Researchers from Heidelberg and Mainz precisely date devastating volcanic eruption / Central European Late Glacial climate change in the Younger Dryas was not a consequence of the Laacher See eruption
21 January 2025
During the eruption of the Laacher See volcano more than 13,000 years ago, gigantic quantities of ash and pumice were expelled that formed meter-thick deposits in the Rhine valley and adjacent regions. Volcanic ash from the eruption reached as far as France, northern Italy, and Scandinavia. Researchers have now been able to detect and precisely date the eruption with the help of a stalagmite in the Herbstlabyrinth cave in the Westerwald in central Germany. "This allows us to synchronize the Greenland ice core record with the data from other terrestrial climate archives in Europe," said Professor Denis Scholz, head of the Isotope-geochemical Palaeoclimatology / Speleothem Research group at the Institute of Geosciences of Johannes Gutenberg University Mainz (JGU). The paleoclimate researcher and his team were involved in a joint research project with Heidelberg University. Their findings have recently been published in Science Advances.
Search for the causes of abrupt climatic change
The analysis of abrupt past climate changes might help to assess the potential impact of the current melting of Arctic ice. Roughly 13,000 years ago, at the beginning of the Younger Dryas, the Atlantic-European realm experienced an abrupt relapse to near-glacial climate conditions. It is unclear how rapidly the effects propagated southwards across Europe because the chronologies of climate archives from the European mainland and the ice cores are not adequately synchronized. Ice cores obtained in Greenland represent an important climate archive and their paleoclimatic data provide very valuable information about the Earth's climate history.
The eruption of the Laacher See volcano in the Eifel volcanic field in Germany is postulated as one of the potential causes of the extensive cooling during the Younger Dryas. The Laacher See is located some 100 kilometers from the Herbstlabyrinth cave system. During the sulfur-rich volcanic eruption, fragments of the materials ejected into the air were deposited above the cave. The researchers now systematically examined a roughly 15-centimeter-long stalagmite from the cave for evidence of this eruption. Stalagmites are rock formations that grow from the floor of a cave. They are particularly suitable for paleoclimate research as they tend to grow more regularly than stalactites that hang from cave ceilings.
Herbstlabyrinth stalagmite contains sulfur from the eruption
"We found a major peak of sulfur in the stalagmite that we interpret as a definite trace of the eruption of the Laacher See volcano," said Dr. Michael Weber, a member of Scholz's research group and co-author of the paper. "It is quite extraordinary when you search for evidence of a specific volcanic eruption in a stalagmite and then actually discover those signs," added Weber.
The researchers also compared their results with the data from Greenland ice cores. "The real highlight was our finding that the sulfur peak from the Herbstlabyrinth can be unequivocally linked to a sulfur peak in the Greenland ice core record. This has never been done before," said Professor Denis Scholz. During a volcanic eruption, sulfur is expelled into the atmosphere where it is dispersed by the winds and can be deposited on existing ice surfaces, which is exactly what happened in the case of the Laacher See eruption. As the two climate archives have now been synchronized, this enables researchers to date the eruption to about 13,008 years Before Present (BP), whereby this refers to the year 1950. "We have managed to synchronize the timescales of the Greenland ice cores with those of other European climate archives with the aid of the Laacher See eruption," said Scholz.
The results reported in Science Advances, with lead author Dr. Sophie Warken of Heidelberg University, a former doctoral candidate supervised by Professor Denis Scholz at JGU, provide unquestionable evidence that the Laacher See volcanic eruption occurred about 150 years before the onset of the Younger Dryas cold period and therefore could not be responsible for it. "We can now definitively rule out any causal link between the two events," concluded Scholz.
Collaboration between researchers from Germany, Australia, and Switzerland
The research project and the paper "Discovery of Laacher See eruption in speleothem record synchronizes Greenland and central European late Glacial climate change" is a collaboration of Heidelberg University as the coordinating institution, Johannes Gutenberg University Mainz, Curtin University in Australia, and the University of Bern in Switzerland. The research was supported by the Terrestrial Magmatic Systems (TeMaS) collaborative project of JGU, Goethe University Frankfurt, and Heidelberg University.