Ancient Volcanic Region in Germany Is Moving in an Unusual Way, Scientists Discover

An ancient volcanic region nestled between some of Europe's most densely populated areas may be reawakening, geologists have said.

According to a study published in the Geophysical Journal International, subtle, unusual movements in the Earth's surface indicate that the Eifel Volcanic Region in west-central Germany—located near the country's border with Belgium and Luxembourg—is not extinct.

This region has a long history of volcanic activity and is dotted with many ancient volcanic features, including low-relief craters known as "maars"—some of which are filled with water, forming circular lakes—that are the remnants of violent volcanic eruptions. The last eruption or explosion in the region is thought to have occurred around 11,000 years ago.

But while many scientists had assumed volcanic activity in the Eifel was a thing of the past, a handful of previous studies have hinted this may not be the case. For example, some of the maar lakes still release significant amounts of gas that some researchers think originates from the Earth's mantle—the geological layer below our planet's thin outer crust.

A paper published last year also found evidence of ongoing volcanic activity, with researchers detecting tiny earthquakes underneath the Laacher See, Germany—the largest maar lake in the area. The authors proposed that this seismic activity could be explained by the movement of fluids, possibly magma, in the lower parts of the Earth's crust.

The latest paper adds to this body of evidence: "Connecting the dots, it seems clear that something is brewing underneath the heart of northwest Europe," lead author, Corné Kreemer, from the University of Nevada, said in a statement.

Kreemer, who is originally from The Netherlands, became interested after making an accidental discovery while conducting research in his home country in 2016. He was attempting to use GPS data to map out how the land surface moves vertically and horizontally as a result of geological processes. During these investigations, he observed something unusual.

"I noticed that the southernmost part of the country went up considerably," he told Newsweek. "To investigate this more, I started gathering GPS data from the surrounding countries. The more I looked, the better I started to see this area of anomalous upward motion, and that this area was also [being] slowly pulled apart. I extended my scope to look at all of Europe—that is not part of the tectonic boundary around the Mediterranean Sea."

In the latest study, Kreemer and colleagues found that the land surface across a large area, centered on the Eifel region, but covering parts of Belgium, The Netherlands, France, and Luxembourg is moving upwards—or uplifting—which is unusual for most places in Europe, besides the Alps mountain range and Scandinavia.

"There were previous hints that the area has been going up, particularly in Belgium, but those studies were limited in scope and there was a lot of debate on what it meant; that is, were they seeing a regional signal or local instabilities," Kreemer said. "We used a lot more data that leaves no room for uncertainty. There is also evidence for uplift of geologic time-scales—about the last 800,000 years—but our results show that the area is uplifting much faster than it has done over those last 800,000 years."

According to Kreemer, the maximum uplift that they detected was 0.04 inches per year in the Eifel, which is "fast, geologically speaking." The researchers also found the land surface of the Eifel and surrounding regions that is uplifting is also stretching apart, which the researchers say is a "totally new finding."

"There is no other area in 'stable Europe' where we find coherent and significant uplift and stretching over a large area," Kreemer said.

Researchers say their observations of the surface motion could be explained by something called a mantle plume that is putting pressure on the land surface from below.

Mantle plumes are a proposed mechanism of heat transfer that deliver abnormally hot material in the Earth's mantle to the surface. Researchers have hypothesized these plumes are responsible for volcanic hotspots, like Hawaii, which are located far from tectonic plate boundaries where most volcanoes lie.

Laacher See, Germany
An aerial view of Laacher See, Germany. iStock

"The Earth is hot on the inside. As a result, the Earth's mantle convects; it is essentially a very slow version of a pot of boiling water. At some places material goes down, and at other places, warm material rises up," Kreemer said. "A mantle plume is a place where warmer material rises up. Because it is warmer, it is less dense, which makes it want to rise. Seismologists can sometimes see these plumes because seismic waves go slower when they travel through a plume."

Many seismologists suspect that there is a mantle plume located right beneath the Eiffel Volcanic Region that extends nearly 250 miles into the Earth and was likely responsible for the ancient volcanic activity in the area.

Whether this plume is still active or not has long been debated. However, Kreemer and colleagues say their results suggest that the plume is responsible for pushing the Earth's surface upward and outward in the area. "[The results] suggest that the mantle plume the seismologists see is actually buoyant; it wants to rise," Kreemer said. "That means that there continues to be warm mantle material close to the Earth's surface, which is a key ingredient to have volcanism.

"The plume itself is not made of magma, but it brings heat close to the Earth's surface, compared to other places. That heat then melts lower parts of the Earth's crust. The melt that is created is the magma, and it wants to rise through the crust to the surface. While the area seems 'dormant' now, future activity might be expected."

According to the researchers, their findings suggest that in the long-term there may be both an increased volcanic and seismic risk in this part of Europe, although they say the results do not mean that a volcanic eruption or earthquake is imminent, or even possible in the area again.

"Of course, if anything were to happen it would be catastrophic given that the area around the Eifel is so densely populated," Kreemer said.

"Our results have some implications for earthquakes. We already knew that there are various faults between the Eifel and the Netherlands and that these faults seem to have produced more earthquakes than other parts of 'stable Europe.' We now think why this is this case: the upward push of the plume pulls the crust apart and that would lead to earthquakes on those faults. I suspect that this will continue."

The researchers say that they and other scientists will continue monitoring the area using a variety of techniques in order to better understand any potential risks.

"In the past, volcanism in the Eifel consisted of violent explosions, which left these deep maar lakes. I am not a volcanologist, but I would expect that future eruptions would be similar in nature," Kreemer said. "The largest eruption/explosion that we know of—the Laacher See eruption of 13,000 years ago—produced six cubic kilometers of magma and 16 cubic kilometers of ash. That eruption can be compared to that of Mount Pinatubo in the Philippines in 1991."

Lijun Liu, an associate professor with the University of Illinois at Urbana-Champaign's Department of Geology, who was not involved in the latest study, told Newsweek that while it is hard to tell from the paper if the observations hint at a future volcanic eruption in the Eifel region, the work does make a "strong case" for a buoyant mantle plume under the area.

"In fact, this is the most vivid evidence I have seen that outlines the three-dimensional surface deformation above an upward moving mantle plume," Liu said. "Both the vertical surface motion and horizontal stress pattern corroborate the active plume beneath the surface. The model is consistent with other geological actives such as enhanced seismicity in the region. This study detects an important mantle power that is hidden from the surface landscape."

This article was updated to include comments from Lijun Liu.