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Volcanic activity: Moving magma at Lake Laach

Volcanic activity : Moving magma at Lake Laach

Satellite images show that the earth is rising in the Eifel village of Glees. Further measurements suggest that the magma chamber of the volcano at Lake Laach is slowly filling up again. Is an eruption now imminent? An expert explains what the data means - and what they don't.

In the Eifel village of Glees near Lake Laach, the earth is rising. Around one centimetre per year, the ground pushes upwards at one point. This is shown by satellite images from the German Soil Movement Service (BBD). With the help of radar technology, two Sentinel-1 satellites measure from an altitude of 700 kilometres whether the ground is rising or sinking; roofs are the most common measuring points for this. The Federal Institute for Geosciences and Natural Resources recently started visualising this data on a map that can be accessed online. Where the earth is sinking - classically, for example, where mining is taking place - the aerial photographs are full of red and yellow dots. Where it rises, blue dots shine.

Around the Eifel village of Glees there are green dots. These mean that the earth's height has not changed there. Only in the north of Glees are there first turquoise, then darker ones, and at an address at Wiesenhof a deep blue dot in the middle of a roof. This means an increase of almost four centimetres between 2016 and 2019.

The roof belongs to a building covering the well of the mineral water producer Sol Kohlensäure GmbH. A recent article on the news portal t-online says: "Strange things are happening in the Eifel village of Glees. The earth shakes slightly, the earth rises slightly, and it no longer bubbles in the well at Sol Kohlensäure GmbH: after around 50 years, no more carbonic acid has been coming out of the depths since 2016. No one really knows what this is connected to, but one thing unites all the phenomena there: the place sits above the Eifel volcano."

There are signs that magma has started to move under the volcanic area and that the magma chamber of the Laacher See volcano is slowly filling up again. However, a connection to the uplift, for which no one seems to quite have an explanation, is by no means clear. And the matter of the dried-up carbonic acid spring also seems to have come to a head.

Spring in Glees has been supplying less carbonic acid for some years now

"That is not correct," says Mario Čurčić, managing director of Sol Kohlensäure GmbH, which among other things operates said well in Glees. "What is correct is that less carbonic acid has been rising at this location for years. The spring is about 60 years old. It is not unusual for a natural spring to dry up after decades," he explains. "That's just geology.“

Čurčić does not want to give exact details on how much the amount of rising carbonic acid has reduced. Only this much: "We are talking about several thousand tonnes per year that are extracted from the wells." At the well in Glees, where the uplift was measured, "slightly less" carbonic acid is now rising to the top.

The well is currently at a standstill because it is being overhauled so that it can continue to produce carbonic acid there in the future. "We pump through a perforated pipeline that runs through rock and earth about 500 metres down. This becomes clogged over time and then has to be cleaned or removed. That's the reason the well is at a standstill right now - not tectonic or volcanic movements.“

Expert: „The whole Eifel is rising slightly - we are monitoring it“

Georg Wieber is also not panicking in view of the carbonic spring. Wieber is head of the Rhineland-Palatinate State Office for Geology and Mining in Mainz and explains when asked: "Yes, something is happening. But the fact that the earth is lifting can have various reasons. According to our findings, the well in Glees is probably simply getting on in years and can no longer be operated.“

That the earth rises is normal, he said. "The whole Eifel region rises slightly. Here, the ground moves by a few millimetres per year. These are very small movements that should not cause panic. In Iceland or around Naples, we sometimes talk about ground heave of several decimetres per year. But of course we have the regional heave monitored." Because an uplift like the one in Glees is quite unusual, he says. "But there can also be man-made causes behind it," he explains, citing the decommissioning of the well system or a rising groundwater level as possible causes.

Nevertheless, it is likely that magma is rising underneath Glee. There are certain indications of this, such as "very weak quakes that have only been measurable for a few years," Wieber knows. "These so-called DLF quakes (editor's note: deep low-frequency earthquakes) are due to volcanic material, i.e. magma or hot water, rising and thus leading to tensions in the earth's crust.“

A 2019 study detected eight such quakes since 2013 at depths ranging from 10 to 45 kilometres. Scientists interpret this as a sign that the volcano is still active and that the magma chamber is currently being filled by rising magma.

Magma (is) rising at Lake Laach - is a volcanic eruption now imminent?

When a layperson imagines that magma is rising again in a volcano, the idea of an imminent catastrophic eruption quickly resonates. Wieber, however, can reassure: "The activity around Lake Laach is being studied by various scientific institutions. The consensus opinion is that no eruption is to be expected in the near future." Nevertheless, experts assume that the Laacher See volcano will erupt again within the next one million years.

That is, of course, a long time. But how exactly could an eruption be predicted in the first place? That depends, among other things, on the type of eruption, Wieber explains. The last time it happened, 12,900 years ago, it was a so-called phreatomagmatic explosion, triggered by magma reacting with water. Huge streams of embers were ejected, volcanic ash and pumice covered the area towards the Rhine valley up to seven metres thick and dammed the Rhine upstream to form a lake landscape. At that time, ash clouds travelled as far as Sweden and northern Italy. "Normal volcanic eruptions are much slower. Think of Mount Etna in Sicily, where lava keeps coming out in slow streams," says Wieber.

Investigation methods around Lake Laach are being expanded

The investigation methods around Lake Laach are currently being expanded. Wieber explains: "There are three ways of tracking magmatic activity - in other words, everything connected with an eruption: We observe the surface, the earthquakes as well as the composition of outflowing gases. For the Eastern Eifel, we have developed a monitoring concept that covers all three areas. It just needs to be implemented now."

The Earthquake Service South-West monitors earthquakes in the vicinity of Lake Laach. "With earthquakes, there are two different types," Wieber explains. "Tectonic quakes, that is when rock layers move past each other, and the volcanic DLF quakes, which are relevant in this case." South of the Laacher See volcano begins the so-called Ochtendung fault, a deep tectonic fault that extends from north-west to south-east near the village of Ochtendung. "Quakes occur comparatively frequently on it, sometimes somewhat stronger ones," Wieber explains, "but these are tectonic quakes.“

Surveying the earth's surface is also important for earthquake monitoring. Up to now, this was done every few years from the air, and the State Surveyor's Office could then calculate differences. Recently, the measurement has taken place via satellite, operated by the Ground Motion Service Germany (BBD). "The method is completely new. We are now in the process of permanently installing this measurement data. That costs money, of course, but we want to establish that the data is delivered to us every three days - that is, whenever the satellite flies over the Eifel."

A volcanic eruption in the Eifel cannot be predicted with complete accuracy

The State Office for Geology has also newly established gas investigations. "CO2 rises in many places in the Eifel, it comes from volcanism and is also the basis for the mineral water industry. The bubbling at Lake Laach is caused by escaping CO2, and the geyser in Andernach is also driven by it. But what's most interesting for us are the helium gases it contains." Helium is a noble gas that forms various isotopes. This means that the atomic nuclei of an element have the same number of protons but a different number of neutrons. "The helium that rises from the Earth's crust has a different signature than that from the deeper mantle," Wieber says. "These measurements are very complex and have to be repeated several times to obtain comparative values. The University of Bremen has just started doing this. The next measurement will be taken in three months.“

Nevertheless, the scientists cannot predict an outbreak quite accurately. "But the three investigation methods give us indications of when it could become acute," Wieber explains. "If it continues as it is now, we are talking about several tens of thousands of years." Should the development accelerate, the scientists would of course have to reassess. "At the moment, however, the traffic light is still green."

(Original text: Sandra Liermann; Translation: Mareike Graepel)