Scientists Detect Hundreds of Deep Micro-Earthquakes Beneath Germany’s Laacher See Volcano

Germany experiences frequent seismic activity, though much of it goes unnoticed. These tremors typically originate deep underground and register at low frequencies.

Beneath the surface, however, researchers suspect that something may be shifting. Scientists monitoring Lake Laach in Germany’s western Eifel region over recent years have documented unusual geological behaviour.

Between September 2022 and August 2023, monitoring stations recorded more than 500 micro-earthquakes beneath the lake, which fills the crater of a volcano that last erupted approximately 13,000 years ago.

Germany’s Most Powerful Volcano

That prehistoric eruption was so immense that ash travelled as far as Sweden and northern Italy. Experts continue to call for ongoing surveillance of the site.

Multiple studies have confirmed persistent underground activity. A renewed increase in seismic events was reported in the Eastern Eifel in October 2025, building on findings from a 2019 study.

Scientists classify these movements as deep low-frequency earthquakes (DLF). Such tremors are considered potential indicators that the Laacher See volcano could eventually erupt again.

Investigations centre on Lake Laach in Rhineland-Palatinate, the largest lake in the federal state.

The area is aptly named the Volcanic Eifel; the Eastern Eifel alone contains roughly 100 volcanoes.

“DLF earthquakes are regarded worldwide as an indication of the movement of magmatic fluids at great depth,” explains Torsten Dahm, head of the Earthquake and Volcano Physics section at the GFZ. “Under active volcanoes, for example in Iceland, Japan or Kamchatka, such earthquakes can be observed regularly.”

According to the research, magmatic fluids appear to be accumulating at depths of approximately 12 to 14 kilometres. These fluids include water, oxygen, sulphur compounds and halogens released from molten rock, and they play a decisive role in determining the explosiveness of any future eruption. Their migration can also induce seismic events underground.

Researchers believe these fluids may ascend from the upper mantle into the Earth’s crust via the Ochtendung fault zone, providing evidence that the volcanic system beneath Lake Laach remains active.

The findings also suggest the existence of magma chambers in the crust beneath the lake, potentially in the process of slowly refilling.

On the night of 10 October 2025, an unusual earthquake swarm produced roughly 92 small tremors within twelve hours. The strongest registered a magnitude of just 0.9.

“In total, four spatially confined clusters of such DLF earthquakes have been detected in the Eastern Eifel over the past five years,” noted lead author Martin Hensch from the Association of State Seismological Services.

Despite the activity, researchers do not anticipate a volcanic eruption in the foreseeable future. Dating of the magma from the last eruption indicates that approximately 30,000 years were required to fill the upper magma chamber before that event occurred.

“The ascent of magma into the shallow crust is almost always accompanied by high-frequency earthquake swarms. Such activity has not yet been observed in the Eastern Eifel,” said Joachim Ritter from the Geophysical Institute at KIT.

“Moreover, there is no evidence of uplift of the Earth’s surface, which would have to be clearly detectable in the event of massive magma ascent,” adds Dahm.

Beyond the recorded tremors, ongoing CO2 degassing from the mantle provides further evidence of subterranean processes.

In 2024, the GFZ conducted RMT measurements at two sites around Lake Laach, detecting CO2 emissions of magmatic origin at both locations. Taken together, these observations point to active geological processes below the surface.

From September 2022 to August 2023, geologists documented more than 500 local micro-earthquakes in a study published in 2026. During these events, the rock is hydraulically fractured, a process the researchers describe as natural hydraulic fracking.

The team also identified a likely reservoir structure, potentially a magma chamber, at a depth of 12 to 14 kilometres. This structure extends horizontally over 15 kilometres beneath the active seismic zone.

An Ice Age Eruption

The Eifel volcano erupted during the Ice Age. Recent reanalysis places the event at 13,084 years ago, approximately 184 years earlier than previously estimated.

The eruption was massive. Ash columns are believed to have risen into the stratosphere, reaching altitudes of up to 30 kilometres. Prevailing winds carried the ash thousands of kilometres, north to Sweden and south to northern Italy. The explosive force is now estimated to equal approximately 500 Hiroshima bombs.

Volcanic ash and pumice created a seven-metre-thick deposit in the Rhine valley. Near the volcano, layers reached thicknesses of around 60 metres, while in the modern Cologne-Bonn region ash accumulated to depths of up to one metre.

Lake Laach formed only after this cataclysmic event. The eruption lasted ten days, punctuated by periods of relative calm. Hot gases shattered basement rock and ancient lava flows upon contacting groundwater, clearing pathways for rising magma.

To refine the eruption date, a research team from the universities of Mainz, Frankfurt and Heidelberg examined sulphur deposits in natural climate archives. They identified evidence both in a Greenland ice core and in a stalagmite from a cave in the Westerwald, using sulphate concentrations as a key indicator.

The volcanic rock produced during the eruption was later quarried and used, among other purposes, as building material in the 19th century.

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