we do not detect a significant positive VLM signal there. The fact that the Eifel Anomaly is located above the Eifel plume suggests that the plume causes the anomaly. Indeed, we show that buoyancy forces induced by the plume at the bottom of the lithosphere can explain this remarkable surface deformation. Plume-induced deformation can also explain the relatively high rate of regional seismicity, particularly along the Lower Rhine Embayment.
Featured image credit: Walter Koch/Wikimedia
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