Germany's Lake Laach volcano, long considered dormant, has recently exhibited signs of activity, with over 1,000 tiny earthquakes recorded. These quakes have revealed a deeper, slanted reservoir beneath the lake, a surprising discovery that challenges previous assumptions. The new data suggests an active underground system that may still be building pressure, a development that warrants close monitoring.
The earthquakes are concentrated in a narrow zone between Ochtendung and Lake Laach, indicating a complex fault system. Torsten Dahm's team at the GFZ Helmholtz Centre for Geosciences used advanced sensor networks and fiber-optic cables to map this buried system. The reservoir is tilted towards the Neuwied Basin, a valley on the Rhine, where many small quakes have been detected.
While the geometry doesn't prove an imminent eruption, it highlights a dynamic system that could be building pressure. The quakes are consistent with a system influenced by moving fluids, as pressure can weaken rock and cause faults to slip. However, some quakes near the fault zone's southern step resemble standard aftershocks, suggesting a more complex picture.
The study also uncovered unusual seismic reflections pointing to magmatic fluids, hot gases, and liquids released by melt, pooling between rock layers. The strength of these reflections indicates significant fluid accumulation, but the nature of these fluids (magma or magmatic fluids) remains uncertain. This uncertainty is crucial for hazard assessment, as pressurized melt behaves differently from gas or water in cracks.
Previous clues, such as gas studies at nearby mineral springs and deeper rumblings beneath the volcano, hint at active fluid pathways. These findings, combined with the new earthquake map, suggest a more comprehensive understanding of the volcanic system. The reservoir's tilt and the quakes' distribution along one side of the lake may explain why quakes are not evenly distributed.
The study also highlights the importance of sharper maps in volcanic fields. These maps can guide gas monitoring, earthquake watch lists, and land-use planning, helping to distinguish between ordinary tectonic earthquakes and signs of molten material or hot fluids. However, the model doesn't prove overpressure, and pre-existing weak zones in the crust could also influence the quakes.
In conclusion, the new data on Lake Laach volcano provides a new baseline for the Eifel region. The volcano, once considered dormant, now appears less dormant when considering the thousands of tiny quakes, older gas clues, and the tilted reservoir. This improved understanding allows for better judgment of future unrest, emphasizing the need for continued monitoring and research.
